TC lock-up problem

[Professor2]

I have a 94 XLT Ranger, 4.0 with the A4LD trans. I rebuilt the trans about 2 years ago and it worked fine for about 1 year but it kept getting slower to go into gear. I took it to a trans shop and had it rebuilt. Ever since then, I have had trouble with the TC locking up. The TC will lock up for 8 or ten times and then quit. If I reset the codes it will work again about 8 or 10 times. I have taken it back to the trans shop 6 times now and it still does the same thing. They changed the governer, the TC solenoid twice, the torque converter twice and the valve body. I changed the PCM with the same # that is on the one I took out and still the same problem. I checked the codes and can't get anything useful. I get a 111 which is OK and a 538 which is the goose test which is probably my fault. No trans codes. Everytime I want to go somewhere, I have to disconnect the battery and reset the codes. Can anyone tell me what other sensors may effect the TC solenoid and my problem? I would really appreciare any help!

 

[MrShorty]

The most important sensors that the PCM uses when deciding to lock/unlock the TCC are the BOO switch, the TPS, and the VSS. Other sensors will also figure in a little bit.

Before chasing after sensors, though, the next thing I would do would be a quick test to see if it is the PCM not choosing to lock the TCC, or if the transmission is not responding to the PCM's command. Here's basically what this test looks like:

1) Get a wiring diagram and a voltmeter. Locate the TCC solenoid circuit and identify the wires on the diagram and in the truck.
2) Hook your voltmeter up so you are measuring the voltage drop across the solenoid (+ lead to the power supply wire, - lead between the solenoid and the PCM)
3) You might run the output state test (see my notes on pulling EEc-IV codes in the EEC-IV forum) just to make sure you can see the switch from 12 V to 0 V on your voltmeter.
4) Test drive the required number of drive cycles. You should be able to see the PCM command the lockup on your voltmeter. If the TCC stops working because the PCM stops sending the command, then you can further diagnose the EEC side of this to find out why the PCM stops wanting to command lockup. If the PCM sends the command to lockup and the transmission doesn't respond, that indicates a hydraulic/mechanical fault inside the transmission.

 

[Professor2]

Thank you Mr.Shorty for your suggestions. I have a Haynes and a VOM. I don't understand about hooking up the meter and driving to watch the lock-up. The meter leads are only 3 feet long which won't reach from the PCM to where I can watch it.
However, I did change the TPS which was bad. I also changed the BOO, VSS, and the temp sensor for the PCM. Things are better than they were. I can drive longer but it still has the same problem. This Ranger has 246K miles on it so most of the sensors are probably bad. Does the MAP sensor have anything to do with TCC? Could the PCM I replaced the original one with have the same problem?

 

[Kevlar7R]

basically what he was saying is you need to figure out if it is the pcm, or the trans. You may need to use some clip leads to extend the wires.

You need to find out if the pcm is telling the tv, to lockup and it isn't responding, or if it isn't telling it to lock up. That will tell you where to go next.

 

[Professor2]

FIXED TC Lock-up Problem

I checked and found out that the computer was not telling the trans to shift. I couldn't get any codes to tell me what was wrong. I would get a 538 code which is "AC on during test" which didn't tell me anything because I didn't have it on. Anyway, I thought I must have got a bad PCM so I went back and exchanged it for another one. That didn't work any different.
What reallyfixed it was replacing the EDIS Ignition Module. Not only does the TC lock-up but it has a lot more power.
I would like to thank everyone for suggestions and pointing me in the right direction.