What it means
The cell thickness sensor circuit for hybrid/EV battery pack A has a signal above the expected range. This indicates a circuit or sensor signal fault; it does not by itself indicate a cell voltage problem.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The BMS monitors the signal circuit for the cell thickness sensor in hybrid/EV battery pack A. This code sets when that signal is higher than the expected range, which can result from a short to battery voltage, an open sensor, or poor connector contact; it does not mean the cell voltage is high.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open sensor
- Connector pins corroded - high contact resistance
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
- Record freeze-frame data and view pack A thickness sensor live data to confirm the high signal and check whether it is fixed or changes.
- Check for other pack A sensor circuit codes and compare available pack A and pack B readings to see whether the fault is isolated to this circuit.
- With the vehicle made safe according to the manufacturer's procedure, inspect pack A sensor wiring for a short to power and check connectors for corrosion or poor pin contact.
- Test the pack A sensor circuit for opens and unintended connection to battery voltage, following the manufacturer's wiring information.
- Measure the sensor output and circuit continuity against the manufacturer's specifications to determine whether the sensor or its wiring is at fault.
Common fixes
- Clean and secure corroded or loose pack A sensor connector pins.
- Repair pack A sensor wiring shorted to battery voltage or an open circuit.
- Replace the pack A thickness sensor if it remains open or produces an out-of-range high signal.
- Recheck the BMS readings after repair and perform any required manufacturer-specified calibration.
Can I keep driving?
A high pack A sensor signal can make the BMS limit propulsion or charging, so avoid heavy acceleration and plan only a short trip to service if the vehicle remains controllable. Stop if a battery warning escalates, power drops sharply, or the pack becomes unusually hot.
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.