P0621 – Generator Lamp Control Circuit

Description

The ECM detects a malfunction in the generator lamp control circuit.

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Symptoms

  • Battery light on
  • Charging issues
  • Stalling

Causes

  • Faulty alternator
  • Wiring issues
  • Poor grounds

Diagnosis

  • Check charging voltage
  • Inspect wiring
  • Test alternator

Repair

  • Replace alternator
  • Repair wiring

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