What it means
The control circuit of the HV battery negative contactor reports a control circuit/open condition. HV main switching 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
The negative contactor is the high-voltage battery switch that connects the pack's negative side to the vehicle's high-voltage system. P0ADD sets when the module detects an open condition in the negative contactor control circuit, preventing reliable operation of that switch.
Common causes
Most likely first.
- Open in coil control wire
- Open contactor coil
- Pin pushed back out of connector body
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Read freeze-frame data and related hybrid codes to identify whether the fault occurred during startup, driving, or charging.
- Follow the vehicle's high-voltage safety procedures before inspecting the negative contactor control connector or wiring.
- Inspect the accessible harness and connector for a loose plug, backed-out pin, corrosion, or visible wire damage.
- Test the negative contactor coil and control wiring for continuity using the manufacturer's procedure.
- If continuity is present, check the control output and circuit behavior using the manufacturer's diagnostic process.
Common fixes
- Reconnect and secure a loose negative contactor control connector.
- Repair an open wire or backed-out terminal in the control circuit.
- Replace the negative contactor if its coil has an open circuit.
- Repair the control circuit or module connection identified by testing.
Can I keep driving?
If the vehicle will not enter READY mode, loses propulsion, or shows a high-voltage system warning, stop safely and arrange qualified hybrid service; the negative contactor may not connect the pack reliably. Do not open or probe high-voltage components yourself.
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.