P0A85: Hybrid/EV Battery Pack Cooling Fan 1 Control Circuit High

The controller detects a short to voltage on the control output of battery cooling fan 1. GM runs the test while the fan is commanded between 11 % and 100 % duty: a circuit voltage above 9 V counts as a failure, and 16 fails in 20 samples set a Type B code with MIL after two trips. GM tables from 2013, 2016, 2018 and 2019 hybrid programs carry it, partly via the output stage status flag. Depending on the circuit, the fan may run constantly at full speed or not respond. The low and open counterparts are P0A84 and P0A81; a fan that keeps running without a circuit fault is P0A83.

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 after two trips
Battery fan runs constantly or not at all
Possible 12 V battery drain when parked

Most likely causes

Control wire shorted to a supply voltage
Fan control input internally open or shorted to its supply
Corroded connector creating 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 P0A85 means

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

Frequently asked questions

Can I keep driving with code P0A85?

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 P0A85?

The most common causes are: control wire shorted to a supply voltage; fan control input internally open or shorted to its supply; corroded connector creating 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.