Damaged, chafed or corroded wiring to the pressure sensor or switch, causing an intermittent open or short; Poor connection at the sensor or transmission connector, such as loose terminals, corrosion or water ingress; Failing transmission fluid pressure sensor or switch giving a dropping-out signal; Contaminated, degraded or incorrect level of transmission fluid affecting the sensor reading or actual pressure; Genuine intermittent low or unstable hydraulic pressure from a worn pump, valve body or internal leak; Low system voltage or poor earth affecting sensor reference or signal; Fault within the transmission control unit.

P0844

Transmission Fluid Pressure Sensor/Switch A Circuit Intermittent.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
8: AreaTransmission
44: FaultThe specific fault in that area

What it means

P0844 is the generic code for an intermittent fault in the transmission fluid pressure sensor or switch 'A' circuit. The transmission control unit saw the signal drop out, spike or jump to implausible values from time to time rather than staying faulty. The exact sensor location and how it is used (for example line pressure or clutch circuit pressure) varies by model and gearbox.

Symptoms

Gearbox warning light or check engine light coming on and off
Occasional harsh, delayed or flared gear changes
Gearbox going into limp mode (fixed gear) at random
Erratic or unexpected shift timing
Torque converter lock-up not engaging at times
Fault clearing itself and then returning

Possible causes

Damaged, chafed or corroded wiring to the pressure sensor or switch, causing an intermittent open or shortlikely
Poor connection at the sensor or transmission connector, such as loose terminals, corrosion or water ingresslikely
Failing transmission fluid pressure sensor or switch giving a dropping-out signallikely
Contaminated, degraded or incorrect level of transmission fluid affecting the sensor reading or actual pressurepossible
Genuine intermittent low or unstable hydraulic pressure from a worn pump, valve body or internal leakpossible
Low system voltage or poor earth affecting sensor reference or signalpossible
Fault within the transmission control unitrare

How to diagnose

Read all stored and pending codes and note any related gearbox, voltage or communication faults
Review freeze frame data to see gear, temperature, speed and load when the fault set
Check transmission fluid level, condition and smell, following the manufacturer's procedure for that model
Inspect the sensor, harness and connectors for chafing, heat damage, fluid ingress, bent pins and corrosion
With the engine running, wiggle-test the harness and connector while watching live sensor data for dropouts
Check battery condition, charging voltage and the relevant earths
Measure the sensor reference, signal and earth circuits against the manufacturer's specification for that model
If the signal is stable and wiring is good, compare live readings with actual line pressure using a pressure test, where the model allows

How to fix

Repair or replace damaged wiring and ensure connectors are clean, dry and properly locked
Replace the pressure sensor or switch if its signal is erratic or out of specification
Correct the fluid level or change the fluid and filter if it is degraded, using the specified type
Repair charging or earth faults found during testing
Investigate and repair internal hydraulic faults, such as pump or valve body wear, if a real pressure problem is confirmed
Update or replace the control unit only if the manufacturer identifies an outdated calibration or confirmed unit fault

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but the gearbox may drop into limp mode or shift harshly without warning. Get it checked soon, as running with unstable pressure can cause further transmission wear.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.