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View Full Version : 1227747 to 16197427 Conversion PCM Swap with Wiring Pinout Directions!



EagleMark
05-29-2011, 06:17 PM
I stole this information from Dave W. Writeup on CK5
http://coloradok5.com/forums/showthread.php?t=270253

He also got information from Thirdgen.org to start and I think the origanal was written by Fast355
http://www.thirdgen.org/techboard/tbi/4 ... g-tbi.html (http://www.thirdgen.org/techboard/tbi/442325-notes-information-converting-tbi.html)

Since I'm wiring one up starting today I figured I post up here the one Dave has added notes to.
dave w

Notes and information on converting to a TBI PCM

I have had multiple people ask about re-pinning their earlier TBI cars/trucks
to use the latest PCM. So here is the result. Information regarding the swap.

PCM Swap/Tuning Notes
8746/6965/7747/299 to 427 Truck PCM (Car showed, Trucks VERY similar)

Old Pin---New Pin-----Color---------Function
A1--------F6----------GRN/WHT------Fuel Pump Relay Control
A3--------F16---------DK GRN/YEL---Charcoal Canister Purge Solenoid *** Not used on 87 GMC W/454***
A4--------E1----------GRY-------------EGR Control
A5--------E6----------BRN/WHT------Service Engine Soon Light
A6--------E15---------PNK/BLK-------Ignition Feed +12VDC
A7--------(1*)--------TAN/BLK-------TCC/Shift Light *** Investigate***
A8--------F9----------ORN-------------Serial Datastream
A9--------A14--------WHT/BLK-------Diagnostic Test
A10-------F13--------BRN-------------Vehicle Speed Signal ***Output Speed not from DRAC set***
A11-------B3---------BLK--------------Sensor Ground
A12-------A1---------BLK/WHT-------ECM Ground 1
B1--------E16--------ORN-------------Battery +12VDC
B2--------B12--------TAN/WHT-------Fuel Pump Signal
B3--------A5---------BLK/RED--------EST Ref Low
B5--------A4---------PPL/WHT--------EST Ref High
B6--------?-----------PPL---------------VATS(2*) *** Not used on 87 GMC W/454***
B7--------(3*)-------BLK---------------Knock Sensor *** Not used on 87 GMC W/454***
B8--------E12--------LT BLUE---------A/C Clutch Signal ***GRN Not LT BLUE 87 GMC W/454***
B10-------E5---------ORN/BLK--------Park/Neutral Switch ***Investigate***
C1--------(4*)-------BLK/PNK---------A.I.R. Converter Solenoid *** Not used on 87 GMC W/454***
C2--------E7---------BRN---------------A.I.R. Port Solenoid (Diverter in trucks) ***Investigate***
C3--------A7---------LT GRN/BLK-----IAC "B" Low ***LT GRN-BLK on 87 GMC W/454*** --- A7 1995 7.4
C4--------A8---------LT GRN/WHT----IAC "B" High ***C4 WHT EST SIGNAL on 87 GMC W/454*** F11 1995 7.4
C5--------A3---------LT BLU/WHT-----IAC "A" High ***C5 LT GRN-WHT on 87 GMC W/454*** --- A8 1995 7.4
C6--------A6---------LT BLU/BLK------IAC "A" Low ***C6 LT BLU-WHT 87 GMC W/454*** --- A3 1995 7.4
C7--------(5*)-------LT BLU------------High Gear Switch (In Auto Trans) ***C7 LT BLU-BLK on 87 GMC W/454*** --- A6 1995 7.4
C8--------(6*)-------LT BLU------------Power Steering Pressure Switch ***Not used on 87 GMC W/454***
C9--------(7*)-------PPL/WHT---------Crank Signal
C10-------B8--------YEL----------------Coolant Temperature Signal
C11-------B13-------LT GRN-----------MAP Signal
C12-------B9--------Tan----------------MAT Signal(8*) *** Not used on 87 GMC W/454*** ***ALSO NOT SHOWN ON DIAGRAMS BELOW***
C13-------A15-------DK BLUE---------TPS Signal
C14-------E14-------GRY---------------5 Volt Reference
C15/D14--A9--------DRK GRN--------Injector "2" Control *** D14 on 87 GMC W/454***
C16------E13--------Orange-----------Battery (Inputed in place of Brake Switchfor TCC to function)
D1-------A2----------BLK/WHT--------ECM Ground 2 *** TAN-WHT on 87 GMC W/454***
D2-------B4----------PPL---------------MAP Sensor Ground
D4-------F11--------WHT--------------EST Signal
D5-------B2---------TAN/BLK---------EST Bypass
D6-------A12--------TAN--------------O2 Sensor Ground
D7-------A10--------PPL---------------02 Sensor Signal
D15/D16--A16-----DK BLUE---------Injector "1" Control ***D16 on 87 GMC W/454***
none ---- F8 -------unknown---------For Power steering switch input. (gregs78cam post 10)

Swap Notes
*** Throttle Kicker Enable disabled***
*** Initiate Integral with Calibration Const. Not Running enabled ***
(1*)= Use E2 for a shift light on a manual transmission or E11 for the TCC onan Automatic
(2*)= Supported by the PCM if optioned in the Prom on an UNKNOWN pin
(3*)= A.) Wire like 1995 P30 Step Van, ESC Module output to B7
(3*)= B.) Wire like 1995 C10 Truck, Bypass ESC (Blue to Brown) and useLate TBI/TPI 305/350 Knock sensor
(4*)= Air injection into converter not used on trucks, but PCM has severalother un-used outputs (Tuning Valve, Idle Kicker)
(5*)= Not Used by PCM (I like to leave the small connector in place and pinin unused wires)
(6*)= Supported by PCM if optioned in the Prom on an UNKNOWN pin(1994-1995 2.2 S10 Wiring Diagram anyone?)
(7*)= Not used by PCM, Remove 3 amp "CRANK" fuse from fuse box andstore in small connector)
(8*)= Supported by the PCM, but functionality will need to be enabled in theProm6965 ONLY- Will have a NC relay that the computer grounds to shut-off theA/C compressor when the engine is heavily loaded. The A/C will work eitherby removing the wire all-togather, or connecting it to pin E3 (A/C Cut-Off orCPI Tuning Valve output)

I would also like to mention that the orange Serial Data wire needs to berelocated from the top row, Pin "E" to the lower row, Pin "M". You will alsoneed to scan the vehicle like a 1993-1995 G-Series Van, C-Series Truck,S-Series Blazer, etc with Auto transmission.

Finally, this is a trick Haulin@$$ taught me, if you have a wideband and arelooking to get real-time AFR put into the datastream, hook the 0-5 volt signalinto pin B16 (Linear EGR pintle position feedback). With some adaption to theALDL Definition being used to decode the reading, you can get an AFR
reading of 10-20:1 or so.

EagleMark
06-07-2011, 08:09 PM
Wiring Diagrams for the 16197427 and 16197395

[attachment=0:q15r09ib]427-1.gif[/attachment:q15r09ib]

[attachment=1:q15r09ib]427-2.gif[/attachment:q15r09ib]

[attachment=2:q15r09ib]427-3.gif[/attachment:q15r09ib]

EagleMark
06-08-2011, 05:15 PM
Does anyone know how the shift light works on a manaul from pin A7 (7747) to E2 (427)? Is it set to come on at certain RPM?

1leg
02-06-2012, 03:01 PM
Would this swap be very similer if you used the 8625 PCM.

EagleMark
02-06-2012, 03:36 PM
Would this swap be very similer if you used the 8625 PCM.Yup. Basically same PCM $OD, $OE, $E6, $31.
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?336-16168625-PCM-Information-E6

93V8S10
02-06-2012, 07:46 PM
Does anyone know how the shift light works on a manaul from pin A7 (7747) to E2 (427)? Is it set to come on at certain RPM?
With the 427 it will come on at a certain RPM + a whole bunch of other parameters.

EagleMark
02-07-2012, 02:11 AM
I had forgot about this, harness was done months ago, going in truck Thursday so I have time to wire this in! :thumbsup:

one92rs
02-07-2012, 07:31 PM
so does anyone know the pin in the 427 for the power steering pressure switch?

1leg
02-07-2012, 07:59 PM
What bin would you start with on 350 and th400 trans and 4-11 gears when doing this swap. yep just bought a 427.

gregs78cam
02-07-2012, 08:48 PM
I have been looking for it for about a half hour now, I can tell you the PCM sees the input at IAC Mode Word #2, L4E86 bit 1.

From thirdgen from MarcusMandarino

"Fast355

I found the info about PSPS on Chilton's, page 6-60, 2.2L > F8

Marcus"

EagleMark EDIT: none ---- F8 -------unknown---------For Power steering switch input. (greags78cam post 10)
added to chart.

gregs78cam
02-07-2012, 09:01 PM
Might try this, and just uncheck TCC only. But you would need to set up something for the kickdown. I think dave w had something figured out in the .bin to use a PCM output to kickdown. Try a search.

93V8S10
02-07-2012, 09:44 PM
I have been looking for it for about a half hour now, I can tell you the PCM sees the input at IAC Mode Word #2, L4E86 bit 1.

From thirdgen from MarcusMandarino

"Fast355

I found the info about PSPS on Chilton's, page 6-60, 2.2L > F8

Marcus"
I've always been skeptical of that answer, since that pin is used with 4wd, so I just order a 1994 GM service manual. Should have a answer in a couple weeks.

gregs78cam
02-07-2012, 10:08 PM
AAHHHH. I would test it if I had a way. What does the switch put through on this wire?

EagleMark
02-07-2012, 10:26 PM
AAHHHH. I would test it if I had a way. What does the switch put through on this wire?I don't know but I have one that works and shows when in use in adx on my LT1.

93V8S10
02-13-2012, 08:07 PM
Got the new book in today, and F8 is the correct pin for the power steering switch. Also, fount out that B1 is for the DIS system used with the 2.2L. It is called the 1X Signal, and is used for ASDF (Alternate Synchronous Double Fire).

Anyone ever find the VATS pin? I'll trade you the AC High Pressure Switch pin. This was used to raise the idle if the A/C pressure got too high (no bins that I know of with this active).

gregs78cam
02-13-2012, 08:16 PM
Sounds like that book has some good info in it. It there anything in there that could make sense of this trans datastream portion of the hac?


L53F3 FDB $0010 ; 11, MALFFLG6, ERROR WD 6
;
; b7 1 = ERR 57. (not used)
; b6 1 = ERR 58, XMISH TEMP HI
; b5 1 = ERR 59, XMISH TEMP LOW
; b4 1 = ERR 61, TURBO BOOST SENSOR HI
;
; b3 1 = ERR 62, TURBO BOOST SENSOR LOW
; b2 1 = ERR 63, BARO SENSOR HI
; b1 1 = ERR 64, BARO SENSOR LOW
; b0 1 = ERR 65. (not used)
;-----------------------------
L53F5 FDB $001B ; 12, CURMALF5, CURRENT ERROR WD 6
;
; b7 1 = ERR 57. (not used)
; b6 1 = ERR 58, XMISH TEMP HI
; b5 1 = ERR 59, XMISH TEMP LOW
; b4 1 = ERR 61, TURBO BOOST SENSOR HI
;
; b3 1 = ERR 62, TURBO BOOST SENSOR LOW
; b2 1 = ERR 63, BARO SENSOR HI
; b1 1 = ERR 64, BARO SENSOR LOW
; b0 1 = ERR 65. (not used)
;-----------------------------

I was thinking it might be something used in the diesel engine TCM.

Can you shed any more info on any unlisted I/O pins?

93V8S10
02-13-2012, 08:27 PM
Nothing about diesel engines, the new book is the S/T Driveability & Emissions Manual. I've woundered about those too.

Here's what I've got so far:

EagleMark
02-13-2012, 08:46 PM
Looks like that transmission code was also used in a diesel application. Im my LT1 it is simalar to these PCM that it has engine data and transmission data although I have them in same adx, need to change connection and montitor. Transmission data also shows some engine data and all error codes.

EagleMark
02-13-2012, 08:49 PM
Also, found out that B1 is for the DIS system used with the 2.2L. It is called the 1X Signal, and is used for ASDF (Alternate Synchronous Double Fire).
So when is the DIS hac coming out for V8? :innocent2:

JeepsAndGuns
02-14-2012, 05:33 AM
So when is the DIS hac coming out for V8? :innocent2:

I havent forgotten or abandoned the northstar DIS we talked about a couple months ago. Once I get my MPFI installed and tuned, DIS comes next. :rockon:
So I'm intrested in DIS info too.

1project2many
02-14-2012, 05:34 AM
Very interesting that GM found ASDF to produce cleaner emissions in the S10. In some masks ASDF is a function of IPW to prevent commanded on times less than injector is capable of and is implemented without 1X signal. In these cases ASDF is not implemented during most operating conditions. It's noteworthy that GM resorted to hardware solution in 7427. I'd love to have more time to investigate the hardware relationship between the 1X input pin, memcal configuration, and limp mode fueling.

The list of unused pins has been pretty consistent in all of the models I've looked at. A11,A13, B6,B7, B11, B14, E7, F4,F5. Checking multpile vehicles to see if this list can be shortened might be a worthwhile approach.

93V8S10
02-14-2012, 05:23 PM
So when is the DIS hac coming out for V8? :innocent2:
LOL, way over my head.


A13 is the A/C high Pressure Switch
E7 is AIR Bypass Control
I'm still uncertain about whether B7 can be used for the underhood ESC.

I'd bet on B11 or B14 being VATS.

one92rs
02-14-2012, 06:12 PM
now the vats deal would be cool. since i have it in a 92 camaro it would be cool to have it wired up as well.

Scorp1us
03-14-2012, 10:09 AM
We should update the GIF on the front page to t he revised version found here: http://www.thirdgen.org/techboard/posts/diy-prom/409230-16197427-700r4-tcc/3243682-post40.html

Notably, the P/N switch is updated. I've been beating my head against a wall because my IAC isn't working right. Because I don't have the wire hooked up, because it was not on the sheet. It was not grounded so it thought it was in drive and would not do the pintle thing.

EagleMark
03-14-2012, 10:30 AM
Thank you and done! :thumbsup:

1project2many
08-12-2012, 08:09 PM
I have checked the pinout on the first page and cross checked factory pinouts from C/K and S/T vehicles using the same PCM family with manual transmissions. I see no park/neutral switch input or grounded signal wire listed in the OEM diagrams. Also, the two factory diagrams I have show both VSS and trans speed signals connected to the pcm in manual trans applications.

Does anyone have confirmation of P/N input on E5, or of the results of not including the VSS / trans speed signal on F13?
Thanks

Six_Shooter
08-12-2012, 08:35 PM
The '7427 does not use a nuetral safety switch input.

What it does use is the gear select inputs to determine what gear the trans shifter is in. I don't remember the combination of on's and off's of those three inputs to detect what gear is selected, but I know it's in some of the EFI manuals from OTC and Snap On IIRC.

1project2many
08-12-2012, 08:57 PM
Right. Whoops... this was specifically related to manual trans applications. Previous post edited for clarity. :)

dave w
08-12-2012, 08:57 PM
Does anyone have confirmation of P/N input on A5, or of the results of not including the VSS / trans speed signal on F13?
Thanks

On my '427 PCM schematics, A5 is Distributor Reference Low (Ground). I personally don't like the idea of grounding the P/N wire to Ground. On the '7747 to '427 PCM conversions I've done, I covered the P/N wire with heat shrink tubing and zipped tied the P/N wire to the harness.

The challenge I see to using a '427 PCM without a VSS is being able program which Spark / Fuel tables (Near Idle / Off Idle) for the PCM to use. I'm thinking without a VSS input, the '427 PCM will always think the vehicle speed is ZERO MPH. The '427 PCM could be programmed to switch from near idle / off idle, Spark / Fuel tables by TPS% only? I've never tried using TPS% only programming on the '427.

dave w

1project2many
08-12-2012, 09:05 PM
The pin in question was E5. Range switch C. I need a better proofreader. :(


On the '7747 to '427 PCM conversions I've done, I covered the P/N wire with heat shrink tubing and zipped tied the P/N wire to the harness.
That matches the manual trans wiring diagrams.

Those diagrams also show two signals from the DRAC. One is VSS and one is trans speed. The "possible symptom" for a faulty trans speed signal on F13 is "fuel cut." I have a 4k ppm VSS signal to supply. I do not have a 40 pulse/revolution trans speed signal.

dave w
08-12-2012, 09:14 PM
The '7747 is a 2K PPM VSS. The '427 is happy with a 2K PMM input to pin F13. The only time I needed 40 pulses / revolution was for an electronic overdrive transmission conversion.

dave w

EagleMark
08-12-2012, 09:58 PM
The challenge I see to using a '427 PCM without a VSS is being able program which Spark / Fuel tables (Near Idle / Off Idle) for the PCM to use. I'm thinking without a VSS input, the '427 PCM will always think the vehicle speed is ZERO MPH. The '427 PCM could be programmed to switch from near idle / off idle, Spark / Fuel tables by TPS% only? I've never tried using TPS% only programming on the '427.

dave wI've done this and is working quite well. I did it because someone elsewhere said it could not be done. That said I will never do it again to save $80 for a VSS... way to many hours tuning to work out bugs...

belaw
08-13-2012, 08:04 AM
The '7747 is a 2K PPM VSS. The '427 is happy with a 2K PMM input to pin F13. The only time I needed 40 pulses / revolution was for an electronic overdrive transmission conversion.

dave w

What is the normal input from the VSSB to pin F13 on the '7427? Some sources say 2k PPM, but others say 4k PPM. And when do you need to set the "Output Speed not from DRAC" flag?

dave w
08-13-2012, 10:18 AM
What is the normal input from the VSSB to pin F13 on the '7427? Some sources say 2k PPM, but others say 4k PPM. And when do you need to set the "Output Speed not from DRAC" flag?

I've never measured the normal input to pin F13 from the VSSB. It seems to me, 2K is the expected input to pin F13 on the '427 PCM. I've only done the '427 PCM to vehicles that had either a '7747 / '8747 ECM's. As far as I know, the '7747 / '8747 have always been 2K VSS. I've never really noticed any difference when setting "Output Speed not from Drac" flag on the '427 PCM upgrades I've done. In the absense of "Factory Information" I've "Set" the "Output Speed not from Drac" on the '7747 / '8747 TBI PCM upgrades I've done.

dave w

CDeeZ
08-13-2012, 10:22 AM
What is the normal input from the VSSB to pin F13 on the '7427? Some sources say 2k PPM, but others say 4k PPM. And when do you need to set the "Output Speed not from DRAC" flag?

Brian,

I think it depended on your original application. I believe 4K is the more common, but 2K is doable, and then check that flag "output sped not from DRAC"





As far as the P/N switch: Since my C1500 was originally a 7747 ECM, it had a P/N switch on the end of the column, under the dash, inside the cab. When I still had the 7747 in there, I hooked up my laptop and when I unplugged the P/N switch entirely it showed as being in "Drive" all the time that way. (T-56 here BTW) I've left the P/N switch unplugged since swapping to the 7427.




The '7747 is a 2K PPM VSS. The '427 is happy with a 2K PMM input to pin F13. The only time I needed 40 pulses / revolution was for an electronic overdrive transmission conversion.

dave w



Dave, how exactly did you do the 2K PPM vs the 4K PPM???

dave w
08-13-2012, 11:01 AM
Dave, how exactly did you do the 2K PPM vs the 4K PPM???

The VSS information from JTR, http://www.jagsthatrun.com/SpeedSensors_Order.html shows early Pickup TBI ('7747 / ' 8747) is 2K PPM.

I've never tried to use the 4K PPM on a '427 PCM. The 4K PPM might work on the '427, but I don't have any personal experience doing so.

dave w

1project2many
08-13-2012, 01:09 PM
Yes, 7747 applications expect 2k ppm. They were developed when the speedometer cable drove the speed sensor. I can cross check a 7427 wiring diagram against the DRAC outputs to determine speed signal frequency on F13. The "output speed not from DRAC" selection might be shown in the manual trans comparison thread currently running?

EagleMark
08-13-2012, 02:53 PM
FYI DRAC on 1227747 and VSSB on 16197427 and they do not interchange.

JeepsAndGuns
08-13-2012, 02:58 PM
I know on mine, it did not read on the datalog dash untill I selected "vss not from drac". Once I did it started working. I am using the JTR 2ppm vss.

FSJ Guy
08-13-2012, 07:42 PM
I know on mine, it did not read on the datalog dash untill I selected "vss not from drac". Once I did it started working. I am using the JTR 2ppm vss.

X2.

(Extra letters because X2 is simply too short.)

1project2many
08-14-2012, 04:32 AM
VSSB is a type of DRAC. Original reprogramming docs didn't even say "VSSB". All my data shows the "white box" versions are plug compatible but if you have something different I've got an open mind. Earlier trucks had DRAC built into the back of the dash and was programmed with a special fuses instead of resistors. Reprogramming meant popping all the fuses then installing a specal programming key which was nothing more than a series of jumpers. I've seen some vehicles where dash programming clip is set for "divide by" ratio of 1 and white box DRAC is installed.

EagleMark
08-14-2012, 09:05 AM
Well they are both white boxs and they both have the same plug. But inside DRAC is one set of jumpers, inside VSSB is 2 sets of jumpers. If you plug a DRAC into a VSSB system it melts the new DIP switch. I haven't done much testing after that...

Six_Shooter
08-14-2012, 09:26 AM
I think you had other issues, since I haven't heard of anyone else having that issue.

1project2many
08-14-2012, 09:56 AM
If you plug a DRAC into a VSSB system it melts the new DIP switch. I haven't done much testing after that...
No?? Can't imagine why not. :innocent2:


I've never had problems swapping them around before. Maybe a blob of solder in the wrong place?

CDeeZ
08-14-2012, 11:42 AM
The VSS information from JTR, http://www.jagsthatrun.com/SpeedSensors_Order.html shows early Pickup TBI ('7747 / ' 8747) is 2K PPM.

I've never tried to use the 4K PPM on a '427 PCM. The 4K PPM might work on the '427, but I don't have any personal experience doing so.

dave w

Wow, and here I thought all this time I have a 4K system in my '90 C-1500. BTW, PPM means pulses per mile correct?




Yes, 7747 applications expect 2k ppm. They were developed when the speedometer cable drove the speed sensor. I can cross check a 7427 wiring diagram against the DRAC outputs to determine speed signal frequency on F13. The "output speed not from DRAC" selection might be shown in the manual trans comparison thread currently running?

Does this mean that my C1500 that was originally a 7747 system is 2K PPM, the reason I ask is because on my application it never was a cable driven speedo. I need to boot into the windows side of my HDD when I get back to have another look at all that info as far as the comparo, wondering if maybe I should have that flag checked since I'm manual trans.



FYI DRAC on 1227747 and VSSB on 16197427 and they do not interchange.

Well the 7 jumper and 14 jumper versions are interchangeable, but on my 7747 the original gauges had the DRAC built into the cluster itself, not a stand alone unit so that is obviously not interchangeable with anything, not easily anyways. The white boxes all interchange though. I think the VSSB/DRAC is basically a nomenclature difference, nothing more. Technically the DRAC is the 7 jumper variant and it was produced from '90-'91 as a stand alone white box unit. Earlier applications using "DRACs" may have incorporated the DRAC into the cluster as my original "moonie" gauges did in my truck. The 14 jumper version is the VSSB and it was produced from '92-'95


VSSB is a type of DRAC. Original reprogramming docs didn't even say "VSSB". All my data shows the "white box" versions are plug compatible but if you have something different I've got an open mind. Earlier trucks had DRAC built into the back of the dash and was programmed with a special fuses instead of resistors. Reprogramming meant popping all the fuses then installing a specal programming key which was nothing more than a series of jumpers. I've seen some vehicles where dash programming clip is set for "divide by" ratio of 1 and white box DRAC is installed.

I like how descriptive "white box" is http://www.gearhead-efi.com/Fuel-Injection/images/smilies/laughing2.gif Yes I went through that very thing, my truck had what are referred to as the "moonies" gauges and the DRAC is built into the cluster itself... I just desoldered those "fuses" and recalibrated the DRAC for my 4.88 gears by using some high tech jumpers fashioned out of a butchered paperclip. I recently swapped to the "needles" gauges from like a 94/95 C1500 and those did use the stand alone DRAC/VSSB/white box lol, whatever ya wanna call it. While we are on the topic of this I wanted to mention that during my research for how to wire the DRAC, and new gauges and everything, I stumbled across all kinds of conflicting and/or vague information. What I could gather is that the DRACs/VSSBs are basically all pretty similar, they all perform the same function of converting the incoming VSS signal from AC to calibrated DC signal. Some DRACs have slightly different wire locations: for example, occasionally the cruise signal wire from the DRAC is off on a 2nd plug by itself instead of pinned in with the rest of the wires in the main plug. Some have TWO outputs for VSS to the PCM (VSS and TRANS OUTPUT SPEED) and some others I've seen only have one output to PCM/ECM for VSS.



Well they are both white boxs and they both have the same plug. But inside DRAC is one set of jumpers, inside VSSB is 2 sets of jumpers. If you plug a DRAC into a VSSB system it melts the new DIP switch. I haven't done much testing after that...

Some of them have two plugs. I have used both DRAC and VSSB in my 90 C1500 without issue. Both with DIP switches.


I think you had other issues, since I haven't heard of anyone else having that issue.

Yeah I haven't heard of anyone either.


No?? Can't imagine why not. http://www.gearhead-efi.com/Fuel-Injection/images/smilies/innocent2.gif


I've never had problems swapping them around before. Maybe a blob of solder in the wrong place?


Very possible. Possibly the unit itself just crapped out?






I use VSSB and DRAC interchangeably, the function is basically the same between them. The one problem I can see with the DIP switch install is that with the white case closed, it seems awful close to the rockers on the DIP switch. I don't know if the particular DIPs they had at my local radioshack were bigger than normal or what, but I think I'm going to take one of my extra DRACs and just set it up with jumpers, its not like it's that hard to move the jumpers around if you have too. And if you don't change tires and gears every weekend I don't know if there is really much point to a DIP after having gone to the trouble to install a few DIPs myself.


Alot of the DRACs I've seen have a DK BLUE wire that is used for VSS output. These DRACs also typically have a 2nd brown wire (main brown wire is +12v for DRAC). Here is where it gets interesting: I opted to use the 7 jumper version the "DRAC" that I had laying around. This DRAC didn't have the DK BLUE wire at all, only the 2nd brown wire. I took the connector off and pulled the plastic comb off and ADDED the DK BLUE wire to a DRAC that didn't originally have it. Both (DK BLUE and the 2nd BROWN) appear to be VSS output signal for PCM: VSS and Trans Output Speed... Initially after swapping to the 7427 I kept getting "LOW TRANS OUTPUT SPEED" error. After connecting the BK BLUE and BROWN wire from the DRAC to the PCM at the respective pins, the code never came back.

1project2many
08-14-2012, 02:11 PM
If you look around the web, or on this site, you might find a PDF called drac2 with calibration info and pictures and even a pinout. There are scanned documents with fingerprint smudges that show jumper settings for the various "divide by" ratios and images of the two DRAC circuit types. Had I known I'd be uploading those papers to the web in '97, I wouldn't have smudged them back in '93. In '98 or '99 a fellow with some technical writing experience took the original drac.pdf, basically a collection of technician's notes, and re-wrote it as a more presentable paper (drac2). That document also introduced the DIP switch. The included pinout was put together later, maybe in late 99 or 2000 and has a disclaimer as to accuracy. When I researched the pinout I'd often find that a wire or signal had different names in different vehicles but when I'd dig into the service manual the signal itself was consistent. But without a statistically significant sample I wasn't willing to skip the disclaimer. I haven't spoken with too many people who have actually checked these signals. I had two units to test on a bench and both produced signals which matched the pinout. When someone complains to me that they have a unit which doesn't match the pinout it's usually because their service manual calls the signal by another name. It would be awesome if someone either found OE documentation or had enough time and energy to do some component testing so the pinout could be confirmed or removed.

"White box" is a simple identifier but with some dealership background and some years working on these, I know there are speedometer buffers, ratio adapters, signal buffers, digital converters, and plenty of other monikers that have been applied in service literature. Experience has shown that the green box is the green box, and the yellow box is the yellow box, and the orange box is the orange box, and the blue box is the blue box, no matter what make and model it originally came in. Skip all the service manual nomenclature, just go to the junkyard and get the right color box and you're done.

Speedometer cables were standardized at 1000 revolutions per mile. Original speed sensors were two shutter wheels which passed through an IR LED and photo detector with each cable revolution. Much of the programming historically descended from code designed to work with these sensors and you'll find many GM speed signals to be an even multiple of 2000 pulses per mile.

I have a DRAC with a DIP used for confirming correct jumper settings before modifying a customer's part. It's always nice to know you'll get it right before the soldering gun is applied.


Some have TWO outputs for VSS to the PCM (VSS and TRANS OUTPUT SPEED) and some others I've seen only have one output to PCM/ECM for VSS.

Yes, and that's part of the question I asked. There is no way to generate a correct "trans output speed" signal with only a 4k ppm generator. So that signal will not be present in an older manual trans swap, even though the 94-95 S/T/C/K applications with 7427 family pcm and manual trans appear to have used it along with a "vehicle speed signal." Can you think of any specific applications which did not have the "trans output speed" signal but may have used the later 7427 family pcm?

CDeeZ
08-20-2012, 12:03 PM
Can you think of any specific applications which did not have the "trans output speed" signal but may have used the later 7427 family pcm?

I can't think of any off the top of my head, but there was bound to be some. I know that the DRAC I ended up using APPEARED to only support VSS, but when I added another wire for TRANS OUTPUT SPEED, it worked just great, so it appears that the capability for the two outputs is always there on the DRACs, whether it is used or not...

Blazer3664
12-28-2012, 06:51 AM
Bringing this thread back up with a question.

in the pin out chart on page 1 it lists.................................

C16------E13--------Orange-----------Battery (Inputed in place of Brake Switch for TCC to function)

Why not brake switch?
I had planned to swap in the cruise as well while I am at it. Will this have any negative effects for the cruise?
Kinda thinking this would prevent the PCM from cutting the cruise when I hit the brakes.

Jim

Six_Shooter
12-28-2012, 07:31 AM
Cruise control is a separate system from the EFI.

d21turbo
01-11-2013, 02:44 AM
I converted my 89 chevy astro over to the 16197427 (vehicle was converted to a 350 TBI a few years a go). I was having problems with the knock sensor wiring, originally I connected brown and blue together as desribed in this how to. This does not work on an 89 astro. On this vehicle brown is ground and black is the signal to the ECM (now PCM). This is probably an astro specific thing but there may be other GM TBI vehicles with this discrepency so I suggest going by the pinout of the ESC module which is as follows - pin A is empty, pin B goes to +12 volt, pin C is signal to ECM, pin D is ground and pin E to knock sensor. So connect the wires at pin C and E together. Oh and thanks goes to those who pioneered this conversion and those who have worked to perfect it!

JeepsAndGuns
01-11-2013, 06:02 AM
Just remember the 89 knock sensor is not gonna be the correct one for a 7427, it will need changed.

dave w
01-11-2013, 07:55 AM
I think the knock sensor circuit re-wiring is confusing for a few reasons.

The original re-wiring information from Thridgen.org was for a passenger vehicle. The information on Thridgen.org comments pickups are similar.
(3*)= A.) Wire like 1995 P30 Step Van (http://shop.ebay.com/i.html?_nkw=step+van), ESC Module output to B7
(3*)= B.) Wire like 1995 C10 Truck, Bypass ESC (Blue to Brown) and use Late TBI/TPI 305/350 Knock sensor

The first time I did this conversion was on a 1987 1 ton 2WD dually pickup with a 454, which is at the start of this tread. Not everyone has access to the wiring diagrams for a 1995 P30 Step Van or a 1995 C10 Truck, so this creates confusion on what to do. The GM Pickup used different wire colors for the ESC module (mounted near the TBI) than the passenger vehicle, which creates confusion. Different years of GM pickup production have different wire colors for the ESC module which creates confusion.

If doing this conversion without proper wiring diagrams, I suggest the following procedure with multimeter.

Unplug the ESC module.
With the multimeter set to volts DC turn the ignition switch on, connect the negative lead of the multimeter to the battery negative connection and probe all four pins on the ESC module connector. Only one pin of the four pins will show a near battery voltage, which identifies which of the 4 wires is the ignition power wire.

Turn the ignition switch off, and disconnect the negative cable from the battery.
With the multimeter set to Ohms scale 200K, connect the negative lead of the multimeter to negative battery cable bolt on the engine block and probe the remaining three pins of the ESC module connector. One of the remaining three pins will measure nearly ZERO ohms, which then identifies the ground wire to the ESC Module. One of the remaining three pins will measure nearly 100K Ohms, which then identifies the wire going to the knock sensor.

By process of elimination the 4th pin in the ESC module is the wire that goes to the ECM. The ESC connector wire that goes to the ECM and the ESC connector wire that goes to the knock sensor are then solder spliced together. The ESC ignition power and ground wires can be left inside the ESC Module connector.

I typically use then use the old ESC module ignition power wire and the old ESC ground wire for a heated O2 sensor upgrade.

The last source of confusion is which knock sensor to use. I typically use an aftermarket knock sensor from Standard Ignition part number KS6. I've looked at some of the online aftermarket parts supplier websites; many of the 1993 ~ 1995 GM pickup make / model / year parts catalogs do not show a 4K ohm knock sensor for an automatic transmission only a 100K ohm manual transmission. The Standard Ignition knock sensor part number KS6 is a 4K ohm knock sensor that I have successfully used in the multiple conversion I've done.

dave w

d21turbo
01-11-2013, 01:48 PM
Yes, the multimeter method is the surefire way to figure out the knock sensor wiring. It is also how I ended up figuring it out. I believe that the pin designations on the modules are the same on passenger cars vs. trucks but the wiring colors are different. I could be wrong though, I don't have both to confirm this.

I also used the Standard Motor products KS6 knock sensor. It is working great.

I would have to agree with the people who state this conversion won't make your vehicle run better if you had the original ECM tuned right to start with, but the datalogging is so much better! There is one quirk my van had with the 7747 that has went away now, that I could never get tuned out on the 7747. On cold start at an ambient temp of around 40-50*F I would have to push the accelerator a little bit or it would just flood out with the 7747. If temperatures were colder or warmer than that range it would fire right up with just a turn of the key. Since the change to the 97427 that issue has went away. This could just be an issue with my setup, this engine is far from a stock 350 with more cam than most would consider EFI friendly, and I am sure it could have been tuned out on the 7747 but I couldn't figure it out and the conversion to the 97427 eliminated the need to figure it out. In any case there is definitely something superior about the cold start up routines in the 97427 and it is great having that problem gone after 4 years of dealing with that on daily driving.

Fast355
02-17-2013, 02:10 AM
I would have to agree with the people who state this conversion won't make your vehicle run better if you had the original ECM tuned right to start with, but the datalogging is so much better! There is one quirk my van had with the 7747 that has went away now, that I could never get tuned out on the 7747. On cold start at an ambient temp of around 40-50*F I would have to push the accelerator a little bit or it would just flood out with the 7747. If temperatures were colder or warmer than that range it would fire right up with just a turn of the key. Since the change to the 97427 that issue has went away. This could just be an issue with my setup, this engine is far from a stock 350 with more cam than most would consider EFI friendly, and I am sure it could have been tuned out on the 7747 but I couldn't figure it out and the conversion to the 97427 eliminated the need to figure it out. In any case there is definitely something superior about the cold start up routines in the 97427 and it is great having that problem gone after 4 years of dealing with that on daily driving.

GM loves to switch around the wire colors. I recently swapped my L31 black box to a 0411 in my 97 Express using a guide for a 97 C1500. Found several discrepencies with that swap as well.

The 427 swap was very new when I wrote that guide on TGO, very few had done it and the info was scattered across numerous posts and sites. I swapped my 83 G20 first using a 92 G20 harness, followed by th 87 GMC Jimmy 2.8 and a RS Camaro.

Having done 3 different swap, all on well tuned setups, I have to say the newer 7427 has noticeably better driveability than an earler TBI ECM. They ran smoother, were more responsive, responded to changing conditions better and just all around performed better. The real improvement was E-transmissions however.

I will also add I have a 95 G-series calibration I found with the a/c high pressure switch active and I believe the 95 trucks used them too.

CDeeZ
02-25-2013, 08:40 PM
Chris how did you find this website?!?! That's it, Fast has made his arrival, time to shut the forum down! LOL JK man, glad to have you on here with your EFI-veteran status!



I agree on trying to eliminate the confusion on the knock sensor wiring when upgrading from the 747 ECM to the 7427 PCM, I went through the same thing myself. Blue to brown gives you two grounds on some GM vehicles (which obviously won't work b/c that's only half of the circuit). The multimeter is the only surefire way. It also doesn't help that the wire colors underhood are further obscured by fading/grime accumulation.


Also, I'm not as learned as some of the guys on here, but I have to agree, with what little I know, that the 7427 does indeed have better cold start routines, and also is just better all around in my opinion. Perhaps part of this is the additional resolution on things like fuel tables?

dave w
05-05-2013, 09:12 AM
I think this is a good tread to post a budget update about converting a vehicle with the 1227747 / TH400 combination to a 16197427 PCM which does not have a TH400 Kick Down control.

On vehicles with a 1227747 the TH400 Kick Down Relay is controlled by ECM pin A7 (tan wire with a black stripe), which sends a ground to the Kick Down Relay. The simple budget fix is to install a TH400 Kick Down Switch on the Accelerator Pedal, just like the older non-computer controlled GM Pickups used. The HUGE difference is ECM pin A7 will be switched to ground (black wire with a white stripe) through the Kick Down Switch to make the TH400 Kick Down Relay work. One side of the Accelerator Pedal Mounted Kick Down Switch will be connected to ground and the other terminal of the Accelerator Pedal Mounted Kick Down Switch will be connected to pin A7.

For a long term trouble free service, solder splicing the wiring is HIGHLY RECOMMENDED!

The pictures below are from a 1987 C3500 454 / TH400 that has been updated to a 16197427 PCM that is using an Accelerator Pedal Mounted TH400 Kick Down Switch. The older Accelerator Mounted TH400 Kick Down Switch is a direct bolt in, no modifications required.

dave w

Fast355
05-05-2013, 10:59 AM
I think this is a good tread to post a budget update about converting a vehicle with the 1227747 / TH400 combination to a 16197427 PCM which does not have a TH400 Kick Down control.

On vehicles with a 1227747 the TH400 Kick Down Relay is controlled by ECM pin A7 (tan wire with a black stripe), which sends a ground to the Kick Down Relay. The simple budget fix is to install a TH400 Kick Down Switch on the Accelerator Pedal, just like the older non-computer controlled GM Pickups used. The HUGE difference is ECM pin A7 will be switched to ground (black wire with a white stripe) through the Kick Down Switch to make the TH400 Kick Down Relay work. One side of the Accelerator Pedal Mounted Kick Down Switch will be connected to ground and the other terminal of the Accelerator Pedal Mounted Kick Down Switch will be connected to pin A7.

For a long term trouble free service, solder splicing the wiring is HIGHLY RECOMMENDED!

The pictures below are from a 1987 C3500 454 / TH400 that has been updated to a 16197427 PCM that is using an Accelerator Pedal Mounted TH400 Kick Down Switch. The older Accelerator Mounted TH400 Kick Down Switch is a direct bolt in, no modifications required.

dave w

Dave,

Interesting idea however I am thinking a small patch could be added to control the downshifts similarly to the shift light logic. No extra hardware created.

dave w
05-05-2013, 08:20 PM
Dave,

Interesting idea however I am thinking a small patch could be added to control the downshifts similarly to the shift light logic. No extra hardware created.

I agree, a small patch would be a good option.

dave w

TheApocalyptican
06-21-2013, 12:07 AM
I am planning on switching from the 7747 to the 7427. Need to the get the PCM itself tho, and since I have a V8, do I need a 7427 from a V8, or will the V6 version work too?

dave w
06-21-2013, 05:46 AM
I am planning on switching from the 7747 to the 7427. Need to the get the PCM itself tho, and since I have a V8, do I need a 7427 from a V8, or will the V6 version work too?

I've never tried using a V6 Memcal for a V8 engine. I've done several '7427 conversions, all V8 engines and all had V8 Memcals.

dave w

dumb_dog
12-19-2013, 10:58 PM
For those interested I have both the DRAC and VSSB. These little boxes convert a 40 pulse tone ring into the signal to for the PCM or ECM, and speedo. The VSSB has more outputs than the DRAC. Power, ground, and sensor inputs are the same. The PCM 427 with VSSB uses the RWAL singal (anti-lock brake signal), 40 PPR signal, and 2000 PPM signal. The VSSB also converts the 40 pulse tone ring signal to 2000 PPM for the Speedo. The DRAC is missing the 2000 PPM signal to PCM but because i am using a cable driven speedo i can use the 2000 PPM signal from the DRAC as the signal into the PCM by relocating one wire. With the correct diagrams and much research they can be used interchangebly.

As a side note from another question long ago in this thread the VATS pin is pin B7. There is no wire in that location but it is +5 volts and when pulled low at 30Hz the PCM will allow engine start. So enable VATS and use pin B7. I have tested it and activtly using it in my conversion.

CDeeZ
12-19-2013, 11:46 PM
I'm interested in what you got there bossman. I used both DRAC and VSSB successfully when I was experimenting with them a year or two ago. I've got a pile of about a dozen of them altogether from various trips to the yard.

If memory serves me correct there are two VSS inputs on the VSSB one for VSS and the other for trans output speed? (Been a while since I looked at this so I can't remember exactly).

dumb_dog
12-20-2013, 09:27 AM
You are correct there are two outputs from the VSSB to PCM(s) 6395 or 7427. One is trans output speed at 40 pulses per revolution (PPR) and the other is vehicle speed at 2000 pusles per mile (PPM). The DRAC has the same two signal at different pin locations. So with some repining DRAC and VSSB can be used interchangeably but with the DRAC if you are using an electronic speedo then you will need a VSSB because the DRAC does not have enough outputs for the PCM and speedo. Just FYI the speedo output is at 2000 PPM just like the vehicle speed input to the PCM.

dumb_dog
12-20-2013, 11:25 AM
Hopefully these will help clear things up. Attached are the pinouts for a 1992 DRAC and 1994 VSSB. Also attached is a picture of both DRAC (left) and VSSB (right).

corvetteracing
04-21-2017, 10:21 AM
works & correct