The ECU needs to collect lots of data from different areas of the vehicle, so it can determine things like engine timing and shift patterns. Naturally, the transmission fluid pressure sensor is a very important data source. So if the ECU detects an intermittent signal coming from this sensor, a P0879 DTC will be stored.
How Serious is the Code?
If the ECU detects that there is either a problem with the TFPS sensor, or the amount of hydraulic pressure inside the transmission, a number of transmission problems and drivability concerns will ensue. So a P0879 diagnostic trouble code is very serious.
Symptoms of a P0879 include:
- Overheated transmission
- Transmission won’t go into gear
- Low on the transmission fluid
- The transmission filter and fluid need to be changed
- Transmission fluid leak
- Overheating transmission
- Overheating engine
- Corroded or broken connectors
- Damaged or broken wires
- Transmission pump is malfunctioning
- Transmission fluid pressure sensor is malfunctioning
- Transmission fluid temperature sensor is malfunctioning
- TCM is malfunctioning
- Internal mechanical failure
How to Diagnose the Code?
The process of diagnosing a P0879 OBDII trouble code should start with a search of the manufacturer’s technical service bulletin database. If no fixes for these transmission problems are found there, then the wiring and connectors going to the transmission fluid pressure sensor should be checked for signs of damage and corrosion. The sensor itself will also need to be tested to see if it works the way the manufacturer intended. If no issues have been found up to this point, then suspect a mechanical issue inside the transmission like a failing transmission pump or valve body.
What Repairs Will Fix P0879?
- Change the transmission fluid and filter
- Repair transmission fluid leaks
- Repair or replace damaged wiring and sensors on the transmission wiring harness
- Replace the transmission pump
- Replace transmission fluid pressure sensor
- Replace transmission fluid temperature sensor
- Replace or repair valve body
- Replace or repair transmission