P0AC7: Hybrid/EV Battery Temperature Sensor B Circuit Low

P0AC7 means the voltage of battery temperature sensor B is below its valid range. GM's sensors are NTC thermistors, so a low voltage equals an extremely hot reading, usually from a short to ground. The thresholds differ by program: the 2016 and 2019 tables fail it above 160 °C in 8 of 10 samples; the two-mode tables of 2011 and 2013 above 95 °C in 30 of 40 samples; GM's 2013 table 13OBDG05C below 0.3 V, about 90 °C, in 7 of 10. All are Type B, two trips. GM's Volt bulletin 18-NA-342 names P0AC7 among sensor codes that can set falsely and calls for a software update. A genuine hot pack would trip far lower thresholds first, so treat P0AC7 as an electrical fault.

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 light
Sensor B shows an implausibly high temperature
Charging and drive power reduced

Most likely causes

Sensor B signal shorted to ground inside the pack harness
Thermistor shorted internally
Controller software setting the code falsely (Volt bulletin 18-NA-342)
Moisture or coolant at the sensing board connector

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

It can trigger limp mode.
It affects emissions.

What each character of P0AC7 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
C7: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0AC7?

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 P0AC7?

The most common causes are: sensor B signal shorted to ground inside the pack harness; thermistor shorted internally; controller software setting the code falsely (Volt bulletin 18-NA-342).

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.