P0406 - EGR Sensor A Circuit High

EGR feedback/position sensor signal high/open.

Code Overview

EGR feedback/position sensor signal high/open.

Common Causes

• Failed EGR position sensor reading too high
• Open circuit in the EGR feedback signal or ground path
• Damaged wiring or poor terminal contact
• Fault inside the EGR valve assembly on integrated systems

Symptoms

• Check-engine light with possible rough idle
• EGR command may not match actual valve position
• Failed emissions test or unstable part-throttle behavior

Diagnostic Steps

1. Inspect EGR wiring and connectors for broken, loose, or corroded terminals
2. Verify the 5-volt reference, ground, and signal circuit
3. Check the EGR position signal sweep while commanding the valve if possible
4. Confirm the circuit fault before replacing the valve or sensor

Repair Difficulty

Moderate

General difficulty estimate for the most common repair path.

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

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Next Steps

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