What it means
The ECM detects a generic fault on the charge air cooler coolant temperature B sensor circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
How it works
The charge air cooler uses coolant to remove heat from compressed intake air, and sensor B reports the coolant temperature to the engine control module. P2AC7 sets when the module detects a fault in sensor B's circuit, so it cannot rely on that temperature reading to manage charge-air cooling and engine output.
Common causes
Most likely first.
- Sensor failed
- Wiring or connector fault
Symptoms
- Check-engine light may be on
- Reduced engine power
- Poor acceleration, especially under load
How to diagnose it
- Save freeze-frame data and review charge air cooler coolant temperature sensor B data, comparing it with sensor A or ambient and engine temperatures when the engine is cold.
- Inspect sensor B's connector and nearby wiring for coolant intrusion, corrosion, loose pins, chafing or heat damage.
- Check the sensor B circuit supply, ground and signal using the manufacturer's wiring information and specification.
- If the wiring is intact, test sensor B's resistance or output across temperature changes using the specified procedure.
- Check the charge air cooler coolant level and look for leaks if the temperature readings or reduced power suggest a cooling problem.
Common fixes
- Reconnect sensor B securely and clean or repair corroded connector terminals.
- Repair damaged wiring in the charge air cooler coolant temperature sensor B circuit.
- Replace sensor B if its output fails the manufacturer's test.
- Repair a charge air cooler coolant leak and refill or bleed the system as specified if low coolant is found.
Can I keep driving?
Drive gently and avoid heavy acceleration or towing, especially if power is reduced, because the engine may not manage charge-air temperature as intended. Stop if the engine overheats or coolant is leaking, since continued operation can cause further damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.