Powertrain, generic · Fuel and air metering

P0198 Engine Oil Temperature Sensor A Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Connector unplugged or pins corroded, signal or ground wire broken
Sensor element open
Signal wire shorted to 5 V or battery voltage
Control module pull-up or input faulty

Symptoms

  • 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

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–200
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine oil temperature sensorsensor wiring

Related codes

P0195P0196P0197P0199P01BCP0118

References: law.cornell.edu, fordservicecontent.com, gsi.ext.gm.com, gsi.ext.gm.com.