Fan control relay or driver stuck in the on position; Short to power or to the control line in the fan wiring or connector; Faulty fan speed or feedback signal giving a false stuck-on reading; Faulty battery temperature sensor causing the system to demand constant cooling; Blocked or restricted cooling duct or air intake making the fan run continuously; Fault inside the battery control unit or hybrid control unit, or outdated software where the manufacturer lists a known issue.

P0AD1

Hybrid/EV Battery Pack Cooling Fan 3 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
D1: FaultThe specific fault in that area

What it means

P0AD1 is a generic powertrain code meaning the hybrid or EV battery pack cooling fan 3 is stuck on. The control unit commands the fan off, or expects it to be off, but sees it still running or sees feedback showing it is energised. The exact fan numbering and how the fault is detected depend on the make, model and battery design.

Symptoms

Battery cooling fan running constantly, even with the car off or the pack cool
Noticeable fan noise from the rear seat, boot or battery area
Hybrid or EV system warning light or malfunction message
Reduced battery performance or limited power in some cases
Slightly higher 12 V battery drain if the fan keeps running after shut-down

Possible causes

Fan control relay or driver stuck in the on positionlikely
Short to power or to the control line in the fan wiring or connectorlikely
Faulty fan speed or feedback signal giving a false stuck-on readingpossible
Faulty battery temperature sensor causing the system to demand constant coolingpossible
Blocked or restricted cooling duct or air intake making the fan run continuouslypossible
Fault inside the battery control unit or hybrid control unit, or outdated software where the manufacturer lists a known issuerare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including battery temperatures and fan command status
Check for related codes for other cooling fans, temperature sensors or the battery control unit, and deal with those first
Listen and observe whether the fan runs with the system off and the key out, and whether it responds to commands
Inspect the fan wiring, connectors and relay or fuse for damage, corrosion, moisture or chafing
Compare the battery temperature sensor readings with each other and with actual pack temperature
Use a scan tool to command the fan on and off and watch the commanded and actual states
Check the fan intake and ducts for debris, blockage or a loose or missing cover
Test the fan circuit supply, ground and control signal against the manufacturer wiring diagram, following the high-voltage safety procedure for the model

How to fix

Replace a faulty fan relay or control driver
Repair or replace damaged wiring or connectors in the fan circuit
Replace a faulty fan or fan speed feedback sensor
Replace a faulty battery temperature sensor
Clear blocked ducts or intakes and refit any loose covers
Update or repair the control unit only where a fault or outdated software is confirmed by the manufacturer

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but book it in soon. A fan that never stops can flatten the 12 V battery and may hide a cooling or sensor problem, so stop driving if power is reduced or other warnings appear. Work on the battery area should only be done by someone trained in high-voltage safety.

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