What it means
The ECM detects a circuit fault on the hybrid/ev battery temperature sensor b 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
Battery temperature sensor B reports the temperature at its monitored point in the hybrid/EV battery pack, and the control module uses that reading to manage battery operation. P0AC5 sets when the sensor B circuit has an electrical fault, so the reported temperature may not be reliable.
Common causes
Most likely first.
- Fault in temperature-sensor wiring or connector
- Failed battery temperature sensor B
- Fault in the battery control module
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 scan the hybrid modules for related temperature-sensor or battery-control codes.
- Compare sensor B live data with other battery temperature readings and the vehicle's recent operating conditions; look for a missing or implausible value.
- Inspect temperature sensor B's connector and harness for damage, corrosion, poor seating, or contact with nearby components.
- Test sensor B's signal, ground, and reference circuits for opens, shorts, or poor connections using the manufacturer's wiring information.
- If the circuit checks out, test battery temperature sensor B and the battery control module input using the manufacturer's diagnostic procedure.
Common fixes
- Secure the sensor B connector and repair damaged or corroded wiring.
- Restore a poor reference or ground connection in the sensor B circuit.
- Replace battery temperature sensor B if its output fails the manufacturer's test.
- Repair or replace the battery control module only if testing confirms its input is faulty.
Can I keep driving?
Avoid heavy loads and long trips while the hybrid warning is on or power is limited, since the system may restrict charging or battery assistance when it cannot trust sensor B's temperature. Stop if the battery or hybrid system displays an overheating warning.
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.