Powertrain, generic · Transmission

P0848 Transmission Fluid Pressure Sensor/Switch B Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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

Symptoms

  • Check engine or transmission warning lamp on
  • Limp mode with a fixed gear, harsh or missing shifts

Repair estimate

DifficultyHardWorkshop job
Parts and labour€120–900
Time1–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

transmission fluid pressure sensortransmission valve bodytransmission wiringtransmission control module

Related codes

P0845P0846P0847P0843

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.