P0718

Input/Turbine Speed Sensor A Circuit Intermittent

P0718 is a generic OBD-II powertrain diagnostic trouble code: Input/Turbine Speed Sensor A Circuit Intermittent. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0718
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P0718 means

P0718 means the control module has seen an intermittent or erratic signal from the transmission's input (turbine) speed sensor, circuit A. That sensor reads the rotational speed of the transmission input shaft or torque converter turbine, normally by counting teeth or a target ring passing a magnetic or Hall-effect pickup. The transmission control module compares input shaft speed against engine speed and output shaft speed to work out torque converter slip, gear ratio and whether a shift completed as commanded.

The module does not just check the signal for being high, low or missing. It also checks it for plausibility over time. If the reading drops out momentarily, jumps to an impossible value, or disagrees with engine and output speed for a short interval and then recovers, the module logs P0718 as an intermittent circuit fault. Because the trigger is transient rather than a hard failure, the code frequently sets while driving, on rough roads or when the harness is hot, and then leaves no obvious symptom by the time the vehicle reaches the workshop.

Input speed is a core input for shift control, so the module reacts defensively. Typical consequences are frozen shift adaptation, harsh or delayed changes, a locked torque converter clutch strategy, or a drop into failsafe where the transmission holds one gear. On some vehicles an erratic input signal also disturbs the speedometer or cruise control. Because the sensor sits in the transmission and shares its harness route, fluid leaks and metal debris in the fluid are recurring contributors.

Common causes

Most-frequently reported root causes when P0718 is logged.

  • 1
    Chafed, broken or corroded wiring in the input speed sensor circuit, often where the harness flexes or passes near hot components.
  • 2
    A loose, backed-out or water-contaminated connector at the sensor or the transmission case.
  • 3
    Metal debris from internal wear clinging to the magnetic tip of the input speed sensor, distorting its output.
  • 4
    A degraded input speed sensor whose signal amplitude falls away when hot.
  • 5
    A transmission fluid leak that wicks along the harness and contaminates the connector.
  • 6
    A damaged, chipped or contaminated reluctor or tooth pattern on the input shaft target.
  • 7
    Electrical interference or a poor shield or ground on the sensor circuit, especially after aftermarket wiring work.
  • 8
    A fault or outdated software in the transmission control module input circuitry.

Symptoms drivers notice

Harsh, delayed or flaring gear changes that come and go rather than happening every time.
The transmission occasionally drops into failsafe and holds a single gear until the engine is restarted.
Check engine light on, sometimes with a transmission warning message.
The speedometer or gear position display may flicker or read incorrectly on some vehicles.
Cruise control cuts out or refuses to engage.
Slightly worse fuel economy because the transmission is not shifting or locking the converter as intended.

How to diagnose P0718

A typical diagnostic flow when this code is present.

  1. 1
    Read all stored codes and freeze-frame data across modules, and note the conditions recorded when the fault set, since intermittent faults are diagnosed from those conditions.
  2. 2
    Check the transmission fluid level and condition, and look for metal debris or a burnt smell that would point to internal wear feeding the sensor problem.
  3. 3
    Inspect the sensor, its connector and the whole harness route for chafing, corrosion, fluid contamination, heat damage and loose pins.
  4. 4
    Monitor input shaft speed alongside engine speed and output shaft speed in live data on a test drive and look for dropouts or implausible spikes.
  5. 5
    Perform a wiggle test on the harness and connector while watching live input speed, ideally at operating temperature, to reproduce the intermittent break.
  6. 6
    If a scope is available, capture the sensor waveform while driving to see whether the signal loses amplitude or picks up noise before it drops out.
  7. 7
    Check for manufacturer service bulletins and control module software updates, then remove and inspect the sensor tip for debris, and only replace the part or repair the wiring that the testing actually implicated.

Related powertrain codes

Frequently asked questions

Can I keep driving with P0718?

Light, careful use is usually possible, but it is not safe to rely on. The transmission can drop into failsafe without warning and limit you to one gear at low speed, which is dangerous in fast traffic. Repeated harsh or flaring shifts also cause real internal wear over time.

Why does the fault disappear before I reach the garage?

Because the code is specifically for an intermittent condition. A wire that only breaks contact under vibration or heat, or debris on the sensor tip that shifts position, reads perfectly fine when the vehicle is cold and stationary. That is why a live-data wiggle test and a road test matter more than a static resistance check.

Will it fail an emissions test?

Yes in most regions, because the code turns on the check engine light. An OBD-based inspection fails a vehicle with an active MIL and a stored code regardless of what the exhaust gas measurements show.

Is this an expensive repair?

Often not. Many cases turn out to be a damaged wire, a corroded connector or debris on the sensor, all of which are inexpensive. The sensor itself is a moderate cost, and it becomes expensive only when the pickup is buried inside the transmission or when the debris that caused it reveals internal wear.

Disabling P0718 in software

RaceTune can permanently disable P0718 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECU families we can disable P0718 on

We hold the DaVinci A2L disable definitions for these families, so the exact P0718 path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch EDC17C66 verified
  • Bosch EDC17CP57 verified

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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