P0406 - EGR Sensor A Circuit High
EGR feedback/position sensor signal high/open.
Treat the code as the starting point: compare symptoms, likely causes, and repair paths before pricing parts or moving into an estimate.
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
General difficulty estimate for the most common repair path.
Likely Repairs & Cost Guides
Use symptoms, scan data, and quick checks to confirm the likely repair path before pricing parts. The estimator helps compare repair paths before replacing anything unnecessarily.
Estimator-ready next step after the fault path is confirmed.
Related OBD Codes
Browse nearby code-family pages when the same fault pattern overlaps across systems, such as misfire, lean fuel trim, EVAP sealing, cooling, or charging faults.
Next Steps
Move from code lookup to diagnosis, then estimate the likely repair only after symptoms, causes, and checks point to the same path.