P0846Transmission Fluid Pressure Sensor/Switch B Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Transmission fluid pressure sensor/switch A and B are inputs inside the automatic gearbox. A switch only reports pressure present or absent, a sensor reports a value. The letter is the maker's choice: Allison 1000 uses A and B for the switches on shift valves S1 and S2, GM's CVT for the primary and secondary pulley sensors, GM's 2025 8-speed A for the lube pressure sensor; Ford reports pressure faults under its solenoid codes instead. P0846 is the plausibility fault of B. GM's CVT uses the same test as for A on its second pulley: pressure off target by 500 or 1500 kPa plus a ratio error above 0.2 for about 6 s, line pressure above 600 kPa, over 35 km/h, type A. Allison sets it when switch 2 stays without pressure 5 s after valve S2 is applied. On the Corvette dual clutch a sticking valve is the usual cause.
- What you may notice
- Check engine or transmission warning lamp on
- Slipping or shift shock
- CVT: ratio and power limited
- Likely causes
- LikelyDirty or sticking valve, worn valve body
- LikelyPressure sensor or switch drifting or sticking
- PossibleFluid level low, fluid aged or filter clogged
- PossibleMechanical damage: thrust washer, CVT belt or pulley, pump
- RareControl module software
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.