P0879 Transmission fluid pressure sensor / switch D circuit malfunction
Content
P0879 Transmission fluid pressure sensor / switch D circuit malfunction
OBD-II DTC Datasheet
Transmission Fluid Pressure Sensor / Switch Circuit Malfunction D
What does this mean?
This Generic Transmission / Engine DTC usually applies to all OBD-II equipped engines, but is more common in some Dodge / Chrysler / Jeep, General Motors and Toyota vehicles.
The transmission fluid pressure sensor / switch (TFPS) is usually found attached to the side of the valve body inside the transmission, although it can sometimes be found screwed into the side of the transmission case / housing itself.
TFPS converts the mechanical transmission pressure into an electrical signal for the powertrain control module (PCM) or transmission control module (TCM). Typically, the PCM / TCM will then inform the other controllers using the vehicle's data bus.
The PCM / TCM receives this voltage signal to determine the operating pressure of the transmission or when a gear change is occurring. This code is set if this input does not match the normal operating voltage stored in the PCM / TCM memory. It can also be due to internal mechanical problems within the transmission.
P0879 is usually an electrical circuit problem (TFPS sensor circuit), although as previously stated, this code can also be set due to mechanical problems (internal leaks, cracks or missing test balls in the valve body, low system working pressure / pressure in the line, the valve is stuck in the valve body). This should not be overlooked during the troubleshooting phase, especially when dealing with an intermittent problem.
Troubleshooting steps may vary depending on manufacturer, TFPS sensor type, and wire colors.
Related Transmission Fluid Pressure Sensor D Codes:
- P0875 Transmission fluid pressure sensor / switch "D"
- P0876 Transmission Fluid Pressure Sensor / Switch "D" Circuit Performance Range
- P0877 Transmission fluid pressure sensor/switch "D" - circuit low
- P0878 A high rate sensor / switch transmission fluid pressure "D"
Code severity and symptoms
The severity depends on which circuit the fault occurred on. Since it could be an electrical fault or a mechanical fault, the PCM / TCM can compensate for it to some extent. A malfunction could mean that the PCM / TCM is modifying the transmission shift when electronically controlled.
Symptoms of a P0879 engine code may include:
- Fault indicator light is on
- Change the quality of the shift
- The car starts to move in 2nd or 3rd gear (limping in mode).
reasons
Usually the reason for installing this code is:
- Intermittent open in the signal circuit to the TFPS sensor
- Intermittent short to voltage in the signal circuit to the TFPS sensor
- Intermittent short to ground in signal circuit to TFPS sensor
- Faulty TFPS sensor - probably
- Problem with internal manual transmission - possible
- Faulty PCM - unlikely (requires programming after replacement)
Diagnostic and repair procedures
A good starting point is always to check the Technical Service Bulletins (TSB) for your particular vehicle. Your problem may be a known issue with a known manufacturer-released fix and could save you time and money while troubleshooting.
A good example of this would be if there are any known power related codes set with P0879, or if more than one set of pressure sensor / switch codes are set. If so, start diagnostics first with a power-related DTC or diagnose multiple codes first, as this may be the cause of the P0879 code.
Then locate the Transmission Fluid Pressure (TFPS) sensor / switch on your specific vehicle. The TFPS is usually found attached to the side of the valve body inside the transmission, although it can sometimes be found screwed into the side of the transmission case / housing itself. Once found, visually inspect the connector and wiring. Look for scratches, scuffs, exposed wires, burn marks, or molten plastic. Disconnect the connector and carefully inspect the terminals (metal parts) inside the connector. See if they look burnt or have a green tinge indicating corrosion, especially if they are attached outside the gearbox housing. If you need to clean the terminals, use an electrical contact cleaner and a plastic bristle brush. Allow to dry and apply electrical grease where the terminals touch.
If you have a scan tool, clear the DTCs from memory and see if P0879 returns. If this is not the case, then there is most likely a connection problem.
This is the most common area of concern in this code, as external transmission connections have the most corrosion problems.
If the P0879 code does return, we will need to test the TFPS sensor and associated circuits. With the key off, disconnect the electrical connector at the TFPS sensor. Connect the black lead from the digital voltmeter (DVOM) to the ground or low reference terminal on the TFPS sensor harness connector. Connect the red lead from the DVM to the signal terminal on the TFPS sensor harness connector. Turn on the engine, turn it off. Check manufacturer specifications; the voltmeter should read 12 volts or 5 volts. Rock the connections to see if they have changed. If the voltage is not correct, repair the power or ground wire or replace the PCM / TCM.
If the previous test was successful, connect one lead of the ohmmeter to the signal terminal on the TFPS sensor and the other lead to ground or the low reference terminal on the sensor. Check the manufacturer's specifications for the resistance of the sensor to accurately test the resistance to pressure when no pressure is applied to it. Wiggle the connector on the transmission fluid pressure sensor / switch while checking the resistance. If the ohmmeter reading does not pass, replace the TFPS.
If all previous tests have passed and you continue to receive P0879, it will most likely indicate a failed TFPS sensor, although a failed PCM / TCM and internal communication failures could not be ruled out until the TFPS sensor was replaced. If you are unsure, seek help from a qualified automotive diagnostician. To install correctly, the PCM / TCM must be programmed or calibrated for the vehicle.
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