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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 547 (Charging System) >> Diagnostic Tests >> DTC P0622: Improper Pulse Width Modulated Signal (Gasoline Engine) >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  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). See COMPONENT LOCATIONS  . Start the engine. With scan tool, observe the GEN-F Terminal parameter in the engine data list. If the scan tool indicates that the GEN-F Terminal , problem is intermittent. Check wiring and connections. If parameter is not 5-95 percent, go to next step.
  3. Turn ON the ignition, leaving the engine OFF. Connect a test lamp to battery positive voltage and repeatedly probe the generator field duty cycle signal circuit or F-Terminal in the harness connector while monitoring the Generator F-Terminal Signal on the scan tool. If the Generator F-Terminal Signal display is affected, go to step  5 . If the Generator F-Terminal Signal display is not affected, go to next step.
  4. Test Gray wire for a short or an open between generator harness connector terminal "C" and PCM harness connector C2 terminal No. 52. See WIRING DIAGRAMS  . If problem exists, repair as necessary. After repair, go to step  8 . If problem does not exist, go to step  6 .
  5. Inspect generator harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step  8 . If problem does not exist, perform TEST A: CHARGING SYSTEM TEST  under SYSTEM TESTS.
  6. Inspect PCM harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step  8 . If problem does not exist, go to next step.
  7. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Program PCM. After repair, go to next step.
  8. Review and record scan tool fail records data. Using scan tool, clear DTC's. Start engine. Using scan tool, observe specific DTC Information for DTC P0622 until test runs. If scan tool indicates DTC P0622 passed this ignition, system is okay. If scan tool indicates DTC P0622 failed this ignition, go to step  2 .
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