What it means
The control module detects a low signal in the hybrid battery voltage isolation sensor circuit.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The hybrid battery voltage isolation sensor sends a signal to the control module about electrical isolation in the high-voltage system. This low-circuit code sets when the module sees a signal below its expected range, which can result from a signal wire shorted to ground or a sensor or circuit fault.
Common causes
Most likely first.
- Signal wire shorted to ground
- Sensor or circuit fault
- Wiring or connector fault
Symptoms
- Hybrid system warning light
How to diagnose it
- Read freeze-frame data and related hybrid codes to establish when the isolation-sensor signal went low and whether other circuit faults are present.
- Check live sensor data and circuit status to confirm the low reading is current and not a stored intermittent event.
- With the vehicle powered down as specified by the manufacturer, inspect the isolation sensor signal wiring, connector, and ground for damage, moisture, corrosion, or pin contact with ground.
- Test the signal wire for a short to ground and check the circuit connections using the manufacturer's procedure.
- Have a qualified hybrid technician test the isolation sensor output against the manufacturer's specification, without probing high-voltage terminals.
- If the signal wire and sensor pass, check the control module input and its grounds as specified.
Common fixes
- Repair a signal wire chafed or shorted to ground.
- Clean and secure a corroded or loose isolation-sensor connector.
- Replace the isolation sensor if its output remains below specification with a sound circuit.
- Repair or replace the control module only if its input checks fail.
Can I keep driving?
Limit driving if the hybrid warning coincides with reduced operation, and stop if the vehicle reports a high-voltage safety fault. The system may disable hybrid drive; arrange diagnosis by a qualified hybrid technician.
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.