P01BB: Engine Oil Temperature Sensor B Circuit Low

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.

Symptoms

• Check engine light on (depending on manufacturer)
• Oil temperature warning or maximum reading possible
• Fan possibly running constantly

Most likely causes

• Signal wire of sensor B shorted to ground
• Sensor B shorted internally
• Moisture or oil in the connector
• Control module

What to check, in order

Start with the simplest. You can tick off each step.

1. Stop and check the level with the dipstick or the car's menu
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Check for leaks and inspect the sensor's connector
4. Measure the actual pressure with a gauge
5. Check the valve or pump according to the manual

Good to know

• Repair difficulty: easy
• It affects emissions.

What each character of P01BB means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 1: Air and fuel
• BB: Specific fault in that system

Frequently asked questions

Can I keep driving with code P01BB?

If the red oil warning light comes on, stop the car in a safe place and turn off the engine. Do not continue until you have confirmed the level and pressure.

What causes code P01BB?

The most common causes are: signal wire of sensor B shorted to ground; sensor B shorted internally; moisture or oil in the connector.

Related codes

• P01B9Engine Oil Temperature Sensor B Circuit
• P01BAEngine Oil Temperature Sensor B Range/Performance
• P01BCEngine Oil Temperature Sensor B Circuit High
• P01BDEngine Oil Temperature Sensor B Circuit Intermittent/Erratic
• P0197Engine Oil Temperature Sensor A Circuit Low

Sources

• law.cornell.edu: 13 CCR 1968.2
• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
• en.wikipedia.org: Thermistor

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.