P0199Engine Oil Temperature Sensor A Circuit Intermittent/Erratic
- 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 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.
- What you may notice
- Check engine light or only a stored code
- Oil temperature reading jumps
- Occasionally restricted cam timing
- Likely causes
- LikelyLoose contact or corroded pins at the sensor connector
- PossibleHarness chafing intermittently (engine movement)
- PossibleSensor with internal hairline crack
- RareControl module ground connection
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · 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.