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P0405: Exhaust Gas Recirculation Sensor A Circuit Low

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 P0405 mean?

EGR feedback channel A reports a voltage below its permitted range. The computer may be unable to tell whether the valve is open, even if the valve itself is capable of moving.

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

Common causes

  • A signal or reference shorted to ground
  • Faulty EGR feedback sensor
  • Loose terminals or damaged harness

Symptoms

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

Diagnostic focus

A low feedback voltage does not by itself mean low EGR flow. Distinguish the sensor circuit from the valve-control circuit before replacing the complete EGR assembly.

Can I keep driving with P0405?

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

  • Verify A-channel reference and return circuits
  • Inspect for signal shorts to ground
  • Compare commanded EGR movement with the feedback reading

Related codes

P0404
Exhaust Gas Recirculation Circuit Range/PerformanceP0406
Exhaust Gas Recirculation Sensor A Circuit HighP0409
Exhaust Gas Recirculation Sensor A Circuit

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.