What it means
The negative contactor B of the battery charging system reports a control circuit range/performance 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
Negative contactor B is a high-voltage switch in the battery charging path, and its control circuit lets the hybrid module operate and monitor it. This code sets when the circuit response is outside the expected range or does not match the commanded performance, which can limit charging or hybrid power.
Common causes
Most likely first.
- Coil resistance drifted
- High-resistance contact in connector
- Sensor element aged beyond calibration window
Symptoms
- Hybrid-system warning light or message
- Charging may be limited or unavailable
- Reduced hybrid power
How to diagnose it
- Record freeze-frame data and compare live data for the command, reported state, and any available control-circuit feedback for negative contactor B.
- Inspect B's accessible low-voltage connectors and harness for corrosion, loose terminals, heat damage, or wiring strain that could add resistance.
- Use the supported scan-tool output test to command B and check whether its response is delayed, inconsistent, or outside the expected range.
- Following the manufacturer's safety procedure, test coil resistance and circuit voltage drop against the manufacturer's specification.
- If wiring and coil readings meet specification, check the contactor feedback sensing and module control circuit for a calibration or component fault, then verify operation after repair.
Common fixes
- Clean or repair a high-resistance connector terminal in contactor B's control circuit.
- Repair damaged or strained wiring to negative contactor B.
- Replace the contactor if its coil resistance is outside the manufacturer's specification.
- Repair the confirmed feedback-sensing or control-driver fault.
Can I keep driving?
Hybrid power may be reduced and charging may be limited or unavailable; avoid demanding acceleration or long trips until the fault is diagnosed. Stop safely if an overheating or hybrid-system warning appears.
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.