LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 530 (Charging System) >> Diagnostic Tests >> DTC P1638: Out-Of-Range Duty Cycle Signal >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Oldsmobile Bravada, 2003 GMC Envoy XL, 2003 GMC Envoy, and 2003 Chevrolet TrailBlazer. 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 ON-VEHICLE TESTING. If diagnostic system check was performed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). See COMPONENT LOCATIONS  . Start engine. Using scan tool, observe GEN F-Terminal parameter in Powertrain Control Module (PCM) data list. If scan tool indicates GEN F-Terminal parameter is 5-95 percent, problem is intermittent. Check wiring and connections. If scan tool does not indicate GEN F-Terminal parameter is 5-95 percent, go to next step.
  3. Turn ON the ignition, leaving the engine OFF. Connect a test light to battery positive voltage and repeatedly probe the generator field duty cycle signal circuit in the harness connector while monitoring the Generator PWM on the scan tool. If the display is affected, go to step  5 . If the display is not affected, go to next step.
  4. Test Gray wire for short or open between generator harness connector terminal "C" and PCM harness connector C2 terminal No. 51 (4.2L) or C2 terminal No. 75 (5.3L). 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 for poor connections at the harness connector of the generator. If problem exists, repair as necessary. After repair, go to step  8 . If problem does not exist, test charging system. See TEST A: CHARGING SYSTEM TEST  .
  6. Inspect PCM harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step  8 . If problem does not exit, go to next step.
  7. Replace PCM. See REMOVAL & 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 DTCs. Operate vehicle within Fail Records conditions as noted. Using scan tool, observe Specific DTC information for DTC P1638. If scan tool indicates DTC P1638 failed this ignition, repeat test beginning at step  2 . If scan tool indicates DTC P1638 passed this ignition, system is okay.
scientia non olet · About LEMON Manuals