TBI 16168625 to LT1 16188051 Swap No TCC lock up??

[bybyc5]

Been searching for a while here with no luck... All is working really well and runs great, save for NO TCC lock up.

My 1993 K1500/4L60E now has a basically stock LT1 motor now ( 383 with a 4x4 torque cam ), I used a basically stock F-body harness.
I have used a couple different bin files for a 1994 LT1 Automatic, knowing my 93 4L60E is NOT PWM. I have checked and rechecked all my pin/connector locations and all is good as far as I can see. All my Bat+, Key+, and Ground circuits are good.

Some of the stock inputs from the F-body harness I have not hooked up, because, #1 there is no place to use these on my truck AND #2....I don't know what some of them do. :innocent2:

I can while driving ground the TCC lock up wire and I do get TCC lock up. So for some reason the PCM is not commanding lock up?

Inputs/Outputs that are NOT connected: >>>

1- PNP Grounded or not, still no TCC lockup. No PNP in my truck, the neutral safety feature is not electrical. The key wont turn to start if your anywhere other than neutral or Park.

2- EBTCM TP...Not sure what this is or how it works?

What I do have wired up and working.

Brake switch circuit is good.

VSS to and from PCM is good, my speedometer is working perfect. ( I have other questions about this, and getting my cruise control working again....just not as important as TCC Lock up. )

What qualifiers does the 16188051 need to ground pin 11 Tan/BK wire in PCM BLUE connector?

Sure would like the TCC working...:mad1:

Thank you!!

James

[Fast355]

Been searching for a while here with no luck... All is working really well and runs great, save for NO TCC lock up.

My 1993 K1500/4L60E now has a basically stock LT1 motor now ( 383 with a 4x4 torque cam ), I used a basically stock F-body harness.
I have used a couple different bin files for a 1994 LT1 Automatic, knowing my 93 4L60E is NOT PWM. I have checked and rechecked all my pin/connector locations and all is good as far as I can see. All my Bat+, Key+, and Ground circuits are good.

Some of the stock inputs from the F-body harness I have not hooked up, because, #1 there is no place to use these on my truck AND #2....I don't know what some of them do. :innocent2:

I can while driving ground the TCC lock up wire and I do get TCC lock up. So for some reason the PCM is not commanding lock up?

Inputs/Outputs that are NOT connected: >>>

1- PNP Grounded or not, still no TCC lockup. No PNP in my truck, the neutral safety feature is not electrical. The key wont turn to start if your anywhere other than neutral or Park.

2- EBTCM TP...Not sure what this is or how it works?

What I do have wired up and working.

Brake switch circuit is good.

VSS to and from PCM is good, my speedometer is working perfect. ( I have other questions about this, and getting my cruise control working again....just not as important as TCC Lock up. )

What qualifiers does the 16188051 need to ground pin 11 Tan/BK wire in PCM BLUE connector?

Sure would like the TCC working...:mad1:

Thank you!!

James

P.S. Need to edit my sig... No more TPI...dropped an exhaust valve and lunched the block and head...

My guess is the PCM is looking for +12VDC from the cruise control brake switch to some pin to activate lockup. The stock TBI PCMs use the same input to lock the converter. Without 12 volts supplied to the brake switch pin of the PCM the converter will not lock. Took me some time when I retrofitted to my first PCM to find out why the lockup would not command. Worked fine on the 7747, went to the 7427 and no lockup. My guess is you lost 12vdc to the cruise and need it for the PCM.

[bybyc5]

Thank you Fast355,

I will research this out...sounds good as I see on my 8625 pin A-10 wt wire a signal either to or from the cruise control.
Don't see a similar pin in the 8051 pin outs. Hmmmm...gives me a direction to go. I'll search out the LT1 cruise control module function/pin outs and see what I can find.

Do you know if you can piggy back two VSS signals from the one VSS in the transmission?
My stock Cruise Control module and Rear Wheel ABS module needs a signal from the stock speed signal buffer module, and I had to remove the stock VSS connector (which fed this buffer module) from the trans to hook up the LT1 harness for VSS input.

Still curious about the EBTCM TP pin 12 in the RED connector does....My guess is something with traction control, which I don't have and not all F-bodies had it either. My formula does not, but a guy I know that used to have a Z28 did have it, albeit not for long....:innocent:

Worse case scenario is I set up either the canister purge circuit or the egr circuit to ground the TCC pin. Really would rather it be correct though.
Either that or I will have to piggy back the two pcm's...not desirable.

Thank you!

James

[Fast355]

Thank you Fast355,

I will research this out...sounds good as I see on my 8625 pin A-10 wt wire a signal either to or from the cruise control.
Don't see a similar pin in the 8051 pin outs. Hmmmm...gives me a direction to go. I'll search out the LT1 cruise control module function/pin outs and see what I can find.

Do you know if you can piggy back two VSS signals from the one VSS in the transmission?
My stock Cruise Control module and Rear Wheel ABS module needs a signal from the stock speed signal buffer module, and I had to remove the stock VSS connector (which fed this buffer module) from the trans to hook up the LT1 harness for VSS input.

Still curious about the EBTCM TP pin 12 in the RED connector does....My guess is something with traction control, which I don't have and not all F-bodies had it either. My formula does not, but a guy I know that used to have a Z28 did have it, albeit not for long....:innocent:

Worse case scenario is I set up either the canister purge circuit or the egr circuit to ground the TCC pin. Really would rather it be correct though.
Either that or I will have to piggy back the two pcm's...not desirable.

Thank you!

James

You should be able to bypass the VSSB aka dRAC and use the speed signal output from the LT1 PCM to feed your RWABS and the Cruise. The LT1 cars and Vortec trucks use the PCM the same way that older vehicles used the VSSB or DRAC. If not you can piggyback the signals but the polarities have to match. If you piggy back and suddenly lose a speed signal, swap the wires at one of the modules. When I was running OD Maf with a 4L60E I had to do the same thing with the TBI PCM. The white wire from the PCM to the Cruise just tells the PCM the cruise is enabled which turns on the cruise control shift tables.

[buddrow]

This is from 97 LT1 Camaro cruise control.

[buddrow]

This is from a 95 1500.

[bybyc5]

You should be able to bypass the VSSB aka dRAC and use the speed signal output from the LT1 PCM to feed your RWABS and the Cruise. The LT1 cars and Vortec trucks use the PCM the same way that older vehicles used the VSSB or DRAC. If not you can piggyback the signals but the polarities have to match. If you piggy back and suddenly lose a speed signal, swap the wires at one of the modules. When I was running OD Maf with a 4L60E I had to do the same thing with the TBI PCM. The white wire from the PCM to the Cruise just tells the PCM the cruise is enabled which turns on the cruise control shift tables.

That's good to know.
Thank you!

Now have some circuit checking to do...

Thanks again,

James

[bybyc5]

This is from a 95 1500.

Thank you for the diagram's. This will help me identify the circuits I need to deal with!

I hope I don't let the smoke out of one of these modules.

Thank you,

James

[buddrow]

Hope it helps. gimme a few and I'll see about posting the actual circuit requirements. This is transplanting into the 95ish 1500 correct?

[buddrow]

See if this gets you where you need to be as far as the multi-function and brake switch operation affects the cruise module on the 95.

[buddrow]

Also, if you have the CHMSL, check the bulb, if the bulb is blown it can affect cruise operation.

[bybyc5]

Hope it helps. gimme a few and I'll see about posting the actual circuit requirements. This is transplanting into the 95ish 1500 correct?

Thank you for the added info.
It's a 93 K1500 and yes it's an LT1 transplant. 16168625 is the old PCM, and 16188051 is the LT1 PCM, using 1994 LT1 bins because my 1993 4L60E is NOT a pulse width modulated TCC lock up, it's either on or off...And right now mine is always off....:doh:

I do see a possibility for me to try. Thanks to the schematics you provided and the info from Fast355. Looks like the 16168625 PCM uses a boo ( brake on/off ) signal to disengage the TCC, and the 16188051 looks FOR a Key + signal on the TCC pin to signal the PCM for lock up...unless I looked at it wrong...having winows 10 issues today and am cross eyed from tech their support...:mad1:

I really appreciate all the input guys.. next round of carbonated beverages are on me !! :happy:

[buddrow]

Here is the schematic for the 93. Operation should be the same as should the wiring, but in 95 they did change some things so I would use the 93 diagram to be positive. My apologies if the comments are blurry, I have no control over that part since the pic is from GM factory manual and it's not a high resolution pic.

Bud

[bybyc5]

Got to tip my hat and say THANK YOU!! :jfj:

Got it all working as designed. TCC locking up correctly, and all other modules receiving VSS inputs.
I piggy backed the VSS at the Trans Tail shaft, of coarse got it backwards first try...but swapping the polarity worked!

And looking at the schematics you gave me ( Thank you :thumbsup:) I wired a normally closed relay to keep Key+ power applied to the BOO circuit, opening the circuit when the brake pedal is applied...works perfect!

Who'd a thunk stepping on the brake pedal interrupts power to the PCM...

I appreciate all the effort you guys gave me!! :rockon:

Thank You,

James

[buddrow]

Good deal! Glad we could be of assistance.

Bud

[lionelhutz]

You're interrupting power to the PCM brake switch input? Light blue/black wire on pin C14. When I did my LT1 transplant I just put power to that wire. Works fine unless you're stepping on the brake while holding the throttle since the PCM is programmed to unlock the TCC at 0% TPS.

I believe A12 is a PWM output to the EBTCM to tell it what torque or throttle percentage or something similar that the engine is producing. Pin A23 is a PWM signal back to tell the PCM how much to reduce the engine torque, by retarding the timing.

[bybyc5]

You're interrupting power to the PCM brake switch input? Light blue/black wire on pin C14. When I did my LT1 transplant I just put power to that wire. Works fine unless you're stepping on the brake while holding the throttle since the PCM is programmed to unlock the TCC at 0% TPS.

I did consider doing just that, leave a 12V direct input, but considering the pin is labeled brake switch signal, I figured the 12V signal it monitored needed to know when the brake pedal was depressed. Maybe during braking at speeds where the TCC in locked up, it is desirable to disengage the TCC? And mine does. If you touch the brake pedal on a steady cruise, that tachometer jumps up a 100 rpm or so, then re-engages when released.

Not sure what the designers intentions were. No, I don't power brake this vehicle....have many others though !! :thumbsup:


I believe A12 is a PWM output to the EBTCM to tell it what torque or throttle percentage or something similar that the engine is producing. Pin A23 is a PWM signal back to tell the PCM how much to reduce the engine torque, by retarding the timing.

Yes, this circuit has eluded me, however the little research I did led me to believe it was for the Traction Control Management ?? I know some F-bodies had them, mine ( My formula ) did not being an M6.

I have also removed this from some Z-28's that did have the TCM. Not sure about any of the EBTCM circuit? But it appears to have no adverse effect on my truck without it.
This LT1 swap into my truck was a major improvement drive-ability wise. My OE system was map based, and no MAT input. So the old 383 ran very well with some tweaking of the 16168625, with great mileage. Was going to go from $E6 to $OD and add the MAT circuit....But had a valve spring collapse and dropped an exhaust valve that ended that motor.

So I had a spare LT1 motor "in stock" and rebuilt it a 383 with a 4x4 low rpm torque cam. Very happy with the result.

So now I may be adding a lot of stuff to the for sale section to clear my shelf of several $E6 and $OD PCMs and all the TBI and TPI engine components accumulated over the past years. Complete TPI and TBI manifolds and engine brackets, etc.....Even have an LT1 intake manifold I drilled a hole in it to mount a distributor and run the LT1 initially with my $E6 PCM. But now it's 100% LT1. Opti and all.

Thank you all for the help!!

James

[lionelhutz]

I've driven my car for a few years and haven't noticed any bad effects with the input simply connected to power.

There is a traction control spark table. You can zero it out so the EBTCM input (A23) can't do anything.

[Fast355]

I've driven my car for a few years and haven't noticed any bad effects with the input simply connected to power.

There is a traction control spark table. You can zero it out so the EBTCM input (A23) can't do anything.

Not sure which brake switch setup his truck had from the factory as GM switched to a single brake switch on the newer models, but both setups have a 12V output that is switched off when the brake is activated. His factory TBI setup had the same input that could have been used without a relay. Even my old 1983 G20 van that came with electronic/vacuum cruise had a cruise control brake switch that doubled as a vacuum release valve that had the correct output to feed the PCM.

[bybyc5]

Not sure which brake switch setup his truck had from the factory as GM switched to a single brake switch on the newer models, but both setups have a 12V output that is switched off when the brake is activated. His factory TBI setup had the same input that could have been used without a relay. Even my old 1983 G20 van that came with electronic/vacuum cruise had a cruise control brake switch that doubled as a vacuum release valve that had the correct output to feed the PCM.

That's good to know. I didn't see that feed. I did tap the feed that fed the brake lamp circuit.
Thanks again.

James