Powertrain, generic (extended)

P2740 Transmission Fluid Temperature Sensor B Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modeNo

P2740 is the umbrella circuit code for a second transmission fluid temperature sensor, labelled B. The control module supplies the thermistor with a reference voltage and flags an electrical fault when the returned signal leaves its plausible window, without separating short from open. Where B is documented, it sits outside the sump: Ford's TR9070 dual-clutch gearbox and a GM dual-clutch module of 2023/24 both use it for the fluid leaving the cooler, but report electrical faults through the split codes P2742/P2743 rather than P2740. No manufacturer publishes P2740 itself. Without a valid B value the module relies on sensor A or a default, so cooler control and hot-fluid protection get coarser; shifting usually remains normal.

Likely causes

Loose, corroded or damaged connector or lead to sensor B
Sensor B thermistor open or shorted internally
Faulty input stage in the transmission control module

Symptoms

  • Warning lamp or transmission message
  • Fluid temperature B shows an implausible fixed value on the scan tool
  • Cooler or hot-fluid protection works with a substitute value

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

trans fluid temp sensor bwiring harness

Related codes

P2741P2742P2743P2744P0710

References: law.cornell.edu, gsi.ext.gm.com, fordservicecontent.com.