P01BD: Engine Oil Temperature Sensor B Circuit Intermittent/Erratic

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. P01BD covers brief or erratic signal faults of sensor B, the counterpart of P0199 – typically a loose contact or a harness chafing as the engine moves. 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 or only a stored code
• Jumping oil temperature values
• Usually no driving symptoms

Most likely causes

• Loose contact or corrosion at the sensor B connector
• Harness chafing intermittently
• Sensor B with internal hairline crack

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. Gently move the wiring with the engine running and watch whether the reading changes.
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: medium
• It affects emissions.

What each character of P01BD means

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

Frequently asked questions

Can I keep driving with code P01BD?

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 P01BD?

The most common causes are: loose contact or corrosion at the sensor B connector; harness chafing intermittently; sensor B with internal hairline crack.

Related codes

• P01B9Engine Oil Temperature Sensor B Circuit
• P01BAEngine Oil Temperature Sensor B Range/Performance
• P01BBEngine Oil Temperature Sensor B Circuit Low
• P01BCEngine Oil Temperature Sensor B Circuit High
• P0199Engine Oil Temperature Sensor A Circuit Intermittent/Erratic

Sources

• law.cornell.edu: 13 CCR 1968.2
• saabwisonline.com: temperature sensor engine oil

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.