P0406 — Exhaust Gas Recirculation Sensor A Circuit Low
Can drive — fix at your convenience.
What P0406 means
This code means the engine computer is seeing low voltage from the 'A' EGR position sensor circuit, which it uses to know how far the EGR valve is open. It's often caused by a wiring short to ground, a bad connector, or a failing position sensor inside the EGR valve. Repairs usually involve fixing the wiring or replacing the sensor or EGR valve assembly, and it's typically an affordable fix.
Common symptoms
- Check engine light is on
- Rough or unstable idle
- Minor hesitation or stumble while driving
- Reduced fuel economy
- Failed emissions or smog test
Common causes
- Faulty EGR position sensor
- Short to ground in the sensor wiring
- Corroded or loose EGR connector
- Damaged wiring harness near the EGR valve
- Faulty EGR valve assembly
Typical repair cost
$150 – $450
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0406 code?
Yes, in most cases you can drive normally since this is an emissions sensor issue. You might notice a rough idle or minor hesitation. Get it repaired soon to keep emissions in check and pass a smog test.
How much does it cost to fix a P0406 code?
Most repairs run $150 to $450. A wiring or connector fix is the cheaper end, while replacing the EGR position sensor or the EGR valve assembly with labor lands higher.
Is a P0406 code serious?
It's low severity. The car usually drives normally, but the EGR system can't be controlled accurately without a good position signal, which affects emissions. It's worth fixing but not an emergency.
What does 'circuit low' mean in P0406?
It means the EGR position sensor is sending lower voltage than the computer expects, often signaling a short to ground or a failed sensor. The computer then can't tell the valve's true position, so it sets this code.