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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> Electrical >> Charging Systems >> Charging System >> Diagnostic Tests >> DTC P1637: High Or Low Generator Turn On Signal >> Diagnostic Procedure

Diagnostic Procedure

  1. If diagnostic system check was not performed, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. If diagnostic system check was performed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). DLC is located below left side of instrument panel. Start and idle engine. Using scan tool, observe Generator L-Terminal parameter. If scan tool displays Inactive, go to next step. If scan tool does not display Inactive, go to step  4.
  3. Connect test light between ground and generator connector BAT terminal. See WIRING DIAGRAMS . If test light illuminates, go to next step. If test light does not illuminate, problem is intermittent. Check wiring and connections.
  4. Inspect generator harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step  11. If problem does not exist, go to next step.
  5. Turn ignition switch to OFF position. Disconnect PCM connector C2. PCM is located at right side of engine compartment. Using DVOM, test Red wire for high resistance or open between PCM harness connector and generator harness connector terminal "B". See WIRING DIAGRAMS . If DVOM indicates continuity, go to next step. If DVOM does not indicate continuity, go to step  8.
  6. Using DVOM, test Red wire between generator harness connector "B" terminal and battery ground. See WIRING DIAGRAMS . If DVOM indicates continuity, go to next step. If DVOM does not indicate continuity, go to step  9.
  7. Inspect PCM harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step  13. If problem does not exist, go to step  9.
  8. Repair open or high resistance in generator circuit. See WIRING DIAGRAMS . After repair, go to step  13.
  9. Repair short to ground in generator circuit. See WIRING DIAGRAMS . After repair, go to step  13.
  10. Replace PCM. See REMOVAL & INSTALLATION article in ENGINE PERFORMANCE. Program PCM. After repair, go to next step.
  11. Disconnect generator harness connector. Start engine. Measure voltage between ground and generator connector "B" terminal (Red wire). If voltage is equal to or greater than 10 volts, go to step  13. If voltage is not equal to or greater than 10 volts, go to next step.
  12. Replace generator. See GENERATOR  under REMOVAL & INSTALLATION. After repair, go to step  13.
  13. Using scan tool, clear DTC's. Start vehicle and run at greater than 1000 RPM. Check for DTC. If DTC P1637 resets, repair test beginning at step  2. If DTC P1637 does not reset, system is okay.
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