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Discussion Starter · #1 ·
This is the latest evolution of the tranny problem I have been troubleshooting.

I currently have the Malfunction Indicator Light (MIL - aka Service Engine Soon) and the Powertrain Warning Light lit, and DTC's P0750, P0755, P0760, P0765 and P0770.

The DTC's indicate a problem in each of the 5 solenoid circuits.

The Powertrain Warning Light could mean several things, but one of the things it could mean is that the Emergency Operating Program is in effect. And I would say that does correspond with driving behavior: a harsh shift into reverse, and only one forward gear, which could be 3rd -- the designated gear for emergency mode.

I don't think the solenoids themselves are bad. I just replaced A and B, and I don't know why they and the other solenoids would all die at about the same time.

I found and fixed one broken wire and another that was damaged but not broken. As far as I can test, I don't have any current opens or shorts in the wires.

I replaced the PCM with a used one and had it reprogrammed.

My current leading thought concerns voltage. The A5 Pinpoint Test is Check for Battery Voltage. This is measured at the Transaxle Vehicle Harness between each of the 5 solenoid wires and ground. It is measured with the PCM connected, so this is not a short-to-voltage test. There should be some voltage. The test asks "Is there any voltage?" The test does not specify key-on or key-off. With key-off, solenoid A and B would be getting 0 volts, and C, D and E getting 0.75 volts. With key-on, all solenoids would get around 0.75 volts.

But in any case, none of the solenoids is getting more than about 0.75 V. I'm aware that the PCM does not drive the solenoids at 12V, which would kill them, but since I'm getting DTC's for all 5 solenoid circuits, I'm wondering if 0.75 V is enough. Does anyone know what the voltage levels should be running?

The only other questionable indicator I have is from the B Pinpoint Tests, which concern the TFT sensor. B5 is Check PCM and Vehicle Harness for Ground. I believe the test is to locate an improper short to ground in the PCM or vehicle harness. In this test pin 4 tests 0 ohms (bad?) and pin 5 tests 12 Kohms (good). This test is followed up in B6 where you make the same measurements with the PCM disconnected. Here pin 4 and 5 both show infinite ohms (good). The implication is that there is an improper short to ground in the PCM.

I got the same results with both the original and replacement PCM. And with the original PCM out of the car, I did indeed show 0 ohms from PCM pin 91 (which connects to harness pin 4) and PCM unswitched ground pin 103. When I got the replacement PCM, I recall that ohms between those two pins were over 10 Kohms. Then the PCM was installed and reprogrammed. Now I show 0 ohms, as on the original PCM.

Did something in the car circuitry burn a short to ground in this circuit of the PCM? (And here I note that TFT sensor resistance is in the acceptable range, though at the low end of the range. So the sensor itself is not shorted. Nor do I find other shorts to ground or voltage in that circuit.) If so, wouldn't I be getting a DTC related to the PCM or TFT sensor? Could this be responsible for the 5 solenoid circuit DTC's I am getting?
 
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