Transmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance
The automatic gearbox has its own control unit (TCM), which decides when to shift using speed, temperature, pressure and selector position sensors. The gearbox oil pressure sensor (or pressure switch) tells the control unit the hydraulic pressure used to engage clutches and gears. This code means its signal doesn't make sense.
What the car has detected
The pressure reported by sensor or switch A doesn't match what is expected for the gearbox's state.
Wrong pressure can make clutches slip and wear, and the control unit may go into limp mode. Get it checked soon and don't push the gearbox.
Symptoms
- Engine or gearbox warning light on
- Harsh or jerky shifts
- The gearbox slips or is slow to engage
- Limp mode
Possible causes
- Low gearbox oil pressure (low level or leaks)
- Faulty pressure sensor wiring or connector
- Failed mechatronic unit (the gearbox's control unit and valves)
- Faulty valve body or pressure sensor
Checks for the garage
- Check the gearbox oil level and condition per the manufacturer's procedure
- Measure the gearbox oil pressure
- Check the sensor wiring and connector
- Check the mechatronic unit or valve body if the above is fine
Next step
Have the gearbox oil level and pressure checked before replacing parts, then the sensor and the mechatronic unit or valve body.
Go to a garage: measuring pressure and checking the mechatronic unit needs manufacturer equipment. On dual-clutch gearboxes it is a known fault in some mechatronic units.