Fan relay or fan control circuit stuck closed or driver faulty; Fan motor or its integrated speed control faulty and running when not commanded; Wiring fault such as short to power or chafed harness on the fan control or feedback circuit; Corroded or loose connector causing a false or stuck fan feedback signal; Battery temperature sensor fault or implausible reading causing the system to demand constant cooling; Fault in the battery or hybrid control unit, or outdated software.

P0A98

Hybrid/EV Battery Pack Cooling Fan 2 Stuck On.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
A: AreaHybrid propulsion
98: FaultThe specific fault in that area

What it means

P0A98 is a generic powertrain code meaning the hybrid or EV battery pack cooling fan 2 is stuck on. The control unit commanded the fan off, or expected it to be off, but the fan feedback, speed signal or current draw showed it still running. The exact way the fault is detected and which fan is 'fan 2' depends on the model.

Symptoms

Battery cooling fan running constantly, even with the car off or the battery cool
Noticeably louder fan noise from the battery vent area
Hybrid or powertrain warning light on
Possible reduced hybrid assist or EV performance on some models
Faster than normal drain on the 12 V battery if the fan runs with the car off

Possible causes

Fan relay or fan control circuit stuck closed or driver faultylikely
Fan motor or its integrated speed control faulty and running when not commandedlikely
Wiring fault such as short to power or chafed harness on the fan control or feedback circuitpossible
Corroded or loose connector causing a false or stuck fan feedback signalpossible
Battery temperature sensor fault or implausible reading causing the system to demand constant coolingpossible
Fault in the battery or hybrid control unit, or outdated softwarerare

How to diagnose

Read all stored and pending codes and note freeze frame data, including battery temperatures, fan command and vehicle state when the code set
Check for related codes for other battery fans, temperature sensors or the hybrid control unit, and deal with those first
Listen and observe whether the fan runs with the car off, and whether it stops when the system is shut down
Inspect the fan, its air ducts and intake for blockage, debris or damage, and check the harness and connectors for chafing, water ingress and corrosion
Use a scan tool's active test to command the fan off and on, and compare the commanded state with live fan feedback data
Compare battery temperature sensor readings against each other and against ambient temperature when the car is cold
Check the fan relay (if fitted), supply voltage, ground and control signal at the connector using the manufacturer's wiring information
Check for applicable software updates or technical bulletins for the specific model

How to fix

Replace a faulty fan relay or fan control module as confirmed by testing
Replace the cooling fan if the motor or its internal control is at fault
Repair damaged wiring or connectors, and clear any moisture or corrosion
Replace a faulty battery temperature sensor if readings are implausible
Clear any blocked air ducts or filters, then retest the fan operation
Update the control unit software only where an update is a known fix for this fault

Can I keep driving?

Medium severity

The car can usually be driven short term, but have it checked soon. A fan that runs constantly can flatten the 12 V battery and wear the fan out, and the high voltage system's temperature control may not work properly if the cause is a sensor or control fault.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.