P0718 — Intermittent problem with transmission input speed sensor circuit

The code indicates a problem with the input (turbine) speed sensor signal in the transmission. This sensor helps the transmission control module monitor how fast the input shaft is spinning. An intermittent circuit issue means the sensor signal is cutting in and out, which can cause shifting problems or transmission performance issues.

Common causes

The cause is almost always one of a few things. Here they are — P0718 rarely comes from anything outside this list:

• Damaged or corroded sensor wiring or connectors
• Faulty input/turbine speed sensor
• Poor electrical connection at the sensor or ECU
• Intermittent internal sensor failure
• Transmission control module issues (less common)

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Inspect and clean sensor connectors and wiring
2. Repair or replace damaged wiring or connectors
3. Test sensor output and replace sensor if faulty
4. Check transmission control module connections
5. Replace transmission control module if necessary

That is what holds for P0718 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.