What it means
The control module detects a high 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 an electrical-isolation signal to the control module. This high-circuit code sets when the module sees a signal above its expected range, often because of an open circuit or signal-wire fault rather than a low signal.
Common causes
Most likely first.
- Open circuit or signal wire fault
- Sensor 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 high and identify accompanying circuit faults.
- Check live sensor data to confirm whether the high reading is present now or occurred only intermittently.
- With the vehicle safely powered down as instructed by the manufacturer, inspect the isolation sensor connector and signal wiring for an unplugged connection, broken wire, corrosion, or poor terminal contact.
- Test the signal circuit for opens and poor connections using the manufacturer's procedure.
- Have a qualified hybrid technician test the isolation sensor against the manufacturer's specification without probing high-voltage terminals.
- If the wiring and sensor pass, check the control module input and grounds following the specified diagnostic steps.
Common fixes
- Reconnect and secure a loose isolation-sensor connector.
- Repair an open, damaged, or poorly connected signal wire.
- Replace the isolation sensor if it fails the manufacturer's tests with intact wiring.
- Repair or replace the control module only if its input checks fail.
Can I keep driving?
If a hybrid-system warning appears, avoid relying on electric drive until the fault is diagnosed; the vehicle may limit or disable hybrid operation. Keep clear of high-voltage components and use 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.