Transmission Fluid Pressure Sensor/Switch A Circuit High
What it means
P0843 means the transmission control module reads an abnormally high voltage from the "A" fluid-pressure sensor/switch — the sensor that reports hydraulic line pressure inside the transmission. The engine still runs, but because the module can't trust the pressure reading it may command harsh shifts, allow slipping, or drop into a protective limp mode. Left unfixed, poor pressure control can accelerate transmission wear.
Can I keep driving? The engine starts and runs, but the transmission may shift harshly, slip, or enter a limp mode; drive gently and get it looked at soon to avoid transmission wear.
Common symptoms
What you'll notice
- Check-engine light on
- Harsh or delayed shifting
- Transmission slips or won't engage properly
- Transmission drops into a fail-safe (limp) mode
Common causes
Most likely first
- Faulty transmission fluid pressure sensor/switch ALikely
- Open or short to power in the sensor wiring (reads high)Common
- Loose or corroded connector at the sensorCommon
- Failed transmission control module (TCM)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check transmission fluid level and condition first.
- Inspect the pressure-sensor connector and wiring for damage, corrosion, or shorts to power.
- Compare the sensor's signal voltage against service data; replace the pressure sensor/switch if out of range.
- If wiring and sensor are good, suspect the TCM. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0843?+
Can I just clear P0843?+
Related codes
Often seen with P0843
Read & clear P0843 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.