Powertrain, generic (extended)

P24AC EGR Cooler Coolant Pump Feedback Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Electronically commutated coolant pumps often report their state back to the controller on a separate feedback wire, typically as a speed or diagnostic signal. P24AC means that this return line sits below its valid range: shorted to ground, pulled down by a damaged pump, or permanently in an error level the pump uses to signal a dry run or blockage. The control side can be healthy at the same time, which separates it from P24A9. Signal limits are not disclosed by any maker; CARB's rules on rationality and range checks of inputs serve as the reference. Because the controller can no longer confirm pump operation, it may treat the EGR cooler as unprotected and limit EGR.

Likely causes

Feedback wire shorted to ground
Pump signalling an internal fault, dry run or blockage
Corroded feedback pin in the connector

Symptoms

  • Malfunction indicator lamp on
  • EGR possibly reduced

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–450
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

egr cooler coolant pump

Related codes

P24ADP24A8P24A9

References: law.cornell.edu, ms-motorservice.com.