Input/Turbine Speed Sensor Circuit No Signal
Your transmission's speed sensor isn't sending a signal to the engine computer, like a speedometer that's stopped working. Without this information, the transmission can't shift gears properly or adapt to driving conditions.
The ECM monitors voltage signals from the turbine/input speed sensor to track transmission fluid flow and gear engagement. It expects a frequency signal proportional to input shaft speed; absence of this signal for a calibrated duration triggers the fault. The sensor typically generates AC voltage or digital pulses as the shaft rotates.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Turbine Speed Signal Frequency | 10-10,000 Hz depending on engine load and gear | No signal or signal below minimum threshold for >2 seconds |
| Sensor Voltage Output | 0.2–4.8V (varies by sensor type) | Constant 0V or 5V with no variation |
Code P0718 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0718 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.