P0408 Code: Exhaust Gas Recirculation (EGR) Position Sensor B Circuit High
🟠 Moderate severity · drivable
Drivable, but the EGR valve position can't be read correctly, which can affect idle and emissions.
What P0408 means
The EGR valve position sensor (circuit B) is reporting voltage that's too high. The computer can't tell how far the EGR valve is open, so it can't control exhaust gas recirculation properly.
Symptoms
- Check engine light is on
- Rough idle
- Possible stalling
- Failed emissions test
Common causes
- most common: Faulty EGR valve position sensor
- common: Open or damaged wiring
- less common: Corroded connector
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the EGR valve (position sensor is usually built in) | Yes | $100–400 |
| Repair open sensor wiring | Mechanic | $50–150 |
Frequently asked questions
Can I drive with a P0408 code?
Yes, but the EGR valve position can't be read, which can affect idle and emissions.
What is the most common cause of P0408?
A faulty EGR valve position sensor, usually part of the EGR valve.
How much does it cost to fix a P0408?
Typically $100–$400 for a new EGR valve.
Related codes
P0407
P0407 Code: Exhaust Gas Recirculation (EGR) Position Sensor B Circuit Low
P0406P0406 Code: Exhaust Gas Recirculation (EGR) Position Sensor A Circuit High
P0404P0404 Code: Exhaust Gas Recirculation (EGR) Circuit Range/Performance
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.