What it means
The ECM detects a low fault on the hybrid/ev battery pack voltage sense f circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Voltage-sense circuit F monitors a portion of the hybrid or EV battery pack. This code sets when the module sees the F signal below its expected electrical range, commonly because the signal is pulled toward ground, so it cannot rely on that voltage reading for battery control.
Common causes
Most likely first.
- Signal circuit short to ground
- Faulty voltage-sensing component
- Damaged wiring or poor connector contact
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 and related codes to confirm the fault conditions and check whether the low signal is isolated to circuit F.
- Compare live F-circuit data with other pack-sensing readings to confirm that F is abnormally low or absent.
- With the vehicle powered down according to the manufacturer's procedure, inspect accessible F-circuit wiring for chafing, pinching, exposed conductors, and connectors for corrosion or poor contact.
- Have a qualified hybrid technician test the F signal circuit for a short to ground and check its connections using the manufacturer's high-voltage safety procedure.
- If the signal wiring is not shorted to ground, test the F voltage-sensing component and module input to identify which is pulling the reading low.
Common fixes
- Reconnect or clean a loose or contaminated F-circuit connector.
- Repair F-circuit wiring shorted or damaged toward ground.
- Replace a confirmed faulty F voltage-sensing component.
- Repair or replace the module only if testing confirms a faulty F input.
Can I keep driving?
Avoid demanding acceleration and long trips because reduced power or charging limits may leave less usable electric range. If the vehicle enters limp mode or displays a high-voltage warning, stop safely and arrange qualified hybrid service.
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.