P24D4

Code

Generic P — Powertrain

EGR Cooler Coolant Pump Feedback Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 43 RU: 37

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Page language: EN

Causes

Open or short in pump feedback wiring (open, short to ground, short to battery)
Corroded, loose, or damaged connector at pump or ECM
Failed EGR cooler coolant pump (motor, internal sensor or tach output)
Blown fuse or failed relay supplying the pump
Poor ground at pump or ECM
Faulty ECM (rare)

Symptoms

MIL/CEL (check engine light) illuminated
EGR cooler pump not running when commanded (no cooling flow)
Engine may enter limp mode or reduced EGR function
Elevated EGR cooler temperatures or EGR cooler overheating
Coolant level drop or localized coolant smell if pump/cooler leaking
DPF regen or exhaust control issues if EGR cooling fails

What to check

Read and record freeze frame and all stored DTCs with a scan tool
Perform an active test: command EGR cooler pump ON/OFF while monitoring feedback and pump operation
Visually inspect pump, connectors, and wiring for damage, corrosion, or contamination
Check coolant level and condition
Inspect and test related fuses and relays
Backprobe pump connector to measure supply voltage, ground and feedback while commanding pump

Signal parameters

Supply voltage to pump when commanded: approx. battery voltage (nominal 11–14.5 V) at pump positive terminal
Feedback signal: typically a pulsed tachometer or switched return—0–12 V pulses or a low-speed frequency signal when pump runs (frequency varies with pump speed)
Expected feedback when idle/command OFF: steady at a defined level (often 0 V or a pull-up voltage) with no pulses
Pump motor resistance (DC): typically low, often in the range of 1–10 ohms (manufacturer-specific)
Current draw when running: commonly 0.5–5 A depending on pump size; abnormally high current suggests mechanical bind or electrical short
ECM input impedance for feedback: high; feedback pulses should be clean, not noisy or stuck

Diagnostic algorithm

Retrieve freeze frame data and all DTCs. Confirm P24D4 is current and note conditions when set.
Visual inspection: check pump, hoses, connectors, wire insulation, and coolant level. Repair obvious damage.
Check fuses/relays: verify fuse for pump is good and relay clicks/operates. Replace if faulty.
Active test with scan tool: command pump ON and observe whether pump runs (listen/feel) and whether any feedback is present.
Measure supply voltage at pump connector while commanded ON. Should be approx. battery voltage. If no voltage, trace supply side (fuse, relay, wiring) back to power source.
Backprobe feedback pin at pump connector while commanding pump ON. Look for pulse signal or expected feedback level. If no feedback but supply present, suspect pump internal fault.
Measure DC resistance of pump motor (with battery disconnected). Compare to specification or expected low-Ohm value. Very high/OL = open; very low/near short = possible shorted winding.
Check continuity and for shorts between feedback wire and ground or battery. Wiggle harness while monitoring to find intermittent faults.
If feedback signal present at pump connector but not at ECM input, harness issue between pump and ECM — inspect, repair, or replace wiring/connector.
If harness and pump test good but ECM sees no/invalid feedback, consider ECM input fault or software issue — verify wiring and reflash or replace ECM only after excluding wiring and pump faults.
After repairs, clear codes and perform functional test and road test to verify the fault does not return.