P00E4Exhaust Heat Exchanger Exhaust Bypass Valve A Stuck Closed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Some engines, mainly hybrids and fuel-saving designs, have an exhaust heat exchanger behind the catalytic converter that transfers exhaust heat into the coolant for faster warm-up of engine and cabin. A bypass valve sends the exhaust either through the heat exchanger or around it. Documented diagnostics compare the coolant temperature rise at the heat exchanger with the commanded mode: if it behaves like bypass while recovery is commanded, or the other way round, the valve is considered stuck. P00E4 reports the valve stuck closed. How "open" and "closed" map to bypass and recovery is not publicly documented, so both possible effects should be considered: slow warm-up and weak heating, or excessive coolant heat. None of the published manufacturer documents searched uses this code; the explanation follows regulations and comparable manufacturer monitors.
- What you may notice
- Check engine light on
- Slow warm-up and weak heating in winter
- Or high coolant temperature and long fan run-on
- Likely causes
- LikelyValve flap coked or corroded and sticking
- PossibleActuator faulty (electric or vacuum)
- PossibleLinkage or return spring broken
- RareHeat exchanger temperature sensor faulty, simulating a stuck valve
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.