P0844: Transmission Fluid Pressure Sensor/Switch A Circuit Intermittent

What does P0844 mean?

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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

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

Common causes

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

Likelihood is a general estimate across vehicles; your make and model may differ.