Powertrain, generic · Transmission

P0940 Hydraulic Oil Temperature Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The hydraulic oil temperature sensor signal sits above its valid window. With an NTC thermistor this matches an extremely cold reading, typically from an open circuit, an unplugged connector, a broken ground or a short to a voltage source. Ferrari uses P0940 on its DCT for the radiator outlet and gearbox inlet oil temperature sensor, described as an electrical fault with signal too high, read in the NCR gearbox ECU. CARB requires out-of-range checks on transmission sensors. P0939 is the low counterpart, P0937 the general circuit fault, P0938 plausibility and P0941 intermittent. With a substitute value the gearbox works on, but clutch and shift pressures are no longer matched to the real oil temperature.

Likely causes

Open signal or ground wire, or connector unplugged
Temperature sensor open internally
Signal wire shorted to a voltage source

Symptoms

  • Gearbox warning light on
  • Shifts or clutch engagements feel rough once warm

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

P0937P0938P0939P0941P0713

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