P0A9A: Hybrid/EV Battery Pack Cooling Fan 2 Control Circuit High

P0A9A reports a short to voltage on the control circuit of the second battery cooling fan. No manufacturer publishes this exact code; CARB requires the electronic outputs of battery thermal management to be checked for circuit faults. The fan 1 counterpart P0A85 shows the usual method: GM samples the output while the fan is commanded between 11 % and 100 % duty and counts a voltage above 9 V as a failure, setting a Type B code after 16 of 20 samples. A fan 2 diagnosis would work the same way. Depending on the circuit design the fan runs constantly or stops responding; a constantly running fan can drain the 12 V battery. Open and low faults are P0A96 and P0A99; a mechanically stuck-on fan is P0A98.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

Check engine or hybrid warning
Fan 2 runs constantly or not at all
Possible 12 V battery drain when parked

Most likely causes

Fan 2 control wire shorted to supply voltage
Fan 2 control input internally open or shorted to supply
Corroded connector with leakage to supply

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P0A9A means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
9A: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A9A?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0A9A?

The most common causes are: fan 2 control wire shorted to supply voltage; fan 2 control input internally open or shorted to supply; corroded connector with leakage to supply.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.