Transmission Fluid Temperature Sensor "B" Circuit Intermittent

Possible causes

• CommonFailed temperature sensor - often part of the internal solenoid pack
• CommonCorroded or fluid-contaminated case connector
• CommonWiring damage between the transmission and the module
• PossibleInternal transmission harness failure
• PossibleLow fluid level leaving the sensor uncovered

What you might notice

• Harsh or delayed shifts, especially when cold
• Torque converter not locking up
• Higher fuel consumption
• Transmission temperature reading implausible
• Check engine light on

What to check, in order

1. Compare the reported fluid temperature with ambient on a vehicle that has stood overnight. A reading far from ambient on a cold car proves the sensor wrong without any dismantling.
2. Pull the transmission case connector and look for fluid inside it. Fluid wicking up the harness corrodes the pins and can reach and destroy the control module itself.
3. Check the wiring between the case connector and the module.
4. Check the fluid level and condition first. It is the cheapest check and it explains more transmission complaints than every electrical fault combined.
5. On many transmissions this sensor is part of the internal solenoid pack, so replacing it means dropping the pan. Confirm the fault properly before starting.