Damaged, chafed, or corroded wiring in the sensor/switch 'A' circuit, often near connectors or where the harness bends; A failing transmission fluid pressure sensor/switch 'A' itself, causing an intermittent open or short; Loose or contaminated electrical connector at the sensor or at the TCM, leading to poor contact; Low or degraded transmission fluid that causes pressure fluctuations the sensor interprets as circuit faults; Internal transmission mechanical wear (e.g., valve body or pump issues) that produces erratic pressure readings; A faulty TCM or a software glitch that misinterprets momentary signal dropouts as a circuit fault

DTC codes / P08xx · Transmission / P0844

P0844Transmission Fluid Pressure Sensor/Switch 'A' Circuit Intermittent

P0844 indicates that the transmission control module (TCM) has detected an intermittent fault in the electrical circuit for Transmission Fluid Pressure Sensor/Switch 'A', which is responsible for monitoring hydraulic pressure inside the transmission. The circuit's signal momentarily drops out or becomes erratic, but the fault is not continuously present, so the TCM cannot rely on the pressure reading for precise shift control.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaTransmission

Symptoms you may notice

Illumination of the check engine light or transmission warning light, often with no other noticeable symptoms
Harsh or delayed gear shifts, especially when the transmission is cold or under light throttle
The transmission may intermittently slip or fail to engage a gear, then recover
Erratic shift points or the transmission entering limp mode (stuck in one gear) on occasion
A stored code P0844 may be the only sign, with no drivability complaints at all

Common causes, most likely first

Damaged, chafed, or corroded wiring in the sensor/switch 'A' circuit, often near connectors or where the harness bends
A failing transmission fluid pressure sensor/switch 'A' itself, causing an intermittent open or short
Loose or contaminated electrical connector at the sensor or at the TCM, leading to poor contact
Low or degraded transmission fluid that causes pressure fluctuations the sensor interprets as circuit faults
Internal transmission mechanical wear (e.g., valve body or pump issues) that produces erratic pressure readings
A faulty TCM or a software glitch that misinterprets momentary signal dropouts as a circuit fault

How to diagnose and fix it

Check the transmission fluid level and condition; top off or replace fluid if it is low or burnt, as this is the cheapest first step
Inspect the sensor/switch 'A' connector and the wiring harness for loose pins, corrosion, chafing, or heat damage, and repair as needed
Clear the code and test-drive while monitoring live pressure sensor data with a scan tool to see if the signal drops out intermittently
Perform a resistance and continuity test on the sensor/switch 'A' circuit from the sensor connector to the TCM, looking for intermittent opens or shorts while wiggling the harness
Replace the transmission fluid pressure sensor/switch 'A' if circuit tests are inconclusive and the sensor is accessible
If the sensor is internal and requires transmission removal, verify the TCM and wiring first to avoid unnecessary internal repairs
After repairs, clear codes and perform a relearn or adaptation drive cycle as required by the manufacturer, then verify the code does not return

Intermittent faults hide in plain sight

An intermittent code like P0844 often sets only during specific conditions such as cold starts, sharp turns, or vibration over rough roads, so a simple static test may pass even when the fault is real.
A loose ground connection for the transmission or TCM can mimic a sensor circuit fault, so always verify grounds before condemning the sensor.
Some vehicles use a pressure switch rather than a variable pressure sensor for 'A', and a sticking switch can produce the same intermittent code without any drivability symptom.
Aftermarket transmission fluid that is not the specified type can cause pressure variations that trigger this code, especially in cold weather.
The code does not always mean the sensor is bad; a failing transmission pump or valve body can create pressure spikes that the sensor reports as circuit glitches.

Can I keep driving with P0844?

You can usually continue driving short distances if the vehicle shifts normally, but avoid heavy towing or aggressive acceleration until the fault is repaired. If the transmission enters limp mode or shifts harshly, have it diagnosed promptly to prevent further damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.