What it means
The transmission fluid pressure sensor/switch A reports a circuit intermittent fault. Hydraulic pressure feedback for shift control is unreliable on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Transmission pressure sensor or switch A provides a signal used by the control module to monitor hydraulic pressure during shifts. P0844 sets when the A circuit signal drops out or changes unpredictably at times, making pressure feedback unreliable and potentially triggering restricted shifting.
Common causes
Most likely first.
- Connector not seated
- Harness chafing intermittently
- Connector with intermittent contact under vibration
Symptoms
- Transmission warning light may be on
- Shifting may be abnormal
How to diagnose it
- Record freeze-frame data and review sensor A live data and code status to identify whether the fault coincides with a shift, temperature change, or vibration.
- Inspect sensor A’s connector for a loose fit, damaged latch, corrosion, fluid intrusion, or terminals that can move in the housing.
- Carefully inspect the A circuit harness along its route for chafing, stretching, heat damage, or intermittent contact points.
- With the wiring diagram, monitor the A circuit for dropouts while gently moving the harness and connector, following the manufacturer’s test procedure.
- If the wiring remains stable, test sensor A’s output under the specified conditions and compare it with the manufacturer’s specification.
Common fixes
- Fully seat and secure a loose sensor A connector.
- Repair chafed or strained wiring and secure the harness to prevent recurring movement.
- Repair or replace connector terminals that lose contact under vibration.
- Replace sensor A if it intermittently drops out while its connector and wiring remain sound.
Can I keep driving?
Because this fault can cause the transmission to enter limp mode or shift unpredictably, avoid long trips, towing, and high-speed driving. If the transmission slips, loses drive, or becomes stuck in a gear, stop in a safe place and arrange appropriate assistance.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.