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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 259 (Charging System) >> Diagnostic Tests >> DTC P0620: Fault Detection Circuit Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. If diagnostic system check was performed, go to next step. If diagnostic system check was not performed, go to ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK  .
  2. Connect scan tool to Data Link Connector (DLC). See COMPONENT LOCATIONS  . Start engine. Using scan tool, observe ignition 1 signal parameter in PCM data list. If scan tool indicates voltage is less than 13 volts, go to next step. If scan tool indicates voltage is greater than 13 volts, go to step  6 .
  3. Using scan tool, command GEN-L terminal ON and OFF. If voltage level does not change with each command, go to next step. If voltage level changes with each command, go to step  8 .
  4. Turn ignition switch to LOCK position. Disconnect generator connector. Start engine. Measure voltage between generator turn-on signal circuit and ground. Using scan tool, command GEN-L Terminal ON and OFF. If voltage is zero volt with generator OFF and 5.0 volts with generator ON, go to step  7 . If voltage is not as specified, go to next step.
  5. Test Red wire for a short or open between generator harness connector terminal "B" and PCM harness connector C2 terminal No. 61. See WIRING DIAGRAMS  . If short or open was not found, go to step  8 . Repair circuit as necessary, then go to step  10 .
  6. Test Red wire for a short to battery positive voltage between generator harness connector terminal "B" and PCM harness connector C2 terminal No. 61. See WIRING DIAGRAMS  . If short was not found, go to step  8 . Repair circuit as necessary, then go to step  10 .
  7. Inspect generator harness connector for poor connections. Repair as necessary, then go to step  10 . If connections are okay, see TEST A: CHARGING SYSTEM TEST  .
  8. Inspect PCM harness connector for poor connections. If connections are okay, go to next step. Repair as necessary, then go to step  10 .
  9. Replace PCM. After replacement, reprogram PCM. See REMOVAL, OVERHAUL & INSTALLATION . Go to next step.
  10. Review and record scan tool Fail Records data. Using scan tool, clear DTCs. Operate vehicle within Fail Records conditions. Using scan tool, observe Specific DTC Information for DTC P0620. If scan tool indicates DTC P0620 failed this ignition, go to step  2 . If scan tool indicates DTC P0620 passed this ignition, system is okay.
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