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Home >> Chevrolet >> 2001 >> Monte Carlo SS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0620: Generator Performance >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
  2. Install scan tool. Start engine. Using scan tool, observe GENERATOR PWM parameter in PCM data list. If scan tool indicates GENERATOR PWM parameter is 5-95 percent, go to next step. If scan tool indicates GENERATOR PWM parameter is not 5-95 percent, go to step  4.
  3. Using scan tool, command generator off. If GENERATOR PWM equals zero percent, see INTERMITTENT TROUBLE CODE DETERMINATION  under ON-BOARD DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM. If GENERATOR PWM does not equal zero percent, go to next step.
  4. Turn ignition off. Disconnect generator harness connector. Start engine. Measure voltage between generator connector terminal "B" (Red wire) and ground. Using scan tool, command generator on and off. Voltage should be zero volts with generator off and 5 volts with generator on. If voltage is as specified, go to next step. If voltage is not as specified, go to step  6.
  5. Turn ignition on, engine off. Using a test light connected to battery voltage, repeatedly probe generator connector terminal "C" (Gray wire) while monitoring GENERATOR PWM on scan tool. If GENERATOR PWM display is affected, go to step  8. If GENERATOR PWM display is not affected, go to step  7.
  6. Check Red wire between generator and PCM for short or open. If problem was found, repair as necessary. After repairs, go to step  11. If problem was not found, go to step  9.
  7. Check Gray wire between generator and PCM for short or open. If problem was found, repair as necessary. After repairs, go to step  11. If problem was not found, go to step  9.
  8. Check generator connector for poor connections. If problem was found, repair as necessary. After repairs, go to step  11. If problem was not found, see appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
  9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  11. If problem was not found, go to next step.
  10. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  11. Review and record scan tool FREEZE FRAME/FAILURE RECORDS data. Clear any DTCs. Operate vehicle within code enable criteria. Using scan tool, monitor SPECIFIC DTC INFO for this DTC. If scan tool indicates this DTC failed this ignition cycle, go to step  2. If scan tool indicates this DTC passed this ignition cycle, system is okay.
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