EmissionsSeverity Medium: diagnose soon

P0406Exhaust Gas Recirculation Sensor "A" Circuit High

What it means

The EGR position sensor signal is higher than possible, usually an open signal or ground wire.

Symptoms

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

Common causes

Open signal or ground wire
Signal shorted to voltage
Faulty position sensor

What to check first

Check the sensor ground
Back-probe the signal while commanding the valve
Inspect the connector for heat damage

Can I drive with P0406? 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 P0406

EGR valveWiring, typical values, multimeter and scope tests

Cases with P0406 (0)

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P0406: questions and answers

What does P0406 mean?

P0406: Exhaust Gas Recirculation Sensor "A" Circuit High. The EGR position sensor signal is higher than possible, usually an open signal or ground wire.

What are the symptoms of P0406?

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

What causes P0406?

Open signal or ground wire. Signal shorted to voltage. Faulty position sensor.

How do you diagnose P0406?

1. Check the sensor ground 2. Back-probe the signal while commanding the valve 3. Inspect the connector for heat damage

Can I drive with P0406?

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