P2742 code meaning
Transmission Fluid Temperature Sensor B Circuit Low
Powertrain system Generic code P27xx codes Check engine light
What P2742 means
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.
P2742 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P2742
- 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
Common causes of P2742
- Most likelySignal lead of sensor B chafed through and touching ground
- PossibleSensor B shorted internally
- Less likelyControl unit with built-in sensor faulty (Mitsubishi TC-SST)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Trans fluid temp sensor bWiring harness
What each part of P2742 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 7 | Area: transmission. |
| 42 | The exact fault in that area. |
What to do next
- Note P2742 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 P2742
What does P2742 mean?
P2742 means "Transmission Fluid Temperature Sensor B Circuit Low". P2742 reports that the sensor B signal sits below its valid range, and how low is defined differs by maker. It is a generic code, so it means the same on every make.
Is it safe to drive with P2742?
Drive gently and only to a workshop. With P2742 the car can go into limp mode (reduced power) to protect itself.
Will P2742 fail an emissions test?
P2742 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P2742 to fix?
Difficulty: medium. A typical repair takes 0.5 to 6 hours of work. This is a job for a workshop.
Will P2742 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.