P0406Medium SeverityEmissions

Exhaust Gas Recirculation Sensor A Circuit High

What This Means

The EGR (Exhaust Gas Recirculation) system sensor or control circuit has a malfunction. This circuit monitors and controls EGR valve position for proper exhaust gas recirculation.

Common Symptoms

Check engine light on
Engine knocking or pinging
Rough idle
Failed emissions test

Common Causes

Carbon buildup in EGR passages
Stuck or failed EGR valve
Faulty EGR position sensor
Vacuum supply issue
Wiring damage

Estimated Repair Cost

$150 – $500

Parts and labor (varies by vehicle and location)

Difficulty:Moderate

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For informational purposes only. Diagnostic trouble codes are starting points for diagnosis, not definitive answers. Always consult a certified mechanic for proper diagnosis and repair. Estimated costs vary by vehicle, location, and shop rates.