P01BBEngine Oil Temperature Sensor B Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The engine oil temperature sensor B is an NTC thermistor fed with 5 V through a resistor: the hotter the oil, the lower the signal voltage. The engine module uses the oil temperature for variable cam timing (Ford disables it with cold oil or a sensor fault), engine protection and the oil life monitor; many engines have no such sensor and use a calculated oil temperature instead. Sensor B is a second oil temperature sensor whose position is defined by the manufacturer. P01BB means the signal of sensor B is below its lower limit – the NTC would report very hot oil; typically a signal wire shorted to ground or an internally shorted sensor. Thresholds are presumably similar to sensor A (Ford about 0.16–0.20 V, GM below 25 Ω) but are not documented for B. No manufacturer document using the B-sensor codes was found, so it is unclear who fits a sensor B; the description follows sensor A and CARB's circuit monitoring requirement.
- What you may notice
- Check engine light on (depending on manufacturer)
- Oil temperature warning or maximum reading possible
- Fan possibly running constantly
- Likely causes
- LikelySignal wire of sensor B shorted to ground
- PossibleSensor B shorted internally
- PossibleMoisture or oil in the connector
- RareControl module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.