Diagnostic Aids

A poor connection at the inoperative module may cause this code to set.
An improperly powered module may cause this code to set.

DTC U0100 To U0299: Lost Communication With Transmission Control Module (TCM) Or Electronic Brake Control Module (EBCM)

Step	Action	Yes	No
Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Computer/Integrating Systems Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Install a scan tool. Turn ON the ignition, with the engine OFF. Attempt to communicate with the electronic brake control module (EBCM) and the transmission control module (TCM). Were you able to communicate with EBCM and TCM?	Go to Step 6	Go to Step 3
3	Turn OFF the ignition. Test all the high speed GMLAN serial data circuits between the EBCM, the TCM, and the Engine Control Module (ECM) for an open. Did you find and correct the condition?	Go to Step 6	Go to Step 4
4	IMPORTANT: Use the DTC list from DTC Descriptors to determine the closest module to DLC which is not communicating. Test the following circuits of the module that is not communicating, for an open or a short to ground: The battery positive circuits The battery voltage output circuits The switched battery positive voltage circuits Did you find and correct the condition?	Go to Step 6	Go to Step 5
5	Replace the module that is not communicating. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 6	-
6	Retrieve DTCs from the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"?	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information	Go to Step 7
7	Use the scan tool in order to clear the DTCs. Continue diagnosing or clearing the DTCs until all the modules have been diagnosed and all the DTCs have been cleared. Did you complete the action?	System OK	-