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Diagnostic System Check - Engine Electrical

WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform the Battery Inspection/Test. See BATTERY TESTING & INSPECTION in appropriate GENERATORS & REGULATORS article in ELECTRICAL. Does the battery pass the test? If so, go to next step.
  2. Install a scan tool. Turn ON the ignition, with the engine OFF. Does the scan tool power up? If so, go to step  4. If not, go to SCAN TOOL DOES NOT POWER UP in BODY CONTROL MODULES article, under ACCESSORIES & EQUIPMENT.
    NOTE: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.
  3. Access the CLASS 2 POWER MODE in the DIAGNOSTIC CIRCUIT CHECK on the scan tool. 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 positions for all switch positions? If so, go to next step. If not, go to POWER MODE MISMATCH in BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
    NOTE: Lack of communication may be because of 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.
  4. Turn ON the ignition, with the engine OFF. Attempt to communicate with each of the following modules on the class 2 serial data circuit:
    • Body Control Module (BCM)
    • Powertrain Control Module (PCM)
    • Instrument Panel Cluster (IPC)
    Does the scan tool communicate with all modules on the class 2 serial data circuit? If so, go to next step. If not, go to DATA LINK COMMUNICATIONS SYSTEM in BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
    NOTE: The symptom list in Symptoms will determine the correct diagnostic procedure to use.
  5. 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.) Record all of the displayed DTCs the DTC status and the module which set the DTC. Does the scan tool display any DTCs? If so, go to next step. If not, go to SYMPTOMS - ENGINE ELECTRICAL .
    NOTE: The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will collect all the available information before you perform tests.
  6. Does the scan tool display any DTC beginning with "U"? If so, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If not, go to next step.
  7. Does the scan tool display any DTC beginning with "P"? If so, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTIC article under FAULT ISOLATION in ENGINE PERFORMANCE. If not, go to next step.
  8. Does the scan tool display any DTC beginning with "B"? If so, go to SCAN TOOL DATA DEFINITIONS in BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If not, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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