Faulty coolant pump 'A' (mechanical failure or electrical fault); Low coolant level or air trapped in the cooling system; Damaged or corroded wiring or connector at the pump; Blown fuse or relay supplying power to the pump; Failed coolant pump control module or driver circuit; Restricted coolant flow due to a blocked hose or radiator

DTC codes / P2Bxx · Hybrid propulsion / P2B28

P2B28Hybrid/EV Battery Pack Coolant Pump A Performance

Q: What does code P2B28 mean?

Hybrid/EV Battery Pack Coolant Pump A Performance. P2B28 indicates that the hybrid or electric vehicle battery pack coolant pump 'A' is not performing as expected, based on the voltage or current feedback the control module receives. The computer has detected that the pump's actual operation does not match the commanded speed or current draw, which can lead to inadequate cooling of the high-voltage battery.

P2B28 indicates that the hybrid or electric vehicle battery pack coolant pump 'A' is not performing as expected, based on the voltage or current feedback the control module receives. The computer has detected that the pump's actual operation does not match the commanded speed or current draw, which can lead to inadequate cooling of the high-voltage battery.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the hybrid system warning light or service vehicle soon light
Reduced electric driving range or power output due to battery temperature management
Audible whining or lack of pump noise when the vehicle is in ready mode
Overheating of the high-voltage battery, potentially leading to a shutdown
Often no symptoms besides the warning light, especially in early stages

Common causes, most likely first

Faulty coolant pump 'A' (mechanical failure or electrical fault)
Low coolant level or air trapped in the cooling system
Damaged or corroded wiring or connector at the pump
Blown fuse or relay supplying power to the pump
Failed coolant pump control module or driver circuit
Restricted coolant flow due to a blocked hose or radiator

How to diagnose and fix it

Check coolant level and inspect for leaks; top up and bleed the system if needed
Inspect the pump connector and wiring for corrosion, damage, or loose pins
Test the pump with a scan tool bidirectional control to command it on and off
Measure voltage and ground at the pump connector to verify power and ground
Check the fuse and relay for the coolant pump circuit
If the pump does not respond, replace the coolant pump 'A'
Clear the code and verify the repair with a test drive

Coolant pump faults that mimic P2B28

A low coolant level or air lock in the system can cause the pump to cavitate and set this code even if the pump is mechanically sound.
The pump may only fail intermittently when hot or under specific load conditions, so a thorough road test with live data monitoring is essential.
Corroded wiring at the pump connector is a common cause that is often overlooked because the pump itself tests fine on the bench.
This code can be set by a faulty control module even when the pump is good, so always verify power and ground before replacing parts.
Some vehicles use the same pump for both battery and power electronics cooling, so a fault in the shared circuit can trigger this code.

Can I keep driving with P2B28?

Driving with this code is not recommended because inadequate battery cooling can lead to reduced performance, battery damage, or a sudden shutdown. Avoid heavy acceleration and long trips until the fault is repaired.

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.