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-U0299

Step	Action	Yes	No
Schematic Reference: Data Communication Schematics Connector End View Reference: Master Electrical Component List
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	IMPORTANT: Use the DTC Descriptor list to determine the module 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 Refer to the following: Control Module References for the applicable schematic Circuit Testing Wiring Repairs Did you find and correct the condition?	Go to Step 7	Go to Step 3
3	Turn OFF the ignition. Test the ground circuits of the module that is not communicating for an open. Refer to the following: Control Module References for the applicable schematic Circuit Testing Wiring Repairs Did you find and correct the condition?	Go to Step 7	Go to Step 4
4	Test the high speed GMLAN serial data circuits of the module that is not communicating for an open. Refer to the following: Control Module References for the applicable schematic Circuit Testing GMLAN Wiring Repairs Did you find and correct the condition?	Go to Step 7	Go to Step 5
5	Test the following circuits of the module that is not communicating for poor connections: The battery positive voltage circuits The battery voltage output circuits The switched battery positive voltage circuits The ground circuits The high speed GMLAN serial data circuits Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	Go to Step 7	Go to Step 6
6	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 7	-
7	Reconnect all disconnected modules. Turn ON the ignition, with the engine OFF. Use the scan tool in order to clear the DTCs. Does the scan tool still display any other current DTCs?	Go to Diagnostic System Check - Vehicle	System OK