[4T60E] Quad Driver Module B Fault (PWM TCC) After Shoddy Rebuild

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#1
Make
Oldsmobile
Model
Ninety Eight
Year
1993
Miles
255,000
Engine
3800 Series 1
Backstory: Had the car for nearly 15 years and over 100k miles. Have done all the repairs myself except the recent transmission rebuild. The trans shop, who barely speaky the Inglés, did a real craptacular job. Lots of broken and missing odds and ends -- even unrelated to the trans -- after the two-month long rebuild.

So I finally get it back... and the Service Engine Soon light is on. Reluctant to "take advantage" of the warranty and see how much longer they can keep my car and what other trim pieces they can break and screws they can lose, I decide to fix it myself (if possible).

Pulled the codes: 31 and 56. PRNDL switch and quad driver B. I was able to easily readjust the PRNDL switch and I think that code will be gone ( I just did it a few minutes ago -- car starts in neutral now where it didn't before.)

So that leaves Quad Driver B.... But first...

Massive driveability and shifting issues since I got the car back. I did discover a short piece of clear plastic tubing plugged into the vacuum modulator that had collapsed in on itself. New vacuum hose will be arriving tomorrow. So that should fix some of the issues, which are:

- Slipping 2nd, 3rd, and OD... almost like being in neutral unless I give it some heavy throttle, then harsh engagement.

- Erratic shift points. Will upshift and downshift both too late or too soon. I think he put different-sized gears in compared to what I had, and compared to what my PROM is programmed for. Very annoying.

So basically ill-timed shift points, up and down, which vary trip to trip... and feeling like it's in neutral half the time.
Also there's a nice big trans fluid leak which I haven't pinpointed yet, but I do keep the fluid topped up. Seems like it's coming from the pan underneath but I need to jack it up and crawl under there and look around with the engine running (that's when it leaks).

Back to DTC 56 and Quad Driver B. I have the factory service manual and did some probing around. The diagnostic had me measure the current through the wires on that circuit (EGR, TCC, PWM TCC) with key ON. All were in spec except PWM TCC solenoid which had no current, indicating that it's open I assume. I checked that wire's continuity between the PCM and the transmission harness and it's good.

Logic seems to dictate that it must be either the solenoid or its wiring inside the trans. Am I right? A pinched wire, sloppy connections, a broken pin on a harness, or just a bad solenoid... All of those are plausible given what I now know about the quality of the rebuilder's work.

So do I have to pop off the side case now (big job which I dread), or is there some other avenue of investigation I'm missing?

Thanks in advance fellas.
 
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#2
I should add that the only time the SES light goes out is briefly and intermittently at highway speeds (~65 mph) and light throttle. But it will fairly consistently go out for a minute or two at a time at steady speed/throttle over 60mph.
My guess is that this is the only time when things "look right" to the PCM, when it would be grounding the PWM TCC solenoid anyway, turning it on.
But I might be totally wrong about that.

All other times the SES light, meaning the fault, is persistent and unwavering.
 

bp042665

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#3
first off after you fix the vacuum line the shift quality should improve the vacuum controls most of that and the pwm solenoid is a pulse with modulating solenoid the computer controls the ground the power is all the same feed for solenoids tcc shift a & shift b so if you power up all the solenoids and ground each 1 and hear a clicking noise every time you ground it then most likely you have a bad computer but if you don't hear a click on the tcc solenoid you either have a bad solenoid or internal wire or connector problem I added this I hope it helps
 

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#4
circuit.png

Thanks for your input. I don't think it's the computer, at least for this particular issue, because the problem begins before it reaches the PCM.
Like you said, the solenoids are all fed from the same power source before making their way to be grounded by the PCM; and I know "1350 DK BLU" has continuity from the transaxle connector to the PCM.

So unless I'm missing something, it seems like the circuit open has to be internal in the trans.
 

grcauto

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#5
Thanks for your input. I don't think it's the computer, at least for this particular issue, because the problem begins before it reaches the PCM.

Your not thinking this through. The continuity of the harness from the trans to pcm is good but that does not mean the pcm is actually grounding the solenoid.

Like you said, the solenoids are all fed from the same power source before making their way to be grounded by the PCM; and I know "1350 DK BLU" has continuity from the transaxle connector to the PCM.

So unless I'm missing something, it seems like the circuit open has to be internal in the trans.
That's true but the open may be the pcm itself. The drivers are nothing but a transistor that is turned on and off creating the pwm signal. These fail often and it'll be the same as an open. You can monitor this with a good scan tool.
 
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#6
The diagnostic procedure in the FSM has you test the circuit with the PCM disconnected. We're testing the circuit before it gets to the PCM.
In other words, the PCM can't ground (or fail to ground) a current that never even reaches it.
I probed the PCM harness after it was unplugged from the PCM. Positive test lead to each specified pin, negative test lead to ground.
Only the PWM TCC circuit had an apparent open.
 
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#7
could the EGR you mention be the cause of the quad driver issue?

There is 12v from trans to PCM, you claim PCM is not grounding solenoid, it (PCM) would NOT command TCC KOEO.
What else is on quad driver as that components circuit could be cause of failure of entire quad driver and all components on driver B.
 

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billr

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#8
I didn't study all the words above, but are you saying there is no continuity between the trans pin B and pin E, with the harness disconnected? And there is about 20 ohms for all the other solenoid pins to E? Yes, that means there is a problem inside the trans; either the solenoid coil or its connection to the (12V) bus-plate inside.
 
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#9
I didn't study all the words above, but are you saying there is no continuity between the trans pin B and pin E, with the harness disconnected?
Well, that's what we can deduce, yes. Although I did try that specific test, and it did show no continuity (which is what is to be expected based on the other tests), I sort of ruled it inconclusive because of the difficulty in getting test leads or even alligator clips to stay on those little pins in that cramped space without really being able to see down in there. I did try repeatedly and each time showed no continuity between the two pins.

And there is about 20 ohms for all the other solenoid pins to E?
This we can also deduce since I measured roughly .6A at 12V coming from the other solenoids at the PCM harness.
.6A X 20Ω = 12V

I should have been able to measure ~1A on "1350 DK BLU", but got nothing.

Yes, that means there is a problem inside the trans; either the solenoid coil or its connection to the (12V) bus-plate inside.
It's looking that way. I just want to make absolutely sure before I dedicate so much time and energy into disassembling a good chunk of my car for one little effing wire.
 

grcauto

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#10
The diagnostic procedure in the FSM has you test the circuit with the PCM disconnected. We're testing the circuit before it gets to the PCM.
In other words, the PCM can't ground (or fail to ground) a current that never even reaches it.

There is no current in the circuit UNTIL the driver in the ECM grounds it. At that time current flows.

I probed the PCM harness after it was unplugged from the PCM. Positive test lead to each specified pin, negative test lead to ground.
Only the PWM TCC circuit had an apparent open.
So with the ECM disconnected you have an open in the wiring from the trans to the ECM? Is that correct? If so, you found the problem.
Also you say that you have .4 - .7 amps on both shift circuits and 0 amps on the TCC. How are you measuring these?
 
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#11
There is no current in the circuit UNTIL the driver in the ECM grounds it. At that time current flows.


Or until my multimeter grounds the circuit, which is what the FSM had me do (the results of which having ruled out the PCM as the problem).

So with the ECM disconnected you have an open in the wiring from the trans to the ECM? Is that correct? If so, you found the problem.
There's continuity between the PCM and the outer trans harness. Continuity is lost inside the trans between pin E (switched 12V+) and pin B (PWM TCC ground)

Yeah. Seems like I solved my own problem. But I figured I would ask the pros if there is anything else I can check. Or any other tips or tricks I could employ to solve this.
 
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#12
Also you say that you have .4 - .7 amps on both shift circuits and 0 amps on the TCC. How are you measuring these?
Disconnected PCM and set aside. Key "ON". Probed specified pins in wiring harness with positive test lead. Negative test lead to chassis ground.
 

billr

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#13
The fact that only the one solenoid doesn't check out, the others are OK, kind of proves your test procedure is OK. You gotta go in deeper. My wonderment would be if doing some air-checks on the clutches/seals would be warranted, once you are in checking for the solenoid/wiring. I don't know how much extra effort the air-checks would be. The only reason I'm considering going beyond that one solenoid is because you think this re-build was done so poorly.
 
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#15
The only reason I'm considering going beyond that one solenoid is because you think this re-build was done so poorly.
I think this says it all, and it's but one of many examples I've found outside the trans. Who knows what's going on inside.
[This is the transaxle connector]
moronic_slop.jpg

The fact that only the three wires to the solenoids were stripped so... well that tells something anyway -- like maybe they knew there was an issue after the so-called rebuild. And yet they still gave me the car back with this issue.

Another example of their utterly incompetent workmanship is, for example, when I got the car back, the hood wouldn't pop. I spent a couple hours figuring out that not only was the under-dash hood release out of its bracket, but the hood pop-up spring was just flat out gone. Either gross negligence or they simply stole it. Also, the PCM was just tossed back up under the dash. No mounting hardware. Who knows where that went or how it was even oriented before. Lots of missing screws in various places. Even one of my steering wheel radio/AC controls was missing. They just didn't give a crap about anything.

The offender: download (1).jpg

The fact that only the one solenoid doesn't check out, the others are OK, kind of proves your test procedure is OK. You gotta go in deeper. My wonderment would be if doing some air-checks on the clutches/seals would be warranted, once you are in checking for the solenoid/wiring. I don't know how much extra effort the air-checks would be.
The most I've ever done to a trans is replace the mount and fluid cooling line to the radiator. Needless to say, removing the transaxle side cover seems pretty daunting. As for air checks... I have no idea what they are much less how to do them. But, I'm all ears if you want to elaborate.
 
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