P0406
PPowertrainEGR Sensor A Circuit High
What does this code mean?
Severity : MediumP0406 means the ECU is receiving too high a voltage from EGR sensor A, usually the EGR valve position sensor. The signal is above its normal operating range, which suggests an open ground, a short to voltage or a failed sensor. The ECU can no longer tell the real valve position.
Symptoms
- Check engine light on.
- Unstable idle or hesitation.
- Loss of power, sometimes limp mode.
- Sometimes no noticeable symptom.
Possible causes
- Faulty EGR position sensor, often built into the valve.
- Open or poorly connected sensor ground.
- Signal wire shorted to a voltage supply.
- Corroded connector or loose pins.
- Less commonly, an ECU fault.
Diagnosis and repair
- Inspect the EGR sensor connector and wiring.
- Measure reference voltage, ground and signal at the connector.
- Check in live data that the signal changes when the valve is commanded.
- Repair the wiring, or replace the faulty EGR valve or sensor.
- Clear the code and confirm with a road test.
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Code
P0406
Category
Powertrain
Prefix
P
Standard
OBD-II / SAE J2012