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DTC P0620: Generator Performance

  1. If engine electrical diagnostic system check was performed, go to next step. If engine electrical diagnostic system check was not performed, go to ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Connect scan tool to Data Link Connector (DLC). Start engine. Turn all accessories off. Using scan tool, observe IGNITION 1 signal parameter in PCM data list. If voltage is less than 13 volts, go to next step. If voltage is 13 volts or more, go to step  7.
  3. Using scan tool, command GEN-L terminal On and Off. If scan tool does not indicate voltage changes with each command, go to next step. If scan tool indicates voltage level changes with each command, go to step  7.
  4. Turn ignition switch to OFF position. Disconnect generator 4-pin harness connector. Start engine. Using DVOM measure voltage between ground and generator turn-on signal circuit, generator harness connector terminal "B" (Red wire). Using scan tool, command GEN-L terminal On and Off. With generator Off voltage reading should be 0 volts. With generator On, voltage reading should be 5 volts. If voltage reading is not as specified, go to next step. If voltage reading is as specified, go to step  7.
  5. Test generator turn-on signal circuit, generator harness connector terminal "B" (Red wire), for a short to ground. See WIRING DIAGRAMS . If problem exists, repair circuit as necessary and go to step  9. If no problem exists, go to step  7.
  6. Inspect generator harness connector for poor connections. If no problem exists, go to next step. If problem exists, repair circuit as necessary and go to step  9.
  7. Inspect PCM harness connector for poor connections. If problem exists, repair as necessary and go to next step. If no problem exists, go to TEST A: CHARGING SYSTEM TEST  under SYSTEM TESTS.
  8. Replace PCM. After replacement, reprogram PCM. See POWERTRAIN CONTROL MODULE under REMOVAL & INSTALLATION in BODY CONTROL MODULES - MONTANA, SILHOUETTE & VENTURE article in ACCESSORIES & EQUIPMENT. After repairs are made, go to next step.
  9. Review and record scan tool fail records data. Using scan tool, clear DTCs. Start engine. Using scan tool, observe specific DTC information for DTC P0620 until test runs. If scan tool indicates DTC P0620 passed this ignition, system is okay. If scan tool indicates DTC P0620 failed this ignition, go to step  2.
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