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Test A: Power Mode Mismatch: Testing

WARNING: This page is about a different car, the 2001 GMC Safari and 2001 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Open driver's door and leave it open during this test. This will disable retained accessory power mode and eliminate this power mode from power mode parameter list.
  1. Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. Turn ignition switch to OFF position. Using scan tool, observe class 2 power mode parameter from diagnostic circuit check menu. If power mode parameter matches ignition switch position, go to next step. If power mode parameter does not match ignition switch position, go to step  6 .
  2. Turn ignition switch to UNLOCK position. Using scan tool, observe class 2 power mode parameter from diagnostic circuit check menu. If power mode parameter matches ignition switch position, go to next step. If power mode parameter does not match ignition switch position, go to step  6 .
  3. Turn ignition switch to RUN position. Using scan tool, observe class 2 power mode parameter from diagnostic circuit check menu. If power mode parameter matches ignition switch position, go to next step. If power mode parameter does not match ignition switch position, go to step  6 .
  4. Turn ignition switch to CRANK position. Using scan tool, observe class 2 power mode parameter from diagnostic circuit check menu. If power mode parameter matches ignition switch position, go to next step. If power mode parameter does not match ignition switch position, go to step  6 .
  5. Turn ignition switch to ACCY position. Using scan tool, observe class 2 power mode parameter from diagnostic circuit check menu. If power mode parameter does not match ignition switch position, go to next step. If power mode parameter matches ignition switch position, concern maybe intermittent, perform appropriate test. See PROBLEM DIAGNOSIS  under INTERMITTENTS.
    6. NOTE: Engine may start during this procedure. Turn ignition switch to OFF position after verifying this power mode.
  6. Turn ignition switch to OFF position. Disconnect Body Control Module (BCM) harness connectors. Using a test light connected to ground, probe BCM ignition switch inputs, while holding ignition switch in position that indicated incorrect power mode. If voltage is present on only inputs specified for ignition switch position, go to next step. If voltage is present at any other input, go to step  8 .
    7. NOTE: Engine may start during this procedure. Turn ignition switch to OFF position after verifying this power mode.
  7. Using a test light connected to ground, probe BCM ignition switch inputs, while holding ignition switch in position that indicated incorrect power mode. If voltage is not present at any input specified for ignition switch position, go to step  9 . If voltage is not present at any input, go to step  11 .
  8. Disconnect 7-pin ignition switch harness connector. Check for short to voltage in ignition switch input circuits to BCM. See WIRING DIAGRAMS  . Check for short between ignition switch input circuits to BCM. If problem is found, repair as necessary and go to step  14 . If no problem is found, go to step  10 .
  9. Disconnect 7-pin ignition switch harness connector. Check for open in ignition switch input circuits to BCM see WIRING DIAGRAMS  . If no problem is found, go to next step. If problem is found, repair as necessary and go to step  14 .
  10. Check for poor, loose or corroded terminals in ignition switch harness connector. If problem is found, repair as necessary and go to step  14 . If no problem is found, go to step  12 .
  11. Check for poor, loose or corroded terminals in BCM harness connectors. If problem is found, repair as necessary and go to step  14 . If no problem is found, go to step  13 .
  12. Replace ignition switch see STEERING COLUMN SWITCHES - ASTRO & SAFARI article. After repairs are made, go to step  14 .
  13. Replace BCM see BODY CONTROL MODULE  under REMOVAL & INSTALLATION. After repair are made, go to next step.
    14. NOTE: Engine may start during this procedure. Turn ignition switch to OFF position after verifying this power mode.
  14. Reconnect all disconnected components. Using scan tool, observe class 2 power mode parameter from diagnostic circuit check menu. Cycle ignition switch through all positions one at a time. If displayed power mode parameter matches actual ignition switch, system is okay. If displayed power mode parameter does not match actual ignition switch, go to step  1 .
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