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Engine Electrical Diagnostic System Check

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: Presence of DTCs which begin with "U" indicate some other module on class 2 serial data circuit is not communicating.
  1. Load test battery. If battery passes load test, go to next step. If battery does not pass load test, service battery as necessary and go to next step.
  2. Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST E: SCAN TOOL DOES NOT POWER UP  under SYSTEM TESTS.
    3. NOTE: Engine may start during following step. Turn ignition switch to OFF position as soon as you have observed crank power mode.
  3. Using scan tool, access class 2 power mode from diagnostic circuit check function. Rotate ignition switch through all positions while observing ignition switch power mode parameter on scan tool. If ignition switch parameter reading matches ignition switch position for all switch positions, go to next step. If ignition switch parameter reading does not match ignition switch position for all switch positions, go to POWER MODE MISMATCH  under SYSTEM TESTS.
  4. Turn ignition switch to RUN position. Using scan tool, access class 2 power mode from diagnostic circuit check function, attempt to communicate with Body Control Module (BCM), Instrument Panel Cluster (IPC) and Powertrain Control Module (PCM) and Driver Information Center (DIC). If scan tool communicates with any modules, go to next step. If scan tool does not communicate with any modules, go to TEST D: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  under SYSTEM TESTS.
  5. Using scan tool, select DISPLAY DTCS function for all modules (If using a Tech 2, use Class 2 DTC Check feature in order to determine which modules have DTCs set.). Retrieve and record all displayed DTCs, their status and which module set DTC. If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair engine electrical concern by symptom. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
  6. If scan tool displays any DTCs which begin with a "B" or "U", perform appropriate test see DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
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