What it means
The control module detects a fault in the hybrid/EV battery negative contactor circuit.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The negative contactor is the high-voltage switch that connects the battery’s negative side to the drive system. The control module monitors its coil circuit and switching response; this circuit fault can reflect an open coil, wiring problem, or a contactor that cannot close, but does not specifically mean it is stuck open.
Common causes
Most likely first.
- Contactor coil open or failed
- Wiring or connector fault
- Contactor stuck or unable to close
Symptoms
- Check-engine or hybrid-system warning light
- Hybrid system may not start or operate
- Reduced or unavailable electric drive
How to diagnose it
- Read all hybrid-system codes and freeze-frame data first to identify related negative-contactor, battery, or interlock faults.
- Check whether the vehicle enters ready mode and whether electric drive is reduced or unavailable.
- With the vehicle safely powered down according to service information, inspect the negative contactor's accessible wiring and connectors for corrosion, looseness, damage, or heat marks.
- Use scan-tool data during the manufacturer's check to compare the negative contactor command and reported state.
- Have a qualified hybrid technician test the negative contactor coil and control circuit against the manufacturer's specification, without probing high-voltage terminals.
- If the coil and wiring pass, test whether the negative contactor closes and reports its state correctly using the specified procedure.
Common fixes
- Secure or clean a loose or corroded negative-contactor connector.
- Repair damaged wiring or a poor connection in the negative contactor circuit.
- Replace the negative contactor if its coil is open or it cannot close during the manufacturer's tests.
- Repair or replace the control module only if it fails the required circuit or feedback checks.
Can I keep driving?
Do not depend on the vehicle for normal driving if it cannot enter ready mode or electric drive is reduced; it may lose hybrid operation. Have a qualified hybrid technician diagnose the high-voltage contactor circuit.
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.