P0940
Hydraulic Oil Temperature Sensor Circuit High
Transmission / hydraulic control
Generic OBD-II
Medium
What it means
P0940 means the transmission control module reads a higher-than-expected voltage from the hydraulic oil (transmission fluid) temperature sensor circuit. Because the module uses fluid temperature to adjust shift timing, a bad reading can make it shift cautiously or enter a protective mode. The engine still starts and runs — this is a transmission temperature-sensor fault, not an engine problem.
Medium
Can I keep driving? Usually drivable, but the transmission may adopt cautious shift timing or limp mode — have it checked soon.
Common symptoms
What you'll notice
- Check-engine light on
- Altered or cautious shift timing
- Transmission may enter a fail-safe (limp) mode
- Inaccurate transmission temperature readings
Common causes
Most likely first
- Faulty hydraulic oil temperature sensorLikely
- Short to voltage or high resistance in the sensor circuitCommon
- Wiring or connector problems in the sensor circuitCommon
- Failed transmission control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and inspect the hydraulic oil temperature sensor connector and wiring for damage or corrosion.
- Check the sensor circuit for a short to voltage or high resistance with a multimeter.
- Confirm the sensor has a proper voltage supply and clean ground.
- Replace the hydraulic oil temperature sensor if it reads out of range with wiring confirmed good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0940?+
Short trips are usually fine, but the transmission may shift conservatively to protect itself, so get it diagnosed soon.
Can I just clear P0940?+
It will clear, but the high-circuit reading returns until the sensor or wiring is repaired.
Related codes
Often seen with P0940
Read & clear P0940 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX