P24AA

Code

Generic P — Powertrain

EGR Cooler Coolant Pump Control Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 42 RU: 18

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Page language: EN

Causes

Short to battery (power) on the pump control circuit
Stuck or welded relay supplying constant voltage to the pump
Failed EGR cooler coolant pump (internal short or stuck condition)
Corroded, damaged, or loose connector or wiring (intermittent short/high voltage)
Faulty PCM/ECM output driver
Incorrect aftermarket modifications or improper jumpers/repairs

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
EGR cooler coolant pump running continuously or not responding to commands
Reduced EGR cooler performance leading to higher exhaust temperatures / increased NOx
Possible coolant odor or elevated local temperatures near the EGR cooler
Possible coolant loss if related to other coolant system issues (less common)

What to check

Visually inspect wiring harness, connector, and pump for damage, corrosion, or fluid contamination
Check relevant fuses and relays for proper operation
Use a scan tool to verify freeze-frame data and whether the pump is commanded on/off
Backprobe pump connector to measure voltage with key ON and during commanded states
Listen/feel to determine if pump runs continuously or only when commanded

Signal parameters

Control line expected idle voltage: near 0 V when driver is commanding off (may be pulsed when commanded on)
Control line high condition: approaching battery voltage (~12 V) when shorted to battery
Typical PWM control: 0–100% duty cycle when commanded; frequency commonly 100–500 Hz (vehicle dependent)
Pump coil resistance (typical range): ~2–20 ohms (manufacturer dependent) — measure with pump disconnected
Normal steady-state pump current: can be up to several amps (measure with clamp meter while running)

Diagnostic algorithm

Retrieve freeze-frame and live data with a scan tool. Note pump command status and any related freeze data.
Perform a visual inspection of the pump, harness, connector, and nearby wiring for damage, corrosion, or coolant intrusion.
Check fuses and relays related to the EGR cooler coolant pump circuit. Replace any faulty items and retest.
With key ON (engine OFF), backprobe the pump control connector: measure reference/battery voltage and control pin voltage. Compare to expected values.
Command the pump ON/OFF with a scan tool while monitoring the control circuit. Observe whether the voltage changes (PWM or switched ground) or remains high.
Measure pump coil resistance with the pump disconnected. If resistance is outside expected range or shows short to battery, bench test or replace the pump.
If control line is high with pump disconnected, suspect a short to battery or stuck relay. Trace power feed and test relay operation or disconnect relay to isolate the short.
If control line is high only when commanded or shows abnormal waveform, capture the waveform with an oscilloscope to verify PWM characteristics and check for driver faults.
Disconnect the pump and clear codes. If code does not return, suspect pump or harness short. If code returns with pump disconnected, suspect PCM/ECM or circuit short.
If wiring and pump check good, test/replace the PCM/ECM only after confirming all other components and confirming that replacement is required per manufacturer procedures.

Likely causes

Shorted power feed or relay stuck closed supplying constant 12V to pump control
Pump internal failure producing an abnormal voltage signature at the control pin
Connector corrosion or pin short to battery voltage
PCM/ECM driver transistor failed and sourcing voltage on the control circuit

Fault status

⚠️ Status

EGR Cooler Coolant Pump Control Circuit High — control circuit voltage or signal level higher than expected (possible short to battery, pump or connector fault, or driver failure).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours