Powertrain, generic · Transmission

P0939 Hydraulic Oil Temperature Sensor Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

The hydraulic oil temperature sensor signal sits below its valid window. With the usual NTC thermistor, a low voltage corresponds to an implausibly hot reading and typically comes from a signal wire shorted to ground or a sensor shorted internally. Ferrari uses P0939 on its DCT for the radiator outlet and gearbox inlet oil temperature sensor, described as signal too low and read in the NCR gearbox ECU. CARB requires out-of-range checks on transmission sensors. P0940 is the high counterpart, P0937 the general circuit fault, P0938 plausibility and P0941 intermittent. Because the module believes the oil is very hot, it may reduce torque, change shift strategy or show an overheat warning.

Likely causes

Sensor signal wire shorted to ground
Temperature sensor shorted internally
Control module input fault

Symptoms

  • Gearbox warning or overheat message
  • Reduced performance or altered shift behaviour

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–500
Time0.5–2 h

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

Parts involved

hydraulic oil temp sensorwiring harnesstcm

Related codes

P0937P0938P0940P0941P0712

References: law.cornell.edu, static.nhtsa.gov.