P2742Transmission Fluid Temperature Sensor B Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2742 reports that the sensor B signal sits below its valid range, and how low is defined differs by maker. GM's 2023/24 dual-clutch TCM treats a cooler temperature sensor value under 200 mV, with hysteresis, for at least 500 ms as too low, Type B; for the usual NTC thermistor that equals an extremely hot reading or a signal wire shorted to ground. Ford's TR9070 lists P2742 as the out-of-window-low test of its cooler-out sensor. Mitsubishi's 2009 Twin Clutch SST instead relates Low to the computed temperature: −40 °C or colder for 400 ms, naming the transaxle-integrated unit as suspect. Real overheating with a sound sensor belongs to P273F. Afterwards the module ignores sensor B and uses a substitute.
- What you may notice
- Warning lamp after two trips on GM
- Scan tool shows sensor B extremely hot (GM, Ford) or extremely cold (Mitsubishi)
- Protective strategy with substitute temperature
- Likely causes
- LikelySignal lead of sensor B chafed through and touching ground
- PossibleSensor B shorted internally
- RareControl unit with built-in sensor faulty (Mitsubishi TC-SST)
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.