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. P0848 means the B signal is too high. Allison sets it when switch 2 shows no pressure for over 0.175 s although valve S2 is applied, type A; GM's CVT when the second pulley sensor rises above 95 % duty cycle, a short to voltage or an open circuit. Mitsubishi treats it as a circuit fault to rule out first on its CVTs.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- Check engine or transmission warning lamp on
- Limp mode with a fixed gear, harsh or missing shifts
Most likely causes
- Signal or ground wire open, connector soaked with fluid
- Switch stuck open or sensor faulty
- Signal wire shorted to 5 V or battery voltage
- Too little pressure at the switch: low fluid level or sticking valve
- Control module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P0848 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 8: Transmission
- 48: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0848?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P0848?
The most common causes are: signal or ground wire open, connector soaked with fluid; switch stuck open or sensor faulty; signal wire shorted to 5 V or battery voltage.
Related codes
- P0845Transmission Fluid Pressure Sensor/Switch B Circuit
- P0846Transmission Fluid Pressure Sensor/Switch B Circuit Range/Performance
- P0847Transmission Fluid Pressure Sensor/Switch B Circuit Low
- P0843Transmission Fluid Pressure Sensor/Switch A Circuit High
Sources
- gsi.ext.gm.com: 23OBDG03A Part1
- gsi.ext.gm.com: 07 GRP15 Allison 1000
- static.nhtsa.gov: MC 10250860 0001
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.