What it means
The HV battery pack cooling fan 1 sense circuit reports a sense range/performance fault. Fan speed feedback is unreliable.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The hybrid battery cooling fan moves air through the high-voltage battery pack, while its sense circuit reports fan 1 speed to the control module. P0BC8 sets when that feedback is present but falls outside the expected range or does not match expected fan performance, such as from signal drift, a high-resistance contact, or an aged sensing element.
Common causes
Most likely first.
- Feedback signal drifted
- High-resistance contact
- Sensor element aged beyond calibration window
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
- Save freeze-frame data and compare commanded fan 1 speed with live feedback, if available, to establish when the reported speed becomes implausible.
- With the vehicle powered down as specified by service information, inspect the fan 1 sense connector and harness for corrosion, loose terminals, or damage that can add resistance.
- Check that fan 1 turns freely and that its air path is not obstructed, since poor airflow can coincide with abnormal fan performance.
- Use the manufacturer's wiring information to check the sense circuit for excessive resistance or an unstable connection.
- If the wiring and fan operation check out, test the fan speed feedback element against the manufacturer's specification for drift or aging.
Common fixes
- Clean and secure high-resistance or loose fan 1 sense connector terminals.
- Clear debris from the fan air path if it is obstructed.
- Repair damaged or high-resistance wiring in the fan 1 feedback circuit.
- Replace the fan or feedback element if it fails the specified performance test.
Can I keep driving?
Avoid heavy driving and charging until fan 1 feedback is reliable, particularly if the vehicle limits power or shows a hybrid warning. Incorrect speed feedback can lead to protective limits and reduced battery cooling.
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.