Powertrain, generic · Transmission

P0841 Transmission Fluid Pressure Sensor/Switch A Circuit Range/Performance

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. P0841 means the signal is electrically fine but does not match the commanded state. GM's CVT sets it when pulley pressure misses its target by more than 500 kPa steady or 1500 kPa transient while the ratio is off by over 0.2 for about 6 s, type A. GM's 8-speed checks the lube sensor rises above 40 kPa after start-up; Mitsubishi's CVT sets it at 0.675 MPa deviation for 5 s.

Likely causes

Dirty or sticking valve, worn valve body
Pressure sensor or switch drifting or sticking
Fluid level low, fluid aged or filter clogged
Mechanical damage: thrust washer, CVT belt or pulley, pump
Control module software

Symptoms

  • Check engine or transmission warning lamp on
  • Shift shock, slipping or delayed engagement
  • CVT: ratio and power limited

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–2,500
Time1–8 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

P0840P0842P0843P0846P0868P0776

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