Powertrain, generic · Transmission

P0938 Hydraulic Oil Temperature Sensor Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

By J2012 wording the hydraulic oil temperature reading is electrically valid but implausible, for example frozen, rising too slowly after a cold start or disagreeing with other temperature values. Ferrari uses P0938 on its DCT for the radiator outlet and gearbox inlet oil temperature sensor, but describes it in its bulletin as no signal, an electrical fault rather than a plausibility check; the code is read in the NCR gearbox ECU. CARB asks for rationality checks on temperature inputs. P0937 is the general circuit fault, P0939 and P0940 the low and high faults, P0941 intermittent. A wrong temperature value leads to poorly matched clutch and shift pressures and may limit the cooling strategy.

Likely causes

Temperature sensor drifting or reacting sluggishly
Signal lost through connector or wiring fault (as in Ferrari's no-signal case)
Real temperature anomaly from a cooler or thermostat fault

Symptoms

  • Gearbox warning light on
  • Shift and clutch quality inconsistent with operating temperature

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time0.5–2.5 h

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

Parts involved

hydraulic oil temp sensorwiring harnesstcm

Related codes

P0937P0939P0940P0941P0711

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