P0718

Code

Generic P — Powertrain

Input/Turbine Shaft Speed Sensor A Circuit Intermittent

Brand: Generic

Type: P — Powertrain

Views: UK: 33 EN: 61 RU: 47

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Causes

Damaged or corroded connector at the ITS sensor
Broken, chafed, pinched or shorted wiring in the ITS circuit
Intermittent internal sensor failure
Poor ground or reference voltage to the sensor
Intermittent ECU/TCM/PCM input or connector problem
Contaminated or mechanically damaged sensor or tone wheel

Symptoms

Check Engine Light (CEL)/Malfunction Indicator Lamp (MIL) illumination
Intermittent transmission shifting problems (harsh, delayed, slipping)
Erratic speedometer or drivetrain-related warning messages (if vehicle uses ITS for speed)
Stalling or difficult to start in some cases (if module uses input speed for control)
Intermittent limp-home mode of transmission

What to check

Retrieve freeze frame and live data with a scan tool; note when the code set and what other codes exist
Monitor ITS sensor live data (and compare to Vehicle Speed Sensor/Output Shaft Speed) for dropouts or mismatching signals
Perform a visual inspection of the harness and sensor connector for corrosion, water intrusion, broken wires, or pin damage
Wiggle test harness/connectors while monitoring live data to try to reproduce the intermittent
Backprobe the sensor connector to measure reference voltage, ground, and signal with a multimeter or oscilloscope
Measure sensor resistance/continuity (if applicable) and check for short to ground or battery

Signal parameters

Hall-effect type: digital square wave, 0–5 V (logic switching) with frequency proportional to shaft speed; 50% approximate duty cycle
Variable-reluctance (VR) type: AC sine/alternating waveform, amplitude increases with shaft speed (typical idle voltage small, increases with rpm)
Signal frequency should increase smoothly with shaft speed without dropouts or erratic pulses
Reference supply: many Hall sensors require a stable 5 V reference and a good ground; verify reference is present with key ON
Noisy or missing waveform, intermittent loss of signal, or erratic amplitude are symptomatic of the fault

Diagnostic algorithm

Connect a scan tool, read codes and freeze frame, then clear codes and attempt to re-create the fault by driving or operating the transmission under various conditions.
Monitor ITS sensor live data and compare to VSS/OSS or engine RPM; note any intermittent signal loss or disagreement between sensors.
Visually inspect the ITS sensor connector and harness from the sensor back to the module for damage, corrosion, or water intrusion. Repair any obvious wiring damage.
With key ON (engine off) backprobe the sensor connector: verify 5 V reference (if Hall type), good ground, and signal present. If reference or ground intermittent, trace to their source and repair.
With an oscilloscope (preferred) or DVOM (less ideal), observe the ITS signal while cranking and during road test. Look for clean square wave (Hall) or clean AC waveform (VR) that changes smoothly with speed. Note any dropouts or noise spikes.
Wiggle test the harness and connectors while monitoring the live signal/oscilloscope to try to reproduce intermittent behaviour. Repair or replace wiring/connectors where intermittent is found.
Measure sensor coil resistance (if VR type) and check for short to ground or battery. Compare to manufacturer specification if available. Replace sensor if out of spec or intermittent.
Inspect reluctor/tone wheel and sensor mounting for damage, missing teeth, excessive air gap, or debris. Correct mechanical issues (clean, adjust gap, or replace tone wheel/sensor).
If sensor and wiring check good, inspect PCM/TCM connector pins and grounds; repair any looseness or corrosion. If intermittent input at module persists, consider module input fault — consult manufacturer service information before replacement.
After repairs, clear codes and perform functional test/road test to confirm absence of intermittent P0718 and verify proper transmission operation.