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DTC codes / P0Axx · Hybrid propulsion / P0A9A

P0A9AHybrid/EV Battery Pack Cooling Fan 2 Control Circuit High

P0A9A indicates that the hybrid or electric vehicle battery pack cooling fan 2 control circuit is showing an abnormally high voltage, which the battery energy control module interprets as an open circuit or a short to power. The computer monitors the fan control circuit and sets this code when the commanded signal does not match the expected voltage, typically because the fan cannot be energized.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light or hybrid system warning light, often with no other noticeable symptoms
  • Reduced hybrid battery performance or forced engine-only operation in hybrids
  • The cooling fan for the high-voltage battery may not run at all, leading to battery overheating in extended driving
  • A warning message on the dashboard indicating a hybrid system fault or reduced power
  • Possible overheating of the battery pack, which may trigger additional codes or a limp mode

Common causes, most likely first

  1. Open or damaged wiring in the cooling fan 2 control circuit, such as a broken wire or corroded connector
  2. Failed cooling fan 2 motor or its internal control module
  3. Faulty battery energy control module or fan control module, though less common
  4. Short to voltage in the control circuit due to chafed wiring or moisture intrusion
  5. Blown fuse or relay dedicated to the cooling fan circuit, though this often affects both fans
  6. Poor ground connection for the fan motor or control module

How to diagnose and fix it

  1. Inspect the cooling fan 2 connector and wiring for corrosion, damage, or loose pins, and repair as needed
  2. Check the fan control circuit for continuity and short to voltage using a multimeter, following the manufacturer's wiring diagram
  3. Test the cooling fan 2 motor directly by applying power and ground to confirm it operates; replace if seized or open
  4. Verify the fan relay and fuse are intact and functioning, replacing any faulty components
  5. Check the ground circuit for the fan motor and control module, cleaning or tightening connections as necessary
  6. If all external circuits and components test good, diagnose the battery energy control module or fan control module for internal faults
  7. Clear the code and perform a road test to verify the repair, ensuring the fan activates when commanded

Don't overlook the simple wiring fault

  • A common oversight is assuming the fan motor is bad when the real issue is a corroded connector or chafed wire in the control circuit, so always perform a thorough visual and electrical inspection first.
  • This code can be set by a short to voltage in the control circuit, which may be intermittent and only appear when the harness is moved or under certain temperature conditions.
  • On some vehicles, the cooling fan for the hybrid battery is controlled by a module that also monitors fan speed; a fan that runs but at incorrect speed can set this code even if the motor spins freely.
  • The battery energy control module may command the fan based on battery temperature, so a faulty temperature sensor can cause the fan not to run and set a circuit code, though this is less common.
  • Replacing the fan motor without checking the control module output can lead to a repeat failure if the module is internally shorted and damages the new fan.

Can I keep driving with P0A9A?

It is generally safe to drive short distances to a repair shop, but avoid heavy acceleration, long trips, or high ambient temperatures because the battery pack may overheat without proper cooling. If the hybrid system warning light is on or performance is reduced, seek service promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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