P0CD9: Hybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Intermittent/Erratic

P0CD9 covers a signal from battery coolant temperature sensor B that drops out or jumps for short moments while staying inside the electrical limits most of the time. It is meant for loose terminals, chafed wires or a sensor that misbehaves only with vibration or temperature. Volvo documents ECM-P0CD900 as a permanent entry on several 2021-2022 plug-in hybrids: according to TJ 36929, charging in outside air warmer than 20 °C can light the engine lamp although nothing is broken, and software release 2024 week 34 (version 3.2.4) improves the detection; in any other situation VIDA fault tracing applies. GM does not list P0CD9 and handles the comparable erratic case for sensor A as P0C46 with a step-sum test. Hard short or open faults are P0CD7 and P0CD8.

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 light, often after charging
Jumping outlet temperature value in live data

Most likely causes

False detection after charging in warm weather (Volvo, software update)
Loose or corroded terminal at the sensor or module connector
Chafed harness that moves with the battery or body
Sensor B with an intermittent internal fault

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
Gently move the wiring with the engine running and watch whether the reading changes.
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 affects emissions.

What each character of P0CD9 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
C: Subsystem depends on the code range
D9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0CD9?

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 P0CD9?

The most common causes are: false detection after charging in warm weather (Volvo, software update); loose or corroded terminal at the sensor or module connector; chafed harness that moves with the battery or body.

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.