Computer wiring diagram

Okay, that twelve volts should also be found on the red wire, terminal four, at the solenoid pack. There are three pressure switches in the solenoid pack, but I have never worked on that part of the system. I cannot find a written description, so I am going to have to guess that twelve volts gets switched onto those three lines you are looking at when the appropriate switch turns on. If that is correct, we know all three switches will not fail at the same time. One failed switch would be detected as such, and an appropriate fault code would be set.

It is also possible the computer sends out twelve volts on all three of those lines, then the switches ground that and send the voltage on its line to zero volts when it turns on. There is no ground wire in the connector for the solenoid pack, but that circuit could be made through the mounting bolts. Regardless, it is again not likely all three circuits would develop a problem at the same time.

The first thing to do is have the diagnostic fault codes read and recorded in the transmission computer. That will indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. You are doing tests that are the last step in the procedure after you know which circuit to look at.

A lot of auto parts stores rent or borrow tools. See if one of them has a scanner that will access the Transmission Computer so you can read the fault codes. When the system goes to limp mode, the transmission relay is turned off, so you will be missing those voltages at the solenoid pack. You're trying to diagnose the clue, not the cause of the problem.

A good suspect at the mileage you listed is slippage in one of the clutch packs. The fault code will refer to "gear ratio error". The additional observation is it goes to limp mode during or right after a shift, usually an up-shift. If you identify that it always occurs when going from second to third, for example, accelerate a little harder to delay that shift, then let off the gas so the shift occurs with little torque on the transmission. If clutch plate slippage is the cause of the problem, doing that will give the overdrive clutch packs time to lock up before power is reapplied.

The scanner will also let you see the "clutch volume index", (CVI). That is a set of four numbers corresponding to the number of CCs of fluid it takes to apply each of the clutch packs. An experienced transmission specialist can tell how much life is left in each of them. Slippage occurs when the number for a clutch pack can't update any more, meaning no amount of additional fluid will be enough to fully apply it.

It sounds like the transmission has an internal failure and needs to come apart to fix it.

The only way I know of is to whats the input and output readings on a pro scanner or you can send it into a re-builder they can run tests to see as well.

To me it sounds like the transmission need to be rebuilt. Limp mode would happen when the internal seals would leak.

Good to hear, please use 2CarPros anytime we are here to help.

Cheers, Ken

Main ECM connector. I don't think it has a name that I know of. Caradiodoc might chime in with it