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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1735 (Data Link Communications) >> Diagnostic Information and Procedures >> DTC U1001 to U1254: Module U1XXX Communication >> Test Description

Test Description

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to the step number on the diagnostic table.

  1. 7:  The module which was not communicating on the class 2 serial data circuit may have set the Loss of Communication DTCs for the modules it was monitoring.
DTC U1001-U1254

Step Action Yes No
Schematic Reference: Data Link Connector (DLC) Schematics (A/T)  or Data Link Connector (DLC) Schematics (M/T) 
Connector End View Reference: Master Electrical Component List in Wiring Systems.
1 Did you perform the Diagnostic System Check for the system exhibiting symptom? Go to Step 2  Go to Control Module References in Body Control System for the applicable Diagnostic System Check
2
IMPORTANT: Use the control module ID number list in order to determine which module 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 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: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 for an open.
Refer to the following:Did you find and correct the condition?		 Go to Step 7  Go to Step 4 
4 Test the class 2 serial data circuits of the module that is not communicating 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 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 class 2 serial data circuits

Refer to the following:
Did you find and correct the condition?		 Go to Step 7  Go to Step 6 
6
IMPORTANT: Perform the programming or set up procedure for the replaced control module if required.
Replace the module that is not communicating. Refer to Control Module References in Body Control System for the applicable replacement procedure.Did you complete the replacement?		 Go to Step 7  -
7 
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the Display DTCs function for the module which was not communicating.
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 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 9 
9
  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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