What it means
The positive contactor B of the battery charging system reports a circuit condition. HV charging path cannot be commanded reliably.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Positive contactor B is a high-voltage switch in the battery charging path; it connects that path when commanded by the hybrid control system. P2BC4 sets when the system detects an electrical fault in contactor B’s circuit and cannot rely on the commanded connection.
Common causes
Most likely first.
- Contactor failed
- Wiring or connector fault
Symptoms
- Hybrid-system warning light or message
- Charging may be unavailable
- Vehicle may not enter READY mode
How to diagnose it
- Record the hybrid-system freeze-frame data and check contactor B command and status to see whether the fault occurs during a charging or READY request.
- With the vehicle powered down according to its service procedure, inspect the low-voltage control connector and harness for damage, corrosion, loose pins, or chafing.
- Check the relevant fuse and low-voltage supply and ground to contactor B using the manufacturer’s wiring information.
- Have the contactor control circuit and contactor response tested using the manufacturer’s procedure; do not probe or disconnect high-voltage components without the required training and precautions.
- Clear the code after repair and verify that the vehicle enters READY and charging operates as intended.
Common fixes
- Repair a loose, corroded, or damaged contactor B control connector or harness.
- Replace a failed low-voltage circuit fuse after finding the cause.
- Replace positive contactor B if its operation fails the manufacturer’s test.
Can I keep driving?
If a hybrid warning appears, charging is unavailable, or the vehicle will not enter READY, do not rely on it for a trip; arrange service or recovery. Do not handle the high-voltage battery or contactor wiring.
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.