Fault code P0718 – input/turbine speed sensor “A” circuit intermittent/erratic

Fault code P0718 is called “Input/Turbine Speed Sensor “A” Circuit Intermittent/Erratic” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0718

This Diagnostic Trouble Code (DTC) is a general powertrain code. Error P0718 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

Fault code P0718 – input/turbine speed sensor

Fault code P0718 is displayed when the transmission control module (PCM) detects an intermittent signal in the circuit for the turbine speed sensor, known as “A”. The “A” designation is usually reserved for OBD-II equipped vehicles that use multiple turbine speed sensors.

The turbine speed input sensor is usually an electromagnetic three-wire sensor. Used to monitor the input transmission speed (recognized by the PCM as revolutions per minute).

The sensor is located near the rear of the torque converter (on the transmission input shaft). It is either mounted with a bolt or screwed directly into the transmission crankcase.

There are special grooves on the transmission mainshaft that run close to the end of the sensor. When the grooves pass the transducer, the circuit is interrupted and an electronic pulse is generated. This pulse, is received by the PCM as a waveform pattern, which it recognizes as the turbine speed input.

The turbine speed input is compared to the engine speed, engine load percentage, and transmission output speed. This is done to determine the desired rpm input speed. If the signal in the circuit is faulty or intermittent, code P0718 will be stored and the “Check engine” fault light will illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P0718 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Check engine control lamp on the control panel will light up (the code will be recorded in the ECM memory as a malfunction).
  2. Fluctuating speedometer or odometer readings.
  3. Hard or unstable gear shifting.
  4. Failure of automatic transmission to shift.
  5. Increased fuel consumption.
  6. Floating engine revolutions, as well as attempts to stall.
  7. Stalling of the engine while idling.
  8. Ignition skips in the engine cylinders may occur. Also, the car’s engine may run erratically.

In some cases, when this code is present, the PCM puts the transmission into “emergency operation mode”. In this mode, the transmission begins to operate with limitations. If the transmission begins to shift irregularly when P0718 is reported, the error problem should be corrected immediately.

Factors that can cause this error code

The error code P0718 can mean that one or more of the following problems have occurred:

  • Damaged wiring or connectors.
  • Defective input speed sensor.
  • Faulty output speed sensor.
  • Faulty shift solenoid valve.
  • Contamination of ATF transmission fluid.
  • Accumulation of metal debris on magnetic sensor.
  • Low level of transmission fluid.
  • PCM failure or PCM programming error.

How to fix or reset OBD-2 code P0718

Some suggested steps for troubleshooting and fix the error code P0718:

  1. Connect an OBD-II scanner to the vehicle and read any error codes present.
  2. Clear the codes and test-drive the vehicle to see if there is a problem.
  3. Check the level and condition of the transmission fluid. If the level is low, refill the fluid. When the fluid is contaminated, replace it.
  4. If the error code does not disappear, check the transmission input speed sensor reference voltage and ground signal. Also check sensor circuit continuity and resistance.
  5. Repair or replace any damaged wires or circuits.
  6. If circuits and wires are OK, check all related sensors and solenoid valves.

Diagnose and repair of problems

Check error code P0718 in the Technical Service Bulletins (TSB) for your vehicle. Your problem may have a fix issued by the manufacturer, which may save time and money during diagnosis.

Start your diagnostics by visually inspecting the system wiring and connectors. Damaged wiring as well as connectors should be repaired or replaced. Don’t forget to check the battery and inspect the cables connected to it, also check the alternator power.

Connect the scanner to the diagnostic port, retrieve any stored codes for later use. If input and output sensor codes are present, determine which circuit is faulty.

Make sure there is no excessive metal debris on the magnetic surfaces of the sensors. For best results, remove excessive debris before reinstalling. After removing the sensors, also inspect the grooves and notches on the transmission shaft.

Use a multimeter to test the individual sensors according to the manufacturer’s specifications. Sensors that do not meet the specifications must be replaced.

Before testing resistance and continuity with a multimeter, disconnect the appropriate controllers. Failure to do so may result in controller failure.

Note a faulty PCM or PCM programming error. If all system circuits and sensors are in proper working order and meet manufacturer’s specifications.

On which vehicles does this problem occur most frequently

Fault code P0718 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Ford (Focus)
  • Honda (Accord, Civic, Fit)
  • Isuzu
  • Mazda
  • Mercedes
  • Subaru
  • Volkswagen

Fault code P0718 can sometimes be found with other errors. The most common are the following: P0705, P0715, P0716, P0717.


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