What it means
The negative contactor B of the battery charging system reports a control circuit high 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, operated through a low-voltage control circuit. This code sets when the module detects a control signal above the expected range, which can result from a short to battery voltage or an open coil that prevents the circuit from pulling down as expected.
Common causes
Most likely first.
- Control wire shorted to B+
- Open contactor coil
- Connector pins corroded - high contact resistance
Symptoms
- Hybrid-system warning light or message
- Charging may be unavailable
- Vehicle may not enter READY mode
How to diagnose it
- Record freeze-frame data and check live data for B's command, reported state, and any available control-circuit voltage.
- Inspect the accessible low-voltage control harness and connector for wires shorted together, damage, corrosion, or a loose terminal.
- Following the manufacturer's safe diagnostic procedure, check whether the high circuit reading is present on the harness side with the contactor disconnected as specified.
- Test the control wire for a short to battery voltage and test the contactor coil for an open circuit, comparing results with the manufacturer's specification.
- Repair the cause, clear the code, and confirm the module can command B and the vehicle enters READY.
Common fixes
- Repair control wiring shorted to battery voltage.
- Restore or replace a damaged or corroded connector terminal.
- Replace negative contactor B if its coil is confirmed open.
- Repair a confirmed output-driver fault in the control module.
Can I keep driving?
Charging may be unavailable and READY may be inhibited, so arrange diagnosis before relying on the vehicle. Keep away from high-voltage components.
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.