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DTC codes / P0Axx · Hybrid propulsion / P0A85

P0A85Hybrid/EV Battery Pack Cooling Fan 1 Control Circuit High

P0A85 means the hybrid or electric vehicle battery pack cooling fan control circuit is reporting a high-voltage condition, which the computer interprets as an open circuit or a short to voltage on the fan control wire. The computer commands the fan on and monitors the control circuit, and it sets this code when the feedback voltage stays above the expected range for the commanded duty cycle.

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

Symptoms you may notice

  • Hybrid or EV battery cooling fan may not run at all, even when the battery is hot
  • Often no symptoms besides the warning light, especially if the battery is not yet heat-soaked
  • Reduced hybrid system power or a forced limp mode when battery temperature rises
  • Battery pack temperature warning message on the dash
  • Possible active grille shutter or cooling system faults stored alongside this code
  • Fan may run continuously at full speed on some vehicles as a failsafe

Common causes, most likely first

  1. Open circuit in the fan control wire, such as a broken wire or unplugged connector
  2. Corroded or water-intruded fan connector pins causing high resistance
  3. Failed battery pack cooling fan motor with an open internal winding
  4. Faulty fan control module or driver inside the battery pack assembly
  5. Short to voltage on the control circuit from chafed wiring near the pack
  6. Poor ground connection for the fan motor or control module
  7. Failed hybrid/EV battery temperature sensor giving false feedback to the control strategy

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data for P0A85 and any companion codes before clearing anything
  2. Inspect the battery pack cooling fan connector and wiring for corrosion, water intrusion, and loose pins
  3. Measure resistance of the fan motor windings and compare to specification to rule out an open motor
  4. Back-probe the fan control circuit with a multimeter and check for voltage where the commanded signal should be low
  5. Check the fan ground circuit for excessive voltage drop under load
  6. Command the fan on with a scan tool and verify actual fan operation and current draw
  7. If the circuit and motor test good, diagnose the fan control module or battery pack controller per manufacturer procedures

What the high-voltage reading really means

  • A high control circuit reading usually means the control wire is open or shorted to voltage, not that the fan itself has failed, so replacing the fan first often wastes money.
  • Water intrusion at the battery pack cooling fan connector is a common hidden cause, especially on vehicles that have been through deep water or have clogged pack vents.
  • Some vehicles set P0A85 when the 12-volt supply to the fan control module is low or intermittent, so check charging system and battery condition before chasing the fan circuit.
  • A failed battery temperature sensor can make the controller command the fan incorrectly and set a control circuit code, so review live temperature data before condemning wiring.
  • Clearing the code without repairing the circuit can lead to battery pack overheating and permanent pack damage, so treat this as a real cooling fault rather than a nuisance light.

Can I keep driving with P0A85?

You can usually drive short distances at moderate speeds with the warning light on, but avoid heavy acceleration, long climbs, and fast charging because the battery pack can overheat without cooling. If the dash shows a battery temperature warning or the vehicle enters limp mode, stop and have it diagnosed before continuing.

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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