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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 330 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0621: Generator Light L-Terminal Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

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.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  2. Install a scan tool. Operate vehicle within the conditions for running the DTC. See CONDITIONS FOR RUNNING DTC . Using scan tool, observe the specific DTC Information for DTC P0616 until the test runs. Does the scan tool indicate that DTC P0621 has passed this ignition cycle? If yes, problem is intermittent. If no, go to next step.
  3. Start engine. With scan tool, while observing the Ignition 1 parameter in the engine controls data list, command the Generator L-Terminal Off for 5 seconds and then back on. Does the scan tool indicate a change in voltage each time the Generator L-Terminal is commanded Off and On? If yes, go to step  6. If no, go to next step.
  4. Turn ignition off. Disconnect the generator harness connector. Start engine. Measure the voltage between the generator turn on signal circuit of the generator harness connector and a good ground. Is voltage within 4.5-5.5 volts? If yes, go to step  7. If no, go to next step.
  5. Test the generator turn on signal circuit for a short, high resistance or open. Did you find and correct the condition? If yes, go to step  10. If no, go to step  8.
  6. Test the generator battery voltage output circuit for a high resistance or open. Did you find and correct the condition? If yes, go to step  10. If no, diagnose charging system.
  7. Inspect for poor connections at the harness connector of the generator. Did you find and correct the condition? If yes, go to step  10. If no, diagnose charging system.
  8. Inspect for poor connections at the harness connector of the ECM. Did you find and correct the condition? If yes, go to step  10. If no, go to next step.
  9. Replace ECM. Perform ECM relearn procedures. See ENGINE CONTROL MODULE  under PROGRAMMING. After replacing ECM, go to next step.
  10. Review and record the scan tool Fail Records data. Use scan tool in order to clear the DTC. Operate vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Using scan tool, observe the Specific DTC Information for DTC P0621 until the test runs. Does the scan tool indicate that DTC P0621 failed? If yes, go to step  3. If no, system is okay.
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