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Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Chevrolet Corvette. 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). DLC is located below left side of instrument panel. Start engine. Using scan tool, observe GEN F-Terminal parameter in Powertrain Control Module (PCM) data list. If scan tool indicates GEN F-Terminal Signal parameter is 5-95 percent, go to next step. If scan tool does not indicate GEN F-Terminal Signal parameter is 5-95 percent, go to step  4 .
  3. With the scan tool command the generator OFF. If scan tool indicates 0 percent, problem is intermittent. Check wiring and connections. If not, go to next step.
  4. Turn ignition switch to RUN position. Connect a test light to battery positive voltage. Repeatedly probe generator harness connector terminal "C" (Gray wire), while observing Generator Pulse Width Modulation (PWM) on scan tool. If scan tool displays near 100 percent, perform TEST A: CHARGING SYSTEM TEST  under SYSTEM TESTS. If scan tool does not display near 100 percent, go to next step.
  5. Inspect Gray wire for a short or open between generator harness connector terminal "C" and PCM harness connector. See WIRING DIAGRAMS  . If problem exists, repair circuit as necessary. After repair, go to step  8 . If problem does not exist, go to next step.
  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 & 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. Operate vehicle within Fail Records conditions as noted. Check for DTC. If DTC P0622 resets, repeat test beginning at step  2 . If DTC P0622 does not reset, system is okay.
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