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Test Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The number(s) below refer to the step number(s) on the diagnostic table.

  1. 4:  Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
  2. 5:  The symptom list in Symptoms will determine the correct diagnostic procedure to use.
  3. 6:  The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
Diagnostic System Check - Engine Electrical

Step Action Yes No
1 Perform the Battery Inspection/Test.
Does the battery pass the test?		 Go to Step 2  Go to Battery Inspection/Test (Non-HP2) 
2 Install a scan tool.
Does the scan tool power up?		 Go to Step 4  Go to Scan Tool Does Not Power Up
3
IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.
  1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
  2. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter.
Does the ignition switch parameter reading match the ignition switch position for all switch positions?		 Go to Step 4  Go to Power Mode Mismatch in Body Control System
4 
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with each module on the class 2 serial data circuit.
    • body control module (BCM)
    • instrument panel cluster (IPC)
    • powertrain control module (PCM)
Does the scan tool communicate with any module on the class 2 serial data circuit?		 Go to Step 5  Go to Scan Tool Does Not Communicate with Class 2 Device (W/O Immobilizer) or Scan Tool Does Not Communicate with Class 2 Device (W/ Immobilizer)
5 
  1. Select the Display DTCs function for each module. (If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules have DTCs set.)
  2. Record all of the displayed DTCs the DTC status and the module which set the DTC.
Does the scan tool display any DTCs?		 Go to Step 6  Go to Symptoms - Engine Electrical  
6  Does the scan tool display any DTC beginning with "U"? Go to Diagnostic Trouble Code (DTC) List Go to Step 7 
7 Does the scan tool display any DTC beginning with "P"? Go to Diagnostic Trouble Code (DTC) List in Engine Controls Go to Step 8 
8 Does the scan tool display any DTC beginning with "B"? Go to Scan Tool Data Definitions Go to Diagnostic Trouble Code (DTC) List 
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