Torque converter lockup problem

[johnson350]

Ok well today I went under the hood and hooked the manifold vacuum sensor to a full vacuum source. No code, but still no converter lockup.

If it does use a TPS reading, that could be why because it was changed.

Olds307 and 403, I turned up the idle a bit and the light no longer comes on.

Bonnewagon, I guess I'm going to have to run a manual switch to it. Hopefully My transmission isn't messed up!

 

[Bonnewagon]

Before you cut any wires why not trace them back and see if any of the other components are at fault. If they all check out then by all means jump it and test the trans itself. Or you could actually pull the connector on the side of the trans and wire a simple 12 volt bulb in place of the lockup circuit and carry that inside the car. Then take it for a ride and if the bulb lights then you know the computer is giving the command and the system is functioning. But then that would point to the trans. Luckily the solenoid and high gear switch are easily serviced after dropping the pan. You needed to change the filter anyway, right?

 

[jrm81bu]

I know on the tbi systems you can actually run a jumper between to of the pins in the aldl connector to lock the convertor. Not sure which ones off hand and i'm not sure if that would still work on the ccc system, but if it does, that's an easy way to check.

 

[Bonnewagon]

King_V that's the problem with GM. Although the systems are basically the same, each division put their own twist on things. So what Buick did may not be how Oldsmobile did it and Chevy did it another way etc, etc. Without the specific factory manual it's difficult to verify exactly what his system consists of. But it is easy to eliminate possibilities and separate the electrical system from the trans itself and test.

 

[johnson350]

Ok, I am almost absolutely sure the transmission works fine. This morning on my drive to work the converter finally locked. It locked right at 40 mph. I pulled off and ran it through the gears again and same, it locked at around 40 mph.

So here's the twist - I'm driving home this afternon, no lockup again .

What changed between this morning and this afternoon??

I did absolutely nothing under the hood. Bonnewagon, I never cut the wires going to the transmission (which I really didn't want to do). I'll check it if I really have to for 12 volts coming from the computer with my meter. I also changed the fluid and filter maybe 1000 miles ago so it's in pretty good shape.

jrm81bu, I am looking at a diagram right now of an ALDL port for a ccc car. There is a TCC terminal on terminal F. Would all I have to do is run a jumper wire from the ground terminal to the TCC terminal in the ALDL connector and it should lock up?

 

[King_V]

I didn't think of this before, but I do know that GM also had a temperature threshold.

Is your thermostat working correctly, and coolant temp sensor sending the correct value to the ECM? I belive below 150 degrees or so, the computer will not lock the torque converter.

I'm trying to recall from very hazy memory, though, so take this with a grain of salt. Maybe your temps were lower on the way home than they were on the way to work, say, if you were in traffic going to work, but not in traffic when going home? Just taking some guesses here.

 

[johnson350]

King_V, yes it is all working properly and I just installed a new water pump and radiator. I also only drive about 7 or 8 miles one way to work, so it doesn't run for long. I bet it was warming up quick though without the lockup. I did not know that the ECM used temperature readings, but I'll keep that in mind if anything else ever goes wrong.

It's working again. I hooked a jumper wire and a switch to the ALDL for the TCC ground. It works well, It shifted to third, I flipped the switch and it locked up. Then it started doing it on its own again, overiding the switch. So, no idea why it wasn't working before, but it works now.

Thanks everybody who helped me with this problem! 😀

 

[Bonnewagon]

Well there ya go! I'm glad you sorted it out. Perhaps the computer had a brain fart or the solenoid was stuck open. At least if it acts up again you know it's in working order and you would be looking for an intermittent cause.