What does it mean?
P1718 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: TFT Sensor No Activity Or TFT Sensor Circuit High Input .
Symptoms
- MIL on, often with a transmission warning
- Fluid temperature in live data stuck at an extreme value, usually the coldest reading
- Harsh or delayed shifts, particularly once the transmission is hot
- Torque converter lock-up disabled, leaving higher engine speed at cruise
- Limp mode with a fixed gear
- Increased fuel consumption and the risk of the transmission overheating unnoticed
Likely causes
- Open circuit in the transmission fluid temperature sensor or its wiring
- Transmission case connector disconnected or corroded
- Sensor signal frozen at one value and never changing as the transmission warms up
- Internal transmission harness damaged by heat or fluid
- Short to a reference or supply voltage on the signal circuit
- Failed sensor element inside the sensor body
- Module input circuit or sensor ground return fault
How to fix it
- Watch the fluid temperature value while the transmission warms up; a value that never moves confirms no sensor activity
- Compare it with the coolant temperature after an overnight soak, since they should read close together
- Measure the sensor resistance at the case connector against the temperature and resistance table
- Test the signal wire for continuity to the module and for a short to a voltage source
- Inspect the case connector for corrosion, fluid intrusion and pushed-out terminals
- Check the sensor ground return circuit for continuity and voltage drop
- Replace the sensor or the internal harness assembly if the element is electrically open