P24C4
EGR Cooler Bypass Position Sensor Exceeded Learning Limit Bank 1
The bypass valve position sensor learning has reached its software-side limit on bank 1 - typically heavy soot deposits have shifted the mechanical zero beyond the design adaptation range.
- 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.
- Heavy carbon build-up on valve seatCommon
Parts involved
- EGR Cooler Bypass Position Sensor B1
P24C4 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.