P24A5
EGR Cooler Bypass Control Stuck Open Bank 1
The EGR cooler bypass valve on bank 1 is mechanically stuck in the open (bypassing) position - EGR always bypasses the cooler, gas reaches the intake hotter than designed.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
Common causes
Ordered by how often each turns out to be the cause.
- Valve stuck openCommon
- Carbon or debris buildup preventing free movementLess likely
- Component wear with age - mechanical playLess likely
Parts involved
- EGR Cooler Bypass Valve B1
P24A5 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.