Powertrain, generic · Transmission

P0844 Transmission Fluid Pressure Sensor/Switch A Circuit Intermittent

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. P0844 reports short dropouts or jumps of the signal without a lasting low or high. GM documents it in bulletin 21-NA-033 for the Corvette C8 dual clutch, together with P0841, P0846 and P0849: often a sticking valve is the cause, so the valve body is flushed and a fast learn run; if the code returns alone, the circuit is checked. Thresholds are not published.

Likely causes

Loose contact or corrosion at the gearbox connector or control unit
Dirt in valve or sensor causing signal jumps
Sensor faulty internally
Chafed spot in the harness

Symptoms

  • Warning lamp coming and going
  • Occasional shift shocks
  • Brief limp mode

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–800
Time1–4 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

P0840P0841P0842P0843P0849

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.