P0ACF: Hybrid/EV Battery Pack Cooling Fan 3 Control Circuit/Open

Air-cooled traction batteries can use several blowers; P0ACF belongs to the third one and means the battery controller sees an open or otherwise invalid control line while it drives fan 3. CARB 1968.2 (e)(15.2.3)(B) requires the electrical inputs and outputs of the battery thermal management to be monitored like other comprehensive components. No manufacturer publicly documents this code; GM shows the method on fan 1 (P0A81): it checks the control voltage on the driver output and needs 16 failures before a Type B code is stored. Fan 1 and fan 2 have their own sets P0A81 and P0A96. Without the third blower the pack heats up faster, and power is limited.

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

Hybrid or EV system warning light, often with check engine light
Electric drive power reduced when the battery gets warm
No fan noise from the battery area when cooling is expected

Most likely causes

Loose, corroded or unplugged connector at fan 3
Broken control wire between battery controller and fan 3
Fan motor or its built-in driver open internally
Fan output stage in the battery controller defective

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 continuity of the wire between the component and the control module.
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 P0ACF means

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

Frequently asked questions

Can I keep driving with code P0ACF?

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 P0ACF?

The most common causes are: loose, corroded or unplugged connector at fan 3; broken control wire between battery controller and fan 3; fan motor or its built-in driver open internally.

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.