Powertrain, generic · Fuel and air metering

P0197 Engine Oil Temperature Sensor A Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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. P0197 means the signal voltage is below its lower limit, so the module would read implausibly hot oil (around 145–150 °C) – practically always a signal wire shorted to ground or an internally shorted sensor. Ford sets it below 0.16–0.20 V for 5 s; GM below 25 Ω in 20 of 50 samples – without a warning light on the 2018 LT4, with two trips on the 2019 version, so MIL behaviour depends on the manufacturer and model year. A substitute value is used.

Likely causes

Signal wire chafed against ground or the engine block
Sensor shorted internally
Oil or water in the connector (leakage current)
Control module input faulty

Symptoms

  • Check engine light on (depending on manufacturer)
  • Oil temperature display at maximum or oil temperature warning
  • Fan running constantly or power reduction possible
  • Restricted cam timing (Ford)

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

P0195P0196P0198P0199P01BBP0117

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