P07CBTransmission Fluid Thermostat Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Many automatics have a thermostat in the fluid cooler circuit or a coolant-to-oil heat exchanger: a BMW patent describes a wax thermostat that bypasses the cooler until about 76 °C, a Ford patent a heat exchanger that warms transmission fluid from the coolant after a cold start. P07CB means this thermostat does not work as expected: fluid warms up too slowly (stuck open) or overheats (stuck closed). No manufacturer document available to us uses this code; GM checks fluid warm-up under the temperature sensor code P0711 (below 15 °C after the warm-up time, two trips). The check works like CARB's engine thermostat monitor (P0128). Slow warm-up raises consumption and delays converter lock-up; overheating ages fluid quickly.
- What you may notice
- Check engine or transmission warning lamp
- Converter clutch applies late, higher consumption
- Fluid overheating warning
- Likely causes
- LikelyTransmission fluid thermostat stuck open or closed
- PossibleFluid temperature sensor drifting
- PossibleCooler lines or heat exchanger blocked or leaking
- RareVery cold weather or short trips
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.