What Does P0AD1 Mean?
Hybrid battery pack cooling fan 3 is stuck in the on position and will not turn off when commanded by the BMS. This indicates the fan control circuit has failed in a way that continuously powers the fan, or a relay or driver transistor has welded closed. While the fan running continuously provides cooling, it drains the 12V or HV accessory system unnecessarily and may overcool the battery in cold conditions.
Common Causes
30%
Welded or stuck-closed fan control relay
25%
Shorted fan control driver transistor in the BMS
20%
Short to power in the fan control circuit wiring
15%
BMS software glitch continuously commanding the fan on
10%
Aftermarket wiring modification bypassing normal fan control
Diagnostic Steps
1
Verify the fan continues running with the key off and all systems commanded to sleep; this confirms it is truly stuck on rather than responding to a legitimate cooling request.
2
Locate and test the fan control relay; check for welded contacts by measuring resistance across the relay contacts with the control signal removed.
3
Disconnect the BMS fan control output and check if the fan stops; if it does, the BMS driver is failed-on internally.
4
Inspect the wiring harness for a short to battery positive that could bypass the control circuit and directly power the fan motor.
5
Check for BMS software updates or TSBs that address continuous fan operation faults.
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
Hybrid battery pack cooling fan 3 is stuck in the on position and will not turn off when commanded by the BMS. This indicates the fan control circuit has failed in a way that continuously powers the fan, or a relay or driver transistor has welded closed. While the fan running continuously provides c...
The most common cause of P0AD1 (Hybrid Battery Pack Cooling Fan 3 Stuck On) is: Welded or stuck-closed fan control relay
Typical repair costs for P0AD1 range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A continuously running fan poses minimal immediate safety risk but can drain the 12V battery when the vehicle is parked, potentially causing a no-start condition. In cold climates, overcooling the battery reduces efficiency and can accelerate degradation. The constant power draw also reduces overall EV range.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0AD1 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Battery Cooling System
Difficulty
Type
Generic (SAE)
Recommended Tools
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