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Voltmeter Displaying High Or Low

  1. Turn off all accessories. Connect scan tool to DLC. Start engine. Using scan tool, check charging system voltage. If voltage is 13-16 volts, go to next step. If voltage is not 13-16 volts, go to step  5 .
  2. Compare scan tool reading to voltmeter reading. If readings are within 2 volts, go to next step. If readings are not within 2 volts, go to step  6 .
  3. Raise engine speed to 2500 RPM. Using scan tool, check charging system voltage. If voltage is 13-16 volts, go to next step. If voltage is not 13-16 volts, go to step  5 .
  4. Ensure engine speed is 2500 RPM. Compare scan tool reading to voltmeter reading. If readings are not within 2 volts, go to step  6 . If readings are within 2 volts, problem is not present at this time.
  5. Perform charging system check. See CHARGING SYSTEM TEST  . If generator is okay, go to step  10 . If generator is faulty, go to step  11 .
  6. Check instrument cluster for incorrect voltmeter reading. If instrument cluster is not operating properly, go to next step. If instrument cluster is operating properly, go to step  8 .
  7. Repair instrument panel cluster as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Recheck system.
  8. Inspect PCM/VCM for incorrect voltmeter reading condition. If PCM/VCM is not operating properly, go to next step. If PCM/VCM is operating properly, go to step  10 .
  9. Replace PCM/VCM. See REMOVAL, OVERHAUL & INSTALLATION - TRUCKS article in ENGINE PERFORMANCE. Recheck system.
  10. Clean all battery cable and generator connectors. Check for open circuit. Repair as necessary. Recheck system.
  11. Replace generator. See GENERATOR  under REMOVAL & INSTALLATION. Recheck system.
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