P0C42: Hybrid/EV Battery Pack Coolant Temperature Sensor A Circuit

P0C42 is the general circuit code for the first coolant temperature sensor in the liquid loop of a hybrid or EV battery, typically placed at the pack inlet. The battery controller uses it to decide when to pump, heat or chill the coolant. Volvo documents P0C4200 in the battery energy control module of the XC90 T8 plug-in hybrid from model year 2016, as either an intermittent or a permanent entry with a possible check engine lamp; according to technical journal TJ 33546, once the current software is verified the entry is simply erased and no parts are needed. GM reports faults of the same sensor more precisely as P0C44 and P0C45. CARB requires the inputs of the battery thermal management to be monitored. P0C43 covers implausible readings, P0CD5 sensor B.

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 lamp, often without other complaints
Battery cooling or heating running on substitute values
Reduced charging or drive power in hot or cold weather

Most likely causes

Battery controller software flagging the circuit wrongly (Volvo XC90 T8)
Corroded or loose connector or damaged wire at the coolant sensor
Failed coolant temperature sensor A

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

Repair difficulty: hard
It can trigger limp mode.
It affects emissions.

What each character of P0C42 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
C: Subsystem depends on the code range
42: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C42?

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 P0C42?

The most common causes are: battery controller software flagging the circuit wrongly (Volvo XC90 T8); corroded or loose connector or damaged wire at the coolant sensor; failed coolant temperature sensor A.

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.