What it means
The negative contactor B of the battery charging system reports a control circuit low 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, and its low-voltage control circuit operates the switch. This code sets when the module detects a voltage or signal level below the expected range, which can happen if the control wire is grounded or the coil circuit is shorted.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in 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 negative contactor B's command, reported state, and any available control-circuit voltage.
- Inspect the accessible B control wiring for chafing against ground, crushed insulation, corrosion, or damaged connector terminals.
- With the manufacturer's safe procedure followed, disconnect components as specified and check whether the low circuit reading remains on the harness side.
- Test the control wire for a short to ground and the contactor coil for an internal short, comparing readings with the manufacturer's specification.
- Repair the short or high-resistance connection, then clear the code and verify B responds to its command.
Common fixes
- Repair chafed control wiring shorted to ground.
- Clean or repair corroded connector pins for contactor B.
- Replace negative contactor B if its coil is internally shorted.
- Repair a confirmed control-module driver fault.
Can I keep driving?
The vehicle may not enter READY and charging may be unavailable, so avoid depending on it for normal travel. Do not probe or handle the high-voltage side of the contactor.
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.