P0ACA: Hybrid/EV Battery Temperature Sensor C Circuit

Battery temperature sensor C is a further thermistor inside the high-voltage pack, corresponding to sensor 3 in GM's Volt bulletin. P0ACA covers a general electrical fault in its circuit that the controller does not narrow down to low, high or erratic. No manufacturer documents this exact code publicly; GM reports the more specific siblings P0ACB to P0ACE instead. CARB requires temperature sensors of hybrid batteries to be monitored like other input components. Losing one temperature input makes the controller more cautious: expect reduced charge and assist power and a hybrid warning. Since sensors C and B often share the same sensing board, check whether neighbouring sensor codes are stored as well.

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 system or check engine warning
Reduced electric power and regeneration
Further battery sensor codes may be stored

Most likely causes

Poor contact or damaged wire between sensor C and sensing board
Temperature sensor C failed
Fault in the battery controller input stage

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
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

It can trigger limp mode.
It affects emissions.

What each character of P0ACA means

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

Frequently asked questions

Can I keep driving with code P0ACA?

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 P0ACA?

The most common causes are: poor contact or damaged wire between sensor C and sensing board; temperature sensor C failed; fault in the battery controller input stage.

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.