P0718: Input/Turbine Shaft Speed Sensor A Circuit Intermittent
What to do
If the transmission drops into a single gear briefly and then recovers, that is this fault rather than your imagination. Note whether it happens when hot, over bumps or under load — all three point somewhere different.
What this code means
The input shaft speed signal cuts out briefly and returns. Because so much of the module's logic depends on this measurement, even a momentary loss can trigger a protective shift into a fixed gear — so the driver's experience is a transmission that suddenly goes wrong for a few seconds and then behaves normally again, often several times a journey.
That pattern is worth taking seriously rather than clearing, both because it usually progresses to a permanent fault and because a momentary limp-mode engagement at speed is unpleasant enough to be a safety consideration of its own.
Likely causes
Start here
- Damaged transmission wiring harness · moderate
- Corroded transmission connector · moderate
- Faulty turbine speed sensor · specialist
Less common
- Metal debris on the sensor tip · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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