ADL

Truck drives fine in 2wd, Service 4wd light is on, no lights on switch are on, does not shift to 4wd. C0309 code set. Any suggestions what the problem is?

Thanks for any help.

ToooTall1

As stated in earlier threads I would start with the grounding wires under drivers door, outside frame looking forward. Clean to bare metal both connectors and frame, then check and clean T/C , forward axle and dash switches connector. Will try to find what the code is and reply later.

ADL

Checked / cleaned ground wires and connections at TC. No change.

Thanks for any help.

ToooTall1

DTC C0309 refers to T/C motor A/B Circuit High. What is happening is the ATC Control module senses a high voltage on circuits 1552 or 1553 when a low votage is expected. To check disconnect T/C harness C2 pwr off which is the 6 pin plug and check pin A (lower right corner looking at plug)to ground using a digital meter with pwr on, should be 0 voltage. That code is either a short in the cable to the T/C motor or the motor is bad. For parts I use Rockauto as they seem to be the cheapest and great service. If your still having problems do a private message and I'll e-mail you the GM service manual steps.

ADL

I have a print out of the test for the code C0309 and it says to unplug the 4 pin connector at TC and check leads A and B for short to voltage, 0 to .2 volts ok . If ok, replace transfer case shift control module. I have pulled the instrument cluster and light switch but have not found the TCCM . I have a used one to put in it if I can find it.
ToooTall1 I have not checked the wires in the 6 pin connector like you suggested but will check it next.
Thanks for your help . If this does not fix it I will PM you for more info.

Thanks Again
Alvin Langford

ToooTall1

To reset code on TCM turn ignition switch on-off 100 times and it resets the TC module. Try this first to see if you can reset system and then continue if problems come back.

ADL

Changed out the TCCM and that fixed the truck .
Thanks to all who helped.

Alvin