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2014-2021 MAZDA MAZDA6
2.5L I4•FWD•AUTOMATIC•gas
8 active safety recalls on this vehicle — view recalls
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Repairs0Labor497Torque3366Fluid7DTC1885Battery1Maintenance0Recalls8
P0687high severityPowertrain

ECM/PCM Power Relay Control Circuit High

on 2014-2021 Mazda Mazda6 2.5L I4 · FWD

What this code means

The PCM detects a high voltage condition in the ECM/PCM power relay control circuit. This may indicate a short to voltage or a failed relay.

Symptoms

  • Intermittent stalling
  • No-start condition
  • Power relay stays energized

Common causes

  • Short to voltage in control circuit
  • Faulty power relay
  • Wiring insulation damage
  • PCM fault

Diagnostic steps

  1. Check control circuit for high voltage
  2. Inspect wiring for short to power
  3. Test power relay operation
  4. Verify PCM output signals
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