P0715 is a generic and somewhat rare OBDII trouble code. Although this code can appear on any vehicle, it is most common to see it on cars and trucks made by Mercedes, Ford, and Nissan.
Simple explanation: P0715 indicates that there is a communication error with the sensor that measures the transmission input speed
Common causes A faulty transmission speed sensorTransmission solenoid, wiring problems, and even a lack of transmission fluid can cause P0715.
P0715 Definition: Turbine “A” speed sensor/input circuit malfunction
Here is the definition of P0715 broken down into its two parts:
Turbine Speed Input/Sensor
The input/turbine speed sensor measures the speed of the transmission input shaft. It does this by measuring the speed of a reluctant wheel using electromagnets.
The reluctant wheel has some notches. By rotating the input shaft, the input/turbine speed sensor can tell each time it passes one of these notches.
It transmits this data to the ECU or TCM, which uses it to determine the speed of the input shaft. The PCM then compares this data to the engine RPM, output shaft speed sensor, and vehicle speed.
If the input shaft/turbine speed reading does not match the variables listed above, a trouble code will be issued and the check engine light will illuminate.
The intake/turbine speed sensor is usually bolted to the transmission case, so you won’t have to take the transmission apart to check it.
The input/turbine speed sensor is sending a signal to the PCM that it is out of range. If it is not known how fast the input shaft is rotating, the transmission will not shift correctly (or at all), and P0715 will be issued.
The most common symptoms of P0715 are
- Abrupt changes
- Limping mode
- Stalls when slowing down (rare)
- speedometer not working
P0715 Causes + Diagnosis
Here’s a solid way to diagnose P0715.
1. Check the transmission fluid
Make sure the transmission fluid level is full. A low transmission fluid level will cause the input shaft speed to increase relative to the engine speed (slip).
Dirty transmission fluid can also cause P0715. Burnt or dirty transmission fluid cannot do its job efficiently, which can cause the input speed to change relative to the output speed.
In this situation, the entry speed will be too high compared to the exit speed and the vehicle speed.
2. Inspect the input speed sensor wiring
The wiring to the input speed sensor may be damaged. Make sure there are no frayed or damaged cables. If there is, replace it.
Inspect where the harness connects to the input speed sensor. Check that it is not visibly damaged. Do the pins appear free of corrosion? They may need cleaning to make good contact.
3. Input shaft sensor voltage test
Next, you will need to test the voltage and check the ground connection at the turbine input/speed sensor. From here there can only be two situations:
- The tension is fine– At this point, replacing the sensor will probably clear P0715.
- Voltage problem– The wiring may look fine, but you will have to find where the voltage drops and repair the harness. A good mechanic has diagnostic equipment that can make this task easier for you.
4. Transmission problems
Repairing P0715 usually involves the turbine/input speed sensor and its wiring, but internal transmission problems can cause it.
A bad valve body or shift solenoid can cause P0715.
P0715 is usually caused by a faulty turbine input or speed sensor.