P0718 Code: Input/Turbine Speed Sensor A Circuit Intermittent

What the P0718 code means

The input speed sensor (also called the turbine speed sensor) measures how fast the input shaft of the transmission turns, after the torque converter. With it, the computer works out torque converter slip and the gear ratio in each gear.

The sensor generates pulses whose frequency depends on the speed or the quantity being measured. Intermittent dropouts are almost always caused by a poor contact or a damaged wire. That is what sets the P0718 code.

Without this signal, the computer cannot verify the gear ratios and puts the transmission in limp mode, usually in a fixed gear. Metal shavings that stick to the magnet of the sensor are a frequent cause of wrong readings. See the sensor guide to learn how to test it.

Intermittent faults are found by reproducing them: with the engine running and the scan tool in graph mode, move the wiring harness section by section, tap the connector gently and, if needed, warm the area with a hair dryer or spray the connector with water. The point where the reading jumps is the point of the fault.

P0718 code symptoms

• Check engine light on.
• Transmission in limp mode.
• The transmission does not shift or stays in a fixed gear.
• Harsh shifts.

Likely causes of the P0718 code

1. Poor contact in the connector, with loose or backed-out pins.
2. Wire broken inside the insulation, which opens the circuit with vibration.
3. Harness rubbing on moving or hot parts.
4. Sensor with an intermittent fault, often related to temperature.

How to diagnose the P0718 code step by step

1. Read the sensor value on the scan tool and compare it with what is expected.
2. Inspect the connector for corrosion, water and loose pins.
3. Check power and ground with the key on: a correct reference and less than 0.1 volt drop on the ground.
4. Measure the signal with the connector plugged in and see whether it changes with the condition.
5. Do a wiggle test of the wiring with the scan tool in graph mode.
6. Check the continuity of each wire back to the computer (under 1 ohm).
7. Remove the sensor and clean its tip. Metal shavings distort the signal.

How to fix the P0718 code

• Repair the connector or the wiring.
• Replace the sensor if the tests confirm it is bad.
• Correct the real condition if there is one.
• Clear the P0718 code and verify with a road test.

Technical reference data

• Inductive sensor (2 wires) or Hall effect sensor (3 wires).
• Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

The source reports this code as frequent on three transmission families.

P0718 on Aisin

Frequent on Aisin transmissions. Pull the sensor and check its tip for metal shavings.

P0718 on Jatco

Frequent on Jatco transmissions. Pull the sensor and check its tip for metal shavings.

P0718 on GM 4L60/4L65

Frequent on the GM 4L60 and 4L65 transmissions. Pull the sensor and check its tip for metal shavings.

Frequently asked questions about P0718