My E4OD trans is starting out in 2nd or 3rd gear. I ran the TCU self-test and the OCIL & TMIL light just turns 'ON' and stays 'ON'. The OCIL & TMIL light siays 'OFF' when not doing self-test. It's a Diesel TCU.

I have the Overdrive Cancel Switch (OCS) tied to 12 Volts, so OD is always selected.

Does the OCS have to be 'OFF' to run self-test?

What will cause the trans to start in 2nd?

 

Could be the selector switch is commanding 2nd in drive, meaning its like you have the shift lever in the 2nd position. GM transmissions will start in low if put in 2nd and shift up to 2nd. Fords will start in 2nd, if put there.
If its starting in 3rd I think that is the limp mode deal.

 

I replaced the TCU and it is still the same. It starts in 3rd when in Drive. if I select 2nd, then it will start in 2nd. I can start in 2nd, and manually shift into 3rd. It will not upshift or downshift by itself.

When I do the KOEO, the MIL light will come on and stay on. It doesn't flash any codes. I suppose that it's in Limp Mode.

What will cause Limp Mode?

 

Does it actually run self test? I've seen these symptoms before. The problem was the TCM was not getting power. Check for +12V on the red wires, pins 37 and 57 on the TCM connector.

 

OK, it could be a fuse. I looked at the fuses but didn't check them, or check the power.

Is there some different procedure for running the KOEO self-test on these OD transmissions. I just connect Signal Return and STI, then turn on the key. Do you have to operate the OD Cancel Switch.

 

When you connect the wires like you did it will run KOEO. You don't need to press the OD cancel for KOEO, but you do need to hold the accelerator pedal on the floor during the test.

 

I didn't hold the accelerator pedal on the floor. I'll try it Monday. It can't be a problem with the 12 Volts, because the +5 V Ref is there.

There is a delay between Turning the ignition switch 'on' with the STI connected to Signal Return, and the LED illuminating. I think that it is running a self-test, but doesn't complete it. It may time out waiting for the accelerator pedal to be held to the floor.

 

It doesn't wait for the accelerator. It will just set a code.

 

I'll have to look at the transmission connectors. There must be something that it doesn't like.

 

Do you have +12V on the two red wires at the TCM connector? They are pins 37 and 57.

 

I'll check that, but the truck is at the shop. I can't do it until Monday.

I do have a 5V Ref. Do the two 12V wires supply different parts of the TCM?

 

Yes they do.

 

Mark,

I checked the voltage on pins 37 & 57. They are both 12 Volts. I also checked the connections at the trans, and they look OK.

 

Mark,

I was able to read the codes. I get the following codes.

63 TPS below 0.6 volts
67 Neutral Safety Circuit Failure
91 Shift Solenoid 1 Circuit Failure
92 Shift Solenoid 2 Circuit Failure
93 Coast Clutch Solenoid Circuit Failure
94 Converter Clutch Solenoid Circuit Failure
99 Electronic Pressure Control Circuit Failure

I hope that these all have one or two causes in common, like power to the electronics in the trans.

 

Yes they do. It is either a complete loss of power to the trans or a missing ground to the trans. My money is on the power to the trans.