P0A84: Hybrid/EV Battery Pack Cooling Fan 1 Control Circuit Low

The controller detects a short to ground on the control output of battery cooling fan 1. GM tests it while the fan is commanded at low duty: a circuit voltage below about 0.26 V counts as a failure, and 16 fails in 20 samples at 250 ms set a Type B code (MIL after two trips). Another GM hybrid program detects it through the output stage status flag (20 of 25 samples). Mitsubishi lists P0A84 in the BMU and PHEV ECU of the 2018–20 Outlander PHEV among codes caused by a frozen battery heater relay, so meaning can differ by maker. Open and high faults are P0A81 and P0A85. With the output pulled low the fan may not respond, the pack warms up and power can be reduced.

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 cooling fan does not follow commands
Reduced hybrid power when the pack gets warm

Most likely causes

Fan control wire chafed and shorted to ground
Internal short in the fan's control input
Moisture or corrosion in the fan connector
Defective output stage in the controller

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
With the connector unplugged, check whether the signal wire is making contact with ground.
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 P0A84 means

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

Frequently asked questions

Can I keep driving with code P0A84?

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 P0A84?

The most common causes are: fan control wire chafed and shorted to ground; internal short in the fan's control input; moisture or corrosion in the fan connector.

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.