Faulty coolant pump B, such as a worn impeller, seized bearing, or internal electrical failure.; Damaged or corroded wiring or connector at the pump, including chafed wires or water intrusion.; Blown fuse or faulty relay supplying power to the coolant pump circuit.; Low coolant level or air trapped in the cooling system causing the pump to cavitate and underperform.; Restricted coolant flow due to a clogged radiator, heater core, or degraded coolant hoses.; Faulty pump control module or driver circuit within the hybrid/EV control unit.; Software calibration issue in the pump controller requiring a reflash or update.

DTC codes / P2Exx · Hybrid propulsion / P2E42

P2E42Hybrid/EV Electronics Coolant Pump B Performance

Q: What does code P2E42 mean?

Hybrid/EV Electronics Coolant Pump B Performance. P2E42 indicates that the hybrid or electric vehicle's electronics coolant pump B is not performing as expected, meaning the pump's actual speed or flow does not match the commanded value. The computer monitors the pump's feedback signal and sets this code when the performance deviates from the expected range for a calibrated time, often due to electrical or mechanical faults in the pump circuit or the pump itself.

P2E42 indicates that the hybrid or electric vehicle's electronics coolant pump B is not performing as expected, meaning the pump's actual speed or flow does not match the commanded value. The computer monitors the pump's feedback signal and sets this code when the performance deviates from the expected range for a calibrated time, often due to electrical or mechanical faults in the pump circuit or the pump itself.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or service vehicle soon message, often with no other noticeable symptoms.
Reduced hybrid system performance or a forced limp mode to protect electronics from overheating.
Overheating warning for the hybrid/EV electronics, which may lead to shutdown of the electric drive.
Audible whining or humming from the coolant pump that changes with speed or stops entirely.
Inconsistent coolant temperature readings or rapid fluctuations in the electronics coolant temperature gauge.
In rare cases, the vehicle may fail to start or enter a 'ready' state due to safety interlocks.

Common causes, most likely first

Faulty coolant pump B, such as a worn impeller, seized bearing, or internal electrical failure.
Damaged or corroded wiring or connector at the pump, including chafed wires or water intrusion.
Blown fuse or faulty relay supplying power to the coolant pump circuit.
Low coolant level or air trapped in the cooling system causing the pump to cavitate and underperform.
Restricted coolant flow due to a clogged radiator, heater core, or degraded coolant hoses.
Faulty pump control module or driver circuit within the hybrid/EV control unit.
Software calibration issue in the pump controller requiring a reflash or update.

How to diagnose and fix it

Verify coolant level and condition; top off or replace coolant if low or contaminated, and bleed the system of air.
Perform a visual inspection of the pump, connectors, and wiring for damage, corrosion, or loose connections.
Check the fuse and relay for the coolant pump circuit and replace if faulty.
Use a scan tool to command the pump on and off while monitoring live data for pump speed and coolant temperature to confirm operation.
Measure voltage and resistance at the pump connector to rule out wiring faults; compare with manufacturer specifications.
If electrical checks pass, remove the pump and inspect for mechanical binding or impeller damage; replace if necessary.
After repair, clear the code and perform a road test with the scan tool to verify the pump meets commanded performance and the code does not return.

Coolant pump faults that mimic other failures

A failing coolant pump B can cause the hybrid system to derate power without setting any other codes, leading technicians to chase transmission or battery issues first.
Air pockets in the cooling system are a common cause of this code after a coolant service, and the pump may test fine once properly bled.
The pump may pass a simple spin test but still set P2E42 under load if its internal electronics degrade with heat, so live data during a drive is essential.
Corroded pins in the pump connector often go unnoticed because the connector looks secure; a voltage drop test under load reveals the problem.
On some vehicles, a weak 12-volt auxiliary battery can cause the pump to run slowly and set this code, so always check battery health before replacing the pump.

Can I keep driving with P2E42?

It is not recommended to continue driving with P2E42 because a failed coolant pump can lead to overheating of the hybrid/EV electronics, which may cause a sudden loss of power or expensive damage. If you must drive, limit the distance to a nearby repair shop and avoid heavy acceleration or long trips.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.