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Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 1:  A total loss of communication on CAN serial data link should be diagnosed first.
  2. 8:  The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.
DTC U0100-U0299 (Diesel Engine)

Step Action Yes No
Schematic Reference: Data Link Connector (DLC) Schematics 
Connector End View Reference: Master Electrical Component List in Wiring Systems
1 
  1. Install a scan tool.
  2. Start the engine.
  3. Retrieve DTCs from the engine control module (ECM).
Is DTC U0073 set as current?		 Go to DTC U0073  Go to Step 2 
2
IMPORTANT: Use the DTC list from DTC Descriptors in order to determine which module is not communicating on the controller area network (CAN) serial data bus.
  1. Turn the ignition ON, with the engine OFF.
  2. Test the following circuits of the module that is not communicating on the CAN serial data bus for an open or a short to ground:
    • The battery positive voltage input circuits
    • The battery positive voltage output circuits
    • The ignition voltage input circuits
    • The ignition voltage output circuits
    • The switched battery positive voltage circuits
Refer to the following procedures:Did you find and correct the condition?		 Go to Step 7  Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Test the ground circuits of the module that is not communicating on the CAN serial data bus for an open.
Refer to the following procedures:Did you find and correct the condition?		 Go to Step 7  Go to Step 4 
4 Test the CAN serial data circuits of the module that is not communicating on the CAN serial data bus for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 7  Go to Step 5 
5 Inspect the harness connectors of the module that is not communicating on the CAN serial data bus for poor connections and terminal tension at the following circuits:
  • The battery positive voltage input circuits
  • The battery positive voltage output circuits
  • The ignition voltage input circuits
  • The ignition voltage output circuits
  • The switched battery positive voltage supply circuits
  • The ground circuits
  • The CAN serial data circuits

Refer to the following procedures: 		Go to Step 7  Go to Step 6 
6
IMPORTANT: Perform the programming or set up procedure for the module, if required.
Replace the module that is not communicating on the CAN serial data bus. Refer to Control Module References for the applicable replacement procedure.Did you complete the replacement?		 Go to Step 7  -
7 Select the Display DTCs function for 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 Control Module References in Body Control System Go to Step 8 
8 
  1. Use the scan tool in order to clear the DTCs.
  2. 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?		 Go to Control Module References in Body Control System -
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