P2743: Transmission Fluid Temperature Sensor B Circuit High

P2743 is the counterpart of P2742: the sensor B signal is above its valid range. In GM's 2023/24 dual-clutch TCM the cooler temperature sensor must exceed 4745 mV for 500 ms, Type B; with an NTC thermistor fed from 5 V that points to a broken wire, an unplugged connector or a short to supply voltage, and the reading looks extremely cold. Ford uses P2743 as the out-of-window-high check of the TR9070 cooler-out sensor. Mitsubishi's 2009 Lancer Twin Clutch SST again reasons in temperature: 150 °C or more for 400 ms sets the code, and it advises checking the CAN bus first because bus faults can produce a false entry. Without B the module can no longer judge the cooler outflow and falls back on sensor A.

Symptoms

• Warning lamp or transmission message
• Scan tool shows sensor B extremely cold (GM, Ford) or extremely hot (Mitsubishi)
• Cooler control falls back on sensor A

Most likely causes

• Open circuit – broken lead or unplugged connector at sensor B
• Signal lead shorted to a voltage source
• CAN fault or control unit with built-in sensor (Mitsubishi TC-SST)

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the fluid level and condition
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Read the input and output speed in live data
4. Check the connector and wiring
5. Check for other related engine codes
6. Consult the manufacturer's procedure for the transmission

Good to know

• Repair difficulty: medium
• It can trigger limp mode.

What each character of P2743 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 7: Transmission
• 43: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2743?

Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.

What causes code P2743?

The most common causes are: open circuit – broken lead or unplugged connector at sensor B; signal lead shorted to a voltage source; cAN fault or control unit with built-in sensor (Mitsubishi TC-SST).

Related codes

• P2740Transmission Fluid Temperature Sensor B Circuit
• P2741Transmission Fluid Temperature Sensor B Circuit Range/Performance
• P2742Transmission Fluid Temperature Sensor B Circuit Low
• P2744Transmission Fluid Temperature Sensor B Circuit Intermittent
• P0713Transmission Fluid Temperature Sensor A Circuit High

Sources

• gsi.ext.gm.com: 24OBDG07
• mitsubishitechinfo.com: M122502270035600USA
• fordservicecontent.com: OBDSM2400OUTPUT 16Jul2024 WSM final V2 MCS7001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.