P0940 code meaning
Hydraulic Oil Temperature Sensor Circuit High
Powertrain system Generic code P09xx codes Check engine light
What P0940 means
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.
P0940 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0940
- Gearbox warning light on
- Shifts or clutch engagements feel rough once warm
Common causes of P0940
- Most likelyOpen signal or ground wire, or connector unplugged
- PossibleTemperature sensor open internally
- Less likelySignal wire shorted to a voltage source
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hydraulic oil temp sensorWiring harnessTCM
What each part of P0940 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9 | Area: transmission. |
| 40 | The exact fault in that area. |
What to do next
- Note P0940 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0940
What does P0940 mean?
P0940 means "Hydraulic Oil Temperature Sensor Circuit High". The hydraulic oil temperature sensor signal sits above its valid window. It is a generic code, so it means the same on every make.
Is it safe to drive with P0940?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0940 fail an emissions test?
Yes, it can. P0940 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0940 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P0940 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.