P0198 code meaning
Engine Oil Temperature Sensor A Circuit High
Powertrain system Generic code P01xx codes Check engine light
What P0198 means
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. P0198 means the signal sits near the 5 V reference, so the module sees extremely cold oil (below −40 °C) – typically an unplugged connector, a broken wire, an open sensor element or a short to voltage. Ford sets it above 4.93–4.96 V for 5 s; GM above 450 kΩ, enabled only after 20 s of running or above −20 °C coolant so that real extreme cold is not mistaken for a fault; no MIL on the 2018 LT4, two trips in 2019. The module uses a substitute value and Ford disables variable cam timing.
P0198 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0198
- Check engine light on (depending on manufacturer)
- Oil temperature display stays at minimum or blank
- Restricted cam timing, possibly slightly less power
- Oil life monitor calculates with a substitute value
Common causes of P0198
- Most likelyConnector unplugged or pins corroded, signal or ground wire broken
- PossibleSensor element open
- Less likelySignal wire shorted to 5 V or battery voltage
- Less likelyControl module pull-up or input faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine oil temperature sensorSensor wiring
What each part of P0198 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 98 | The exact fault in that area. |
What to do next
- Note P0198 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0198
What does P0198 mean?
P0198 means "Engine Oil Temperature Sensor A Circuit High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0198?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0198 fail an emissions test?
Yes, it can. P0198 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0198 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0198 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.