P2742
Transmission Fluid Temperature Sensor B Circuit Low
Transmission (temperature sensor)
Generic OBD-II
Low
What it means
P2742 means the TCM sees a low-voltage (usually short-to-ground) signal from transmission fluid temperature sensor B. The transmission uses fluid temperature to schedule shifts and converter lockup, so a bad reading can change shift feel or delay lockup. It's typically a sensor or wiring fault — the car remains drivable while you sort it out.
Low
Can I keep driving? Drivable — the main effect is altered shift feel and delayed converter lockup until repaired.
Common symptoms
What you'll notice
- Check-engine light on with the code stored
- Altered or firmer shift behavior
- Delayed torque converter lockup
- Slightly reduced fuel economy
- Limp mode in some cases
Common causes
Most likely first
- Short to ground in the temperature sensor B wiringLikely
- Faulty transmission fluid temperature sensor BCommon
- Corroded or shorted connector at the sensorCommon
- TCM internal faultLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and compare the temperature PID with actual.
- Inspect the sensor connector and wiring for a short to ground.
- Measure the sensor's resistance against the temperature table.
- Replace the sensor if it reads out of range.
- Verify the reading is realistic, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2742?+
Yes, generally. The transmission uses a default temperature value, so shift feel and converter lockup may change slightly, but the car drives normally otherwise.
Can I just clear P2742?+
It returns until the sensor or its wiring is repaired. Clearing won't restore an accurate temperature reading.
Related codes
Often seen with P2742
Read & clear P2742 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