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P0406: Exhaust Gas Recirculation Sensor A Circuit High

Severity: Medium Arrange diagnosis soon. If the engine stalls, surges severely, or pings under load, avoid continued driving until the cause is checked.

What does P0406 mean?

The EGR sensor A input is above its allowed electrical range. A signal shorted to power or an open return can falsely report valve position, while an internal sensor fault can do the same.

Generic OBD-II definition: Exhaust Gas Recirculation Sensor A Circuit High. Confirm applicability in your vehicle service information.

Common causes

  • A signal shorted to supply voltage
  • Open sensor ground or signal path
  • Failed EGR feedback sensor

Symptoms

  • Check engine light
  • Possible rough idle or surging
  • Sometimes no noticeable driving symptom

Diagnostic focus

If feedback remains high with the valve commanded closed, determine whether the valve is actually stuck or the signal is false. Those cases need different repairs.

Can I keep driving with P0406?

Severity: Medium Arrange diagnosis soon. If the engine stalls, surges severely, or pings under load, avoid continued driving until the cause is checked.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

  • Check sensor A supply, signal, and return to the wiring diagram
  • Inspect high-input wiring faults
  • Verify feedback during a commanded valve test

Related codes

P0405
Exhaust Gas Recirculation Sensor A Circuit LowP0409
Exhaust Gas Recirculation Sensor A CircuitP0404
Exhaust Gas Recirculation Circuit Range/Performance

Sources & review

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.