Code P0718 indicates that the Powertrain Control Module (PCM) has detected an intermittent or erratic signal from the input/turbine shaft speed sensor. This sensor monitors the rotational speed of the transmission's input shaft, which the PCM uses to calculate shift timing and torque converter operation. An intermittent signal means the PCM is temporarily losing the speed reading, often due to a electrical connection that cuts out when the vehicle hits bumps or reaches certain temperatures.
Corroded, loose, or chafed wiring and connectors are the most common causes of an intermittent signal, disrupting the circuit when the vehicle moves or vibrates.
The sensor itself may have an internal intermittent failure, causing it to drop the signal sporadically as it heats up or experiences vibration.
Insufficient or dirty fluid can cause the sensor to lose its reading, or introduce air bubbles that intermittently disrupt the signal.
A broken reluctor ring or damaged input shaft can cause the sensor to read intermittently if the physical gap between the sensor and the tone ring fluctuates.
A rare cause where the control module itself has an internal fault affecting how it processes or receives the sensor signal.
It is not recommended. The transmission may shift erratically or enter limp mode, which can cause further drivetrain damage and make the vehicle unsafe to drive.
Not usually. While an internal mechanical issue can cause this, the most common causes are external electrical issues like a faulty sensor or damaged wiring.
Almost never. Replacing the PCM is a common misdiagnosis for this code. An intermittent signal is far more likely to be caused by a wiring issue, a bad connector, or a failing sensor itself. The control module is rarely at fault.
The transmission control system relies on input shaft speed to calculate shift points and torque converter lockup. An intermittent signal causes the system to lose track of shaft speed, leading to harsh or unpredictable shifts.