The engine oil temperature sensor A 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. P0199 covers brief or erratic signal faults: the value jumps faster than oil temperature can physically change, or a circuit fault appears only momentarily – typically a loose contact. No manufacturer document with thresholds for P0199 was found; GM and Ford catch short faults with counting windows under P0197/P0198. The description rests on CARB's circuit monitoring requirement and component information.
High severity. Can I keep driving?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.
Symptoms
- Check engine light or only a stored code
- Oil temperature reading jumps
- Occasionally restricted cam timing
Most likely causes
- Loose contact or corroded pins at the sensor connector
- Harness chafing intermittently (engine movement)
- Sensor with internal hairline crack
- Control module ground connection
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0199 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 99: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0199?
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 P0199?
The most common causes are: loose contact or corroded pins at the sensor connector; harness chafing intermittently (engine movement); sensor with internal hairline crack.
Related codes
- P0195Engine Oil Temperature Sensor A Circuit
- P0196Engine Oil Temperature Sensor A Range/Performance
- P0197Engine Oil Temperature Sensor A Circuit Low
- P0198Engine Oil Temperature Sensor A Circuit High
- P01BDEngine Oil Temperature Sensor B Circuit Intermittent/Erratic
Sources
- law.cornell.edu: 13 CCR 1968.2
- fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
- 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.