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EmissionsSeverity Medium: diagnose soon

P0405Exhaust Gas Recirculation Sensor "A" Circuit Low

What it means

The EGR position sensor signal is lower than possible, usually a short to ground or a missing 5 V reference.

Symptoms

  • Rough idle or stalling
  • Loss of power, sometimes limp mode
  • Black smoke (diesel) or pinging under load (petrol)

Common causes

  • Signal shorted to ground
  • Missing 5 V reference
  • Faulty position sensor

What to check first

  1. Check the 5 V reference and ground at the valve connector
  2. Back-probe the signal while commanding the valve
  3. Check for other 5 V reference codes
Can I drive with P0405? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0405

EGR valveWiring, typical values, multimeter and scope tests

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P0405: questions and answers

What does P0405 mean?

P0405: Exhaust Gas Recirculation Sensor "A" Circuit Low. The EGR position sensor signal is lower than possible, usually a short to ground or a missing 5 V reference.

What are the symptoms of P0405?

Rough idle or stalling. Loss of power, sometimes limp mode. Black smoke (diesel) or pinging under load (petrol).

What causes P0405?

Signal shorted to ground. Missing 5 V reference. Faulty position sensor.

How do you diagnose P0405?

1. Check the 5 V reference and ground at the valve connector 2. Back-probe the signal while commanding the valve 3. Check for other 5 V reference codes

Can I drive with P0405?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.