The P0718 code in your 2020 Jeep Grand Cherokee indicates that the input/turbine speed sensor is providing an intermittent signal. The sensor communicates sometimes but drops out or becomes erratic intermittently. This creates unpredictable transmission behavior as the TCM loses track of input shaft speed.
Intermittent Signal Behavior
An intermittent input speed signal might cut out momentarily during driving, show sudden jumps or drops, or work fine for periods then fail. The TCM expects a smooth, consistent signal that correlates with driving conditions. Erratic behavior indicates an unstable electrical connection or degraded sensor.
Common Causes in Grand Cherokee
Loose or corroded connector terminals are the most common cause—connections that work sometimes but not consistently. Damaged wiring that makes and breaks contact with vehicle movement creates intermittent behavior. A sensor that's failing progressively may work when cold but fail when hot, or vice versa. Debris that occasionally blocks the sensor gap can cause dropouts.
How This Affects Driving
Transmission operation becomes unpredictable. You may experience momentary harshness during shifts, brief loss of power transfer, or erratic torque converter clutch operation. The transmission might briefly enter and exit failsafe mode. These symptoms often come and go, making the problem frustrating to reproduce for diagnosis.
Diagnostic Approach
Using Chrysler wiTECH, monitor input speed data over an extended drive. Watch for dropouts, sudden changes, or signal instability. Perform wiggle tests on the sensor connector while monitoring—if the signal changes, you've found a loose connection. Drive under various conditions (hot, cold, rough roads) to trigger the intermittent behavior. Check all terminals for proper tension and corrosion.