GM Quad Driver Chart C3 and P4

[1project2many]

From time to time discussion turns to using code and ecm that were not originally put together. A common example might be putting $58 into a 7730. This chart is from an old GM training manual and could be used to help identify where to connect pins for outputs when trying to migrate code between ecm's or just to help diagnose a problem with a Quad Driver Module.

[kevinvinv]

Hey 1Project,

I am getting QDM failures posted both by my scan tool as well as TunerPro RT.

What is weird is that it doesn't show up as a trouble code... just as a line item saying "quad driver module failure" YES.

Any idea how a person should go about debugging this?

[1project2many]

What kind of scan tool? This is probably a flag in the data stream... need to look at the ALDL definition to know. Is anything not working? QDM's control outputs.

[kevinvinv]

Both my MPSI scanner (old) and Tuner Pro both show QDM Fault A/B= Yes. This does not show up as a trouble code on either device... just in the data stream (bit mask in tuner pro) they show up.

Tranny is acting super wacky in my opinion- not downshifting right when I want to engine-brake. Before I dig further into that I want to find out if the QDM thing is real or not.

OK- I'll try to find the ALDL definition (is this where the stream is defined?) and see what I can figure out.

[kevinvinv]

A bit of searching and can't find a definition for the ALDL data stream. Should I be finding that somewhere? I assume that data is used to create things like the adx file. I wouldn't mind seeing what is all in the stream if it is available.

Also was searching for a 6395 schematic... with no luck. Any pointers on finding these two items?

Thanks man.

[billygraves]

..............

[kevinvinv]

Billy, wow... would love to chat about those days in GM!! I got the MPSI about 15 years ago on a closeout from an injector place. Yep- the back of it says Sterling Heights MI!

I stayed the night in the Corvette plant back in 91 or so during the GM Sunrayce... those were the days!! Bob Stempel...

So what you are saying is that the scanner might not be providing good info on this... right? My PCM is 16196395/16197427 . If I could find out that these "fails" are false- it would be great ... but I am experiencing some transmission problems so I am suspicious about these things.

I wish I could get my hands on a schematic for the PCM... so far havent been able to find one yet.

Thanks!!!!

[1project2many]

1Project,
When I was @ GM in 94, I asked the Powertrain Group Software personal about these quad drivers. The diag codes will only function IF the actual quad driver has a software output to the internals telling of a failure. This was in 94-95. I inquired about this to include this in the OBD-2 diagnostic codes we were developing. If the Controller has the Good or $$$ drivers, they have diags and an output for this, the less $$$ don't. That's what I remember anyway.
That matches what I remember from STG and the training centers. The software may be there but the hardware isn't always compliant. The scantool won't report a code if the hardware doesn't support it. After I llearned more about the code I associated that phrase with the codes actually being enabled.



You are looking at MPSI??? That was in Sterling Heights MI. Anyway. When I was the Tech-1 Powertrain person at GM in 90-94 the ECM's sometimes had good info with these quad drivers. Sometimes not so good. I have NO IDEA what ECM or vehicle you have, but some ECM's I could NOT use the QUAD driver info. Some was because one of the 4 Quad driver pins were not used in a certain car/truck line.

7427 PCM? My thought was to check data stream definition for the particular mask. Seems to me that if trouble codes are not reported that confirms the hardware can't be trusted.

Kevin... there are original text files around that contain the datastream definitions. Not sure where to find them anymore but the extension was .adl and they used to be in a big zip file. I have a copy at home that I can upload if someone doesn't post a link. 6395 is a C3 (no QDM codes). Find the mirror of Ludis' page and see what's there.

[billygraves]

............

[kevinvinv]

Hey 1Project... can you just clarify what you mean by this statement: 6395 is a C3 (no QDM codes). ?

Thanks!

[kevinvinv]

Thanks for this info BillyGraves! Thanks!!!

[kevinvinv]

I found out what C3 means from Ludis' site-- He states that 6395 is not C3 though as far as I can tell (here-> http://www.exatorq.com/ludis_obd1/p4xref.html )

Anyhow- still cant find a schematic :( --

I basically need to figure out if this quad driver thing has ANY validity b/c if those errors are false.. then my tranny is shot and I gotta take it out and send it back to Chicago ... so that is why I am obsessed with this quad driver stuff at the moment!! :) THanks all!! Sounds like it would be easiest for me to find someone with a tech 1...

[1project2many]

If a data stream has a bit status for a Fault in a particular QUAD driver, it could STILL BE INCORRECT. Only the Tech-1 is correct with the QUAD drivers IF they were displayed on the T-1 Screen.

Understood. I was looking for fault code presence in datastream. Fault code should not set when status could be incorrectly reported. If fault code is not included in data stream then the assumption is active status bit cannot be trusted. If fault code is reported then we cannot discount status bit.

I dug out audio recorder at a dealership and people laughed. I'd let car owner borrow recorder then bring it back after problem occurs. Saved me from driving for free.


I basically need to figure out if this quad driver thing has ANY validity b/c if those errors are false.. then my tranny is shot and I gotta take it out and send it back to Chicago
Sorry about confusion on ECM/PCM type. Was thinking that number was same as manual trans equipped truck which had C3. I believe the 6395 PCM you have was replaced by the 7427. But diagnosing trans doesn't require digging through data or viewing QDM info. If the problem is slipping you'll likely have burnt/bad fluid to accompany. If the problem is electrical you can check voltage / resistance on solenoid control lines to confirm pcm is controlling properly. What is symptom? Do you have Factory Service Manual to assist with diagnosis?

[kevinvinv]

Thanks 1Project,

The problem is this:

Drive in 4th at 50MPH
Let off gas,
Truck engine brakes a little
manual shift into D3
Truck seems to go into neutral (less engine braking - still going about 50)
manual Shift into 2nd,
Can rev gas a little bit and it is like it is in neutral
Rev up to 2500 and boom... trans shifts into 2nd.
If I don't do this Revving routine, it will NEVER shift to second... will seem to coast in "neutral" ALL the way down to stop

That's my frustrating problem! :)

I have a video of this as well as a TunerPro trace if anyone is really interested :)

Need to know if it is somehow electrical or chip related or if this tranny has to come out (again).

[billygraves]

.............

[1project2many]

Well, it sounds like a very common 700R4 problem. It sounds like the trans is shifting out of 2nd but you have a mechanical problem. The trans will default to 3rd gear if the shift solenoids have no power so the problem likely isn't electrical. The Sun shell splines maybe? Try manual upshifts and see if you find an unexpected neutral where third should occur.

[1project2many]

So when you see these in these AFTERMARKET SCAN TOOLS, they NEVER verify each engine/trans selected. They just put it all in just in case. They don't have the resorces and knowledge of the OEM and why.
These Mode Words in the Data stream are sometimes refered to as a bit packed word (of 8 bits).

I've talked with some s/w guys on the aftermarket scantool end. They license a datastream and get a definition, then make sure the scantool can display what the definition shows. That's it. If the datastream def. info says the engine is a 3200 hp turbine and the trans is a 125 then that's what they believe. Hacks, internet info, and other guys' scantool info are all off limits since it wasn't acquired through agreement. One guy had personal version of commercial scantool that would plug into edge card connector of C3 like Dynamic EFI's Lockers for scantool data, but could not share software at all.

The definition files I'm talking about were directly from GM. Not sure what was used to built the Tuner-pro definition files.

[kevinvinv]

Well, it sounds like a very common 700R4 problem. It sounds like the trans is shifting out of 2nd but you have a mechanical problem. The trans will default to 3rd gear if the shift solenoids have no power so the problem likely isn't electrical. The Sun shell splines maybe? Try manual upshifts and see if you find an unexpected neutral where third should occur.



Both my builder (in chicago) and a local shop think that the overrun clutch drum is bad. Not sure how this could happen with only a 1000 low stress miles on this thing. Oh well.

Can I get one clarification though? When people say "manual upshift" for example... what is meant by that? If I shift up via the lever does the PCM still do something? I guess I don't really understand how the lever and the PCM work toghether... I actually wonder why the lever even goes to the tranny at all if the PCM can handle the shifts through solenoids etc...

[RobertISaar]

I actually wonder why the lever even goes to the tranny at all if the PCM can handle the shifts through solenoids etc...

there are still a lot of traditional parts still in newer(but not necessary all newer) transmissions....

parking pawl is entirely cable operated
reverse may use the shift solenoid combo for 1st gear(though IIRC, it won't matter, it is just for anticiption of getting out of reverse and into a forward gear), but the manual shaft needs to be in the R position to send pressure where it needs to be to engage reverse instead of 1st.
the manual shaft can do some interesting things depending on the transmission.... for instance on the 4T60E(and 4T65 derived from it), if you disconnect the circuits of the shift solenoids, putting the shifter into reverse will still allow reverse, putting the shifter into 1 or 2 will cause 2nd gear, putting the shifter into 3 or 4(or D/OD) will cause 3rd gear. all of these are because of how the manual shaft(which is directly controlled by the shifter cable and therefore, shifter) causes certain things to happen in the transmission.
actual line pressure can also be significantly effected by shifter position. what could normally be ~65PSI idling in gear, pulling the shifter down into 1st may bump it up to the 200PSI range.

[1project2many]

Not sure how this could happen with only a 1000 low stress miles on this thing.

Because it's a 4L60E!

I'll admit that I have a very strong negative bias. It's because I was around when Chevrolet first released the 700R4 on us poor technicians. It's taken GM and the aftermarket over 30 years to get this transmission "fixed" but getting a good trans overhaul can still require a lot of hard part changes and $$. I've got the same trans in my Suburban and when it fails again I'm hoping to swap to the 80E. It's not a cheap or simple changeover but I'd estimate it's 90% effective as a fix in stock and mild applications.


Can I get one clarification though? When people say "manual upshift" for example... what is meant by that? If I shift up via the lever does the PCM still do something? I guess I don't really understand how the lever and the PCM work toghether... I actually wonder why the lever even goes to the tranny at all if the PCM can handle the shifts through solenoids etc...

Manually selecting a gear is an indication that conditions are not typical so additional/different functions are enabled. In the 4L60E engaging 1,2,or three supplies pressure to the overrun clutch to provide engine braking. In OD when driveline speed is greater than engine speed the engine automatically "disconnects" from the gears. The manual position also provides a mechanical limit to shifts. As to the question of why, the transmission began life as a fully mechanical transmission but was modified to remove most of the electronic controls. Sometimes change is slow to happen, and as described by billygraves, oftentimes left over functions or items not required to be changed are ignored. Newer transmissions have greatly reduced functions through the manual shaft as they are being designed primarily for electronic control.

[twiztidditzwit]

.............

sure would’ve been nice to see what he said… 😡