P0406 - EGR Sensor A Circuit High
EGR feedback/position sensor signal high/open.
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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
- Inspect EGR wiring and connectors for broken, loose, or corroded terminals
- Verify the 5-volt reference, ground, and signal circuit
- Check the EGR position signal sweep while commanding the valve if possible
- Confirm the circuit fault before replacing the valve or sensor
Repair Difficulty
Moderate
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