P24AC
EGR Cooler Coolant Pump Feedback Circuit Low
The feedback line that confirms pump speed reads below the plausible range - either pump not turning or feedback line shorted to ground.
- 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.
- Feedback line shorted to groundCommon
- Connector pins corroded - high contact resistanceLess likely
- Harness chafing through insulationLess likely
Parts involved
- EGR Cooler Coolant Pump
P24AC 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.