What it means
The control circuit of the belt-integrated starter/generator (BISG) belt tensioner reports a control circuit high condition. Belt tension cannot be modulated for assist/regen modes.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The BISG belt tensioner controls belt tension during engine starting, assist, and regenerative charging. The module monitors its control circuit and sets this code when the circuit signal is higher than expected, which can result from a short to battery voltage, an open actuator, or poor connector contact.
Common causes
Most likely first.
- Control wire shorted to B+
- Open tensioner actuator
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light or hybrid-system warning
- Reduced or unavailable start-stop, assist, or regenerative charging
How to diagnose it
- Check freeze-frame data and related hybrid-system codes for the operating conditions when the tensioner fault was detected.
- Inspect the tensioner connector for corrosion, loose terminals, or pins that are not seated fully.
- Trace the control wire for damage or contact with a battery-positive feed, paying attention to rubbed or repaired sections.
- Measure the tensioner control circuit for an unexpectedly high signal and check continuity with the actuator disconnected, following the manufacturer's procedure.
- Test the tensioner actuator for an open circuit using the manufacturer's specification.
Common fixes
- Repair control wiring shorted to battery voltage.
- Clean or repair corroded tensioner connector terminals.
- Restore secure terminal contact or repair damaged connector pins.
- Replace the BISG tensioner actuator if testing confirms it is open.
Can I keep driving?
The vehicle may disable start-stop, assist, or regenerative charging. Take care if power is limited, and stop if the belt slips, makes unusual noise, or a charging warning appears.
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.