P0A98

Code

Generic P — Powertrain

Hybrid/EV Battery Pack Cooling Fan 2 Stuck On

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 33 RU: 20

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Stuck or welded relay/contactor for fan 2 (contacts closed)
Short circuit in wiring (power feed tied to battery voltage) to fan motor
Ground fault or short that forces motor to run
Faulty fan motor internal low-resistance path allowing continuous operation
Failed fan driver or power transistor in BMS/ECU/BCM
Incorrect/erroneous CAN or control signal from battery management system (BMS) or vehicle control unit

Symptoms

Battery cooling fan #2 runs continuously, including with vehicle off or at low battery temps
Unwanted noise from fan area
Reduced HV battery standby time (battery draining faster)
DTC P0A98 stored; possibly related CEL or BMS warnings
High current draw from battery pack when fan should be off

What to check

Observe and confirm fan behavior with ignition on and off, and at different battery temperatures
Scan tool: read freeze frame, live data (fan command, fan actual speed, BMS status) and related codes
Visual inspection of fan 2 wiring, connectors, fuses, and relay locations for damage, corrosion, melted insulation
Measure voltage at the fan motor power and ground pins when command = OFF (use appropriate HV/isolated meter if required)
Check relay coil control and relay contact continuity (remove / isolate relay before measuring)
Check for CAN/BMS communication errors and related modules reporting faults

Signal parameters

Fan 2 control command (BMS/ECU) — expected OFF when fault present
Fan 2 actual speed (RPM) or duty cycle — should be 0 when commanded OFF
Voltage at fan motor supply pin — expected ~0 V when OFF, battery voltage when ON (HV-safe measurement)
Relay coil control voltage/current — should be not energized when OFF
Circuit continuity/resistance across fan motor terminals
Battery pack temperature and BMS coolant temperature (to confirm whether fan command should be OFF)

Diagnostic algorithm

Safety first: follow manufacturer procedures for hybrid/EV high-voltage safety. Disable high-voltage system or isolate batteries if required before accessing HV components.
Use a scan tool to confirm P0A98 and capture live data: fan 2 command, fan 2 actual status/speed, battery temps, related codes.
Visually inspect wiring, connectors, fuses, and relays associated with fan 2 for melted insulation, corrosion, or signs of short/welded contacts.
With the vehicle powered and a spotter, command the fan OFF/ON via scan tool while observing behavior. Do not probe live HV conductors without proper tools and PPE.
Measure voltage at the fan power connector while the command is OFF. If battery voltage is present at the motor with command OFF, suspect stuck relay, short to battery, or welded contact.
Check relay operation: remove or isolate the relay (if serviceable) and check contact continuity and coil control. Replace relay if contacts stuck or coil remains energized when command is OFF.
If relay and wiring appear normal, measure resistance of the fan motor (with vehicle safe to work on per HV procedures). An abnormally low resistance may indicate internal short causing continuous operation — replace motor assembly if confirmed.
Inspect and test the fan driver/control outputs at the BMS/ECU/BCM if wiring and fan motor are good. Compare driver behavior to other channels (fan 1) if available.
Verify CAN and control signals to/from BMS. Reflash or update module software if a known software issue exists and manufacturer bulletin supports it.
After repairs, clear codes and perform a functional test across operating conditions (cold/high pack temp, ignition off/on) to confirm fault is resolved.
Document repairs and recheck for related DTCs; if fault persists, escalate to manufacturer-level diagnostics or module replacement as needed.

Likely causes

Stuck relay or relay weld causing fan power to be continuously applied
Shorted wiring or pin-to-power fault on the fan control circuit
Failed fan motor internal short drawing power even when commanded off
Faulty fan driver output on BMS/ECU forcing motor on

Fault status

⚠️ Status

Battery pack cooling fan 2 reported running when control module commanded OFF. Possible stuck relay, wiring short, motor fault, or driver/module failure.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours