Why is P0718 harder to diagnose than the other input-speed codes?

Because it's intermittent. P0717 means the signal is permanently gone and P0716 means it's steadily wrong — both are present when you test. P0718 comes and goes, often only over a bump, at a certain temperature, or under vibration, so the fault may be completely absent in the shop and a static test shows nothing. You catch it with freeze-frame data, a recorded drive that reproduces the dropout, and a wiggle-test of the connector while watching the live input-speed reading.

What usually causes an intermittent input speed sensor fault?

Most often a connection problem — a loose or corroded connector, or a wire that's chafed and only opens when it flexes or heats up. Electrical noise and moisture bridging connector pins also produce intermittent dropouts. A sensor starting to fail can throw the occasional glitch before it dies, and a tone ring with one damaged tooth can produce a fault that comes and goes. Inspect connectors and wiring first, since they're cheaper and the most common cause.

Can I keep driving with P0718?

Generally yes, between events the car drives normally. The concern is that each dropout can cause a harsh shift or a momentary limp condition, which adds stress to the transmission over time. It's not an emergency, but intermittent faults tend to worsen — today's occasional glitch becomes a steady failure — so it's worth chasing down before it leaves you stuck in limp mode. Drive gently and get it diagnosed while the fault is still reproducible.

My sensor tested fine — why is the code still there?

That's the classic frustration with intermittent codes. A resistance or signal check that passes only proves the sensor was fine at that instant, not that it's healthy under all conditions. The dropout might only appear when a wire flexes over a bump or a connector warms up. Don't clear the code and call it fixed on a passing static test — reproduce the fault with a live-data drive and a wiggle-test, and trust freeze-frame data over a one-time bench reading.

OBD-II trouble code

P0718: Input / Turbine Speed Sensor Circuit Intermittent

The input (turbine) speed sensor signal is cutting in and out. The defining word here is 'intermittent' — the sensor works most of the time, then briefly drops out or glitches before recovering. That on-again-off-again behavior makes this the trickiest of the input-speed-sensor codes, because the fault is often gone by the time you go looking for it.

Quick facts

System: Powertrain
Category: Transmission / Speed Sensor
Severity: High severity
Drivable: Usually safe to drive short-term
Repair cost range: $120 – $500
DIY difficulty: Intermediate DIY

What does P0718 mean?

P0718 belongs to the input/turbine speed sensor family, but where P0717 means the signal is permanently absent and P0716 means it's present but implausible, P0718 means the signal is intermittently lost — it disappears or glitches briefly, then comes back. The input speed sensor tells the PCM/TCM how fast the transmission input shaft is turning, which the controller uses for gear-ratio calculation, shift timing, and torque-converter lockup. When that signal momentarily drops out, the TCM sees a sudden, impossible change in input speed and flags it, often commanding a brief harsh shift or a momentary limp condition as it reacts.

The intermittent nature is the whole story, and it steers the diagnosis toward connection problems rather than a dead part. A loose or corroded connector that makes and breaks contact, a wire that's chafed or cracked and only opens when it flexes or heats up, and intermittent electrical noise are the classic offenders — the same pattern you see in any intermittent circuit code. A sensor beginning to fail can throw the occasional dropout before it dies completely, and a marginal air gap or a tone ring with a single damaged tooth can produce a glitch that comes and goes with temperature or vibration. Low or aerated transmission fluid can contribute on designs sensitive to it. Because the symptom isn't always present, a static bench test frequently shows nothing.

For the driver, P0718 shows up as occasional harsh or unexpected shifts, a brief flare or lockup hiccup, and a check engine light that may come and go. The car is generally driveable between events. Catching it requires chasing the fault while it's happening: freeze-frame data, a recorded live-data drive that reproduces the dropout, and a wiggle-test of the connector and harness while watching the input-speed reading are the highest-yield tools — far more useful than a one-time resistance check that passes because the fault wasn't present at that moment.

Common causes

Loose or corroded speed-sensor connector making intermittent contact
Chafed or cracked wire that opens only when it flexes or heats up
Intermittent electrical noise on the sensor circuit
Sensor beginning to fail and dropping out occasionally
Marginal air gap or a single damaged tooth on the reluctor / tone ring
Moisture intermittently bridging connector pins
Low or aerated transmission fluid on sensitive designs

Symptoms

Check engine light that may come and go, with P0718 stored
Occasional harsh or unexpected gear changes
Brief flares, slips, or torque-converter lockup hiccups
Transmission momentarily entering and leaving limp mode
Symptoms tied to bumps, temperature, or vibration
Fault often absent when the vehicle is stationary in the shop

Diagnostic steps

1.Pull freeze-frame data first — it captures the conditions present when the intermittent dropout set, the best clue for this code.
2.Read input/turbine speed live data on a drive that reproduces the symptom and watch for momentary drops to zero or sudden jumps.
3.Wiggle-test the sensor connector and harness while watching live data — a glitch during the test localizes a bad connection.
4.Inspect the connector for corrosion, backed-out pins, and moisture intrusion.
5.Check the sensor air gap and the tone ring for a single damaged tooth that would glitch intermittently.
6.Resistance-check the sensor and wiring, looking for a reading that drifts or only goes out of spec when flexed or warm.

Repair cost

$120 – $500

Because P0718 is usually an intermittent connection, wiring and connector repairs are a common and relatively cheap fix at $100-$300 — sometimes just cleaning or re-pinning a connector. A speed sensor replacement runs $150-$400 if the sensor is dropping out. Budget some diagnostic labor, since the hard part of an intermittent code is catching the fault while it's actually happening.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.