P0725 is a common OBD2 code. Indicates a problem with the engine speed sensor input circuit (which measures the engine speed at the input shaft and helps the PCM determine when and how hard to shift the transmission).
Although it is a generic code (it has the same meaning for any vehicle manufactured after 1996), it is more common in vehicles manufactured by Nissan.
P0725 Meaning: Engine Speed Input (Sensor) – Circuit Malfunction
Engine speed input sensor
The engine speed input sensor is responsible for transmitting data to the PCM about the engine speed. Depending on the vehicle in question, May be referred to as transmission input speed sensor, input speed sensor, or engine speed input sensor.
On most transmissions, it threads into the case near the front of the input shaft. A reluctant wheel rotates with the input shaft, and the engine’s input speed sensor uses an electromagnetic field to measure the speed at which it rotates.
The engine speed input circuit sends the data it receives from the input speed sensor to the PCM in the form of a voltage value. It will compare this value to the engine RPM, output speed sensor, and throttle position.
When the voltage value is not theoretically correct when compared with the other sensors, P0725 is stored in the PCM memory.
Although P0725 is not usually a risk of complete breakdown, there will usually be very noticeable symptoms. Here are the most common ones:
- check engine light
- The speedometer and tachometer not working properly (or not working at all)
- Transmission does not shift correctly
- Not all gears are available, and changes are abrupt (limp mode)
P0725 Causes + Diagnosis
These are the most common causes of P0725:
Dirty or low transmission fluid
Since P0725 is a transmission-related fault code. The first thing you should do is check the transmission fluid. If it is brown, black or gray there could be a transmission problem.
If there is a metal flake in the transmission, it can cause the input speed sensor to stop picking up the reluctant wheel.
Speed input sensor wiring problem
After confirming that the transmission fluid is in good condition and has been filled correctly, the next easiest thing to check is the wiring harness leading from the input speed sensor.
Check the wiring harness for cracks or damage. If it appears damaged, replacing it may eliminate P0725.
Inspect the pins where they connect to the speed input sensor. If the pins are damaged or corroded, you will need to clean/replace them or repair the harness.
Bad input speed sensor
A bad input speed sensor is the most common cause of P0725. Before replacing it, inspect the magnetic tip for metal chips.
Here are other causes of P0725:
- Transmission failure: If the transmission slips, it can create metal debris that affects the input speed sensor.
- Defective PCM: This occurs rarely, but is known to cause P0725.
- Defective shift solenoid(s): You will likely see metal debris on the dipstick if this is the case.
Although a bad input speed sensor is perhaps the most common cause of P0725, it is one of many potential causes. Good luck repairing your vehicle.