P0849Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent
- 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. P0849 reports short dropouts of the B signal. GM bulletin 21-NA-033 for the Corvette C8 dual clutch lists it with P0841, P0844 and P0846: first the valves are cleaned and the clutches relearned, and only if the code comes back on its own is the circuit traced. Like the A counterpart P0844 it has no published thresholds.
- What you may notice
- Warning lamp coming and going
- Occasional shift shocks
- Brief limp mode
- Likely causes
- LikelyLoose contact or corrosion at the gearbox connector or control unit
- PossibleDirt in valve or sensor causing signal jumps
- PossibleSensor faulty internally
- RareChafed spot in the harness
- 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: €100 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.