P01BB
Engine Oil Temperature Sensor B Circuit Low.
- Generic
- Powertrain
- Generic code
- Low severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 1
- AreaFuel and air metering
- BB
- FaultThe specific fault in that area
What it means
P01BB means the engine control unit has detected that the signal voltage from engine oil temperature sensor B is lower than the expected range. A low signal usually points to a short to ground or a sensor fault, which the control unit reads as an implausibly high temperature. The exact sensor location and the meaning of 'B' depend on the vehicle and engine.
Symptoms
- Engine warning light on
- Oil temperature gauge or reading showing a very high or implausible value
- Reduced performance or limp mode on some vehicles
- Cooling fan or oil cooling control behaving unexpectedly on some models
- Fault stored with no other obvious driveability change
Possible causes
- Faulty engine oil temperature sensor B (internal short)likely
- Signal wire chafed and shorted to earthlikely
- Damaged, contaminated or corroded connector or terminals, including oil ingresspossible
- Signal wire shorted to another earthed circuit or sensor earth faultpossible
- Wiring damage from heat or rubbing near the engine, sump or oil coolerpossible
- Fault in the engine control unitrare
How to diagnose
- Read all stored codes and freeze frame data, and note whether the fault is current or intermittent.
- Compare the live oil temperature reading with the coolant temperature on a cold engine; they should be close.
- Visually inspect the sensor, connector and wiring for chafing, heat damage, oil contamination and corrosion.
- Unplug the sensor with the ignition on and check the live reading; a value that moves to the sensor's open-circuit reading suggests the sensor is at fault.
- Measure the sensor resistance and compare it with the manufacturer's temperature specification.
- Check the signal wire for a short to earth and the sensor reference and earth circuits for continuity, using the wiring diagram for the model.
- Wiggle test the harness with the engine running to find intermittent faults.
- Confirm which sensor is 'B' for this engine using manufacturer data before replacing parts.
How to fix
- Replace the oil temperature sensor if its resistance or signal is out of specification.
- Repair or replace the damaged wiring where the signal circuit is shorted to earth.
- Clean, repair or replace the connector and terminals, and fix any source of oil ingress.
- Secure and reroute the harness away from heat and sharp edges.
- Clear the code after repair and road test to confirm it does not return; consider control unit checks only after wiring and sensor are proven good.
Can I keep driving?
Low severity
The car can usually be driven short term, but book it in soon as the control unit may be using a default temperature value. If the oil temperature warning shows or the car enters limp mode, limit driving and have it checked promptly.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.