Transmission Fluid Pressure Sensor/Switch "D" Circuit Range/Performance

Possible causes

• CommonGenuinely low line pressure - low fluid, blocked filter, worn pump
• CommonFailing or drifting pressure sensor
• CommonSticking valve in the valve body
• CommonWorn clutch pack leaking pressure past its seals
• PossibleFailed pressure control solenoid
• PossibleDebris partially blocking the passage to the sensor

What you might notice

• Slipping under load
• Harsh, delayed or flaring shifts
• Limp mode
• Burnt smell from the fluid
• Check engine light on

What to check, in order

1. Check the fluid level and condition first, and look for clutch material in it.
2. Establish whether the transmission is actually slipping. If it is, the sensor is probably telling the truth and the fault is hydraulic or mechanical.
3. A line pressure test with a gauge is the way to separate a lying sensor from real low pressure. It is worth paying for before buying parts.
4. Check the transmission filter if it has never been changed - a blocked filter starves the pump and produces low pressure everywhere.
5. Read all codes. Ratio or solenoid codes alongside this one indicate a hydraulic problem rather than a sensor one.
6. Do not keep driving a transmission that is slipping. Clutches destroy themselves quickly once they start.