1993 Oldsmobile Ninety-Eight. 3800 Series 1. 4T60E. 250,000+ miles.
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 drivability 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, and PCM disconnected. 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.
circuit.jpg
Logic seems to dictate that it must be either the solenoid or its wiring inside the trans. Am I right? A pinched wire, sloppy connection, 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.
I should add that the only time the SES light goes out is briefly and intermittently at highway speeds (~65 mph) and light throttle. 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.
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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