P01BC
Engine Oil Temperature Sensor B Circuit High.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 1
- AreaFuel and air metering
- BC
- FaultThe specific fault in that area
What it means
P01BC means the engine control unit saw the signal from engine oil temperature sensor B above its expected voltage range. On a typical thermistor-type sensor this points to an open circuit, a short to voltage, or a failed sensor, which makes the oil look extremely cold. Which sensor is 'B' and where it sits depends on the vehicle and engine.
Symptoms
- Engine warning light on
- Oil temperature gauge or display reads implausibly low, shows no reading or shows a fault
- Reduced performance or a limp-mode style strategy on some models
- Cooling fan or oil-temperature-dependent functions behaving oddly on some models
- Slightly higher fuel consumption if the control unit assumes the oil is cold
- Possible extra stored codes for other oil or coolant temperature sensors
Possible causes
- Faulty engine oil temperature sensor B (internal open circuit)likely
- Damaged, corroded or loose sensor connector or terminalslikely
- Open circuit in the signal or ground wire, for example from chafing or heat damagelikely
- Signal wire shorted to a voltage supply or to another circuitpossible
- Oil leak or contamination getting into the sensor connector or wiring loompossible
- Fault inside the engine control unit or its sensor reference supplyrare
- Outdated control unit software on certain models, where the manufacturer has issued a fixrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting oil temperature, coolant temperature and engine run time when the code set.
- Compare live oil temperature with coolant temperature on a warm engine; a stuck very low or implausible value suggests an open circuit or sensor fault.
- Check which sensor is 'B' for this model and engine using manufacturer information, then find its location.
- Inspect the sensor, connector and wiring for oil contamination, chafing, heat damage, corrosion and bent or pushed-back pins.
- With the connector unplugged, check the reference voltage and ground at the harness side against the manufacturer's specification.
- Test the sensor resistance at a known temperature and compare it with the specification for that sensor.
- Check the signal wire for continuity to the control unit and for shorts to voltage or ground.
- If wiring and sensor are good, check for applicable software updates and have the control unit tested.
How to fix
- Replace the engine oil temperature sensor B if its resistance is out of specification, using a sensor that is correct for the engine.
- Clean or repair the connector, or replace damaged terminals, and fit a new connector where needed.
- Repair or replace open or damaged wiring, and secure the loom away from heat and sharp edges.
- Fix any short to voltage by repairing the damaged insulation or the affected circuit.
- Rectify any oil leak that is contaminating the connector or loom, and replace parts that are oil-soaked.
- Update the control unit software only if the manufacturer lists it as a fix for this fault, or repair or replace the control unit if testing proves it faulty.
Can I keep driving?
Medium severity
The car can usually be driven for a short time, but book it in soon because the control unit may be using a default oil temperature value. Stop and investigate if the oil pressure warning lights, the engine overheats, or the car goes into limp mode.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.