P24AB

Code

Generic P — Powertrain

EGR Cooler Coolant Pump Stuck On

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 47 RU: 25

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Page language: EN

Causes

Stuck or failed EGR cooler coolant pump (mechanical or electrical)
Faulty pump control relay or stuck relay contacts
Shorted control wiring (signal to ground or power)
Failed pump driver in the PCM/ECM
Corroded/poor connector or terminal causing permanent feed
Water, debris or seizure in pump preventing stopping; internal short

Symptoms

Check Engine Light (MIL) illuminated with code P24AB
EGR cooler coolant pump runs continuously (even with ignition off in some cases)
Unusual battery drain or dead battery after parking
Abnormal coolant circulation/flow — heater behavior may be affected
Possible coolant temperature anomalies or rapid cooling of EGR cooler
Visible coolant leaks or contamination near pump or cooler

What to check

Read and record freeze-frame and pending codes with a scan tool
Visually inspect pump, harness, connectors, relays and fuses for damage, corrosion or melted wiring
With ignition ON (engine off) command the pump ON/OFF using a bidirectional scan tool and observe response
Monitor live PIDs for pump command and any feedback signal (if supplied) while commanding pump ON and OFF
Measure voltage at pump power terminal with control OFF and with control ON
Check continuity and resistance of pump motor between its power and ground terminals (compare to specification or other pump)

Signal parameters

Power supply voltage at pump: ~12 V when commanded ON (11–14 V typical)
Voltage at pump control/relay coil when OFF: ~0 V (no feed) — when ON: ~12 V
PWM/duty control (if used): 0–100% duty cycle; frequency typically low-to-mid kHz depending on manufacturer (refer to service data)
Pump running current: typically 0.5–8 A (nominal depending on pump size) — stalled or shorted pump may draw higher current
Motor resistance: low ohms (manufacturer-specific). Infinite resistance indicates open circuit; near 0 ohms indicates short

Diagnostic algorithm

Retrieve codes, freeze-frame, and relevant live data. Confirm P24AB is current and note conditions when set (engine temp, ignition state).
Visually inspect pump assembly, mounting, wiring harness, connectors, and relay/fuse for obvious damage or corrosion. Repair as needed.
Using a scan tool, command the EGR cooler coolant pump OFF and ON while observing whether the pump responds and whether the PCM reports the command correctly. If pump remains ON when commanded OFF, proceed.
Verify power/ground: with key ON (engine off), measure voltage at pump power terminal. With control commanded OFF there should be no feed on the control side. If power present when OFF, isolate between pump and relay/PCm to find stuck feed.
Check relay: locate pump relay (or PCM internal switch). Swap with identical known-good relay or bench-test relay operation. Replace if relay welded/failed.
Measure pump motor resistance (engine off, connector disconnected). Compare to spec. Check motor for internal short/low resistance. If resistance out of range, replace pump.
Measure current draw with clamp meter while pump runs. Excessive current suggests mechanical seizure or electrical fault; low/no current suggests open circuit. Inspect pump mechanically for seizure or debris.
Inspect wiring for shorts to power (constant 12 V) or ground. Wiggle test harness while commanding pump to look for intermittent faults. Repair damaged wiring/connector pins.
If wiring and relay are good but pump still cannot be turned off and command signal from PCM is present/valid, suspect PCM output driver fault — confirm by checking for other PCM-related faults and consult manufacturer procedures before replacing PCM.
After repair or replacement, clear codes, run self-tests, and road test to confirm lamp does not return and pump operates only when commanded.
If issue is intermittent, use data logging to capture events and consider harness protection or replacing suspect components.