P0718 — Input/Turbine Speed Sensor « A » Circuit Intermittent

**Introduction**

The diagnostic trouble code (DTC) P0718 indicates an issue with the Input/Turbine Speed Sensor « A » circuit. This sensor plays an essential role in measuring the rotational speed of the turbine within the vehicle’s transmission. When the circuit becomes intermittent or signals irregularly, the vehicle’s powertrain control module (PCM) detects this abnormality and triggers the P0718 warning. It’s important to understand that labeling and terminology can vary slightly between different Original Equipment Manufacturers (OEMs).

**Fast Facts**

  • System affected: Transmission control system
  • Severity: Moderate
  • Main symptoms: Transmission shifting issues, warning lights, reduced driveability
  • Driveability: Limited

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Manufacturer variations for trouble code P0718

The P0718 code may have different labels depending on the vehicle manufacturer. Many OEMs use their own coding or terminology for similar sensor issues. Common label variations include:

  • Ford: P1740 — Transmission Input/Turbine Speed Sensor « A » Circuit Intermittent
  • Volkswagen / Audi: P0718 (sometimes labeled as « Input Signal Fault »)
  • BMW / Mini: P0718 (may be integrated into broader transmission control fault codes)
  • Hyundai / Kia: P0718 (diagnostic label may include « Input Speed Sensor Circuit Malfunction »)
  • Mercedes-Benz: No specific label, but similar circuit faults are classified under transmission sensor issues

*Note: Always consult the specific manufacturer’s repair manual or diagnostic information for precise labelling.*

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What does trouble code P0718 mean?

The P0718 code signifies that the vehicle’s ECU (Engine Control Unit) has detected an abnormal or intermittent signal from the Input/Turbine Speed Sensor « A ». This sensor measures how fast the turbine (part of the torque converter) spins, which provides critical data for the transmission’s control system to operate smoothly.

The ECU continuously monitors this input for consistency. If the signal becomes unstable, drops out, or shows irregular fluctuations, it considers the circuit « intermittent » and flags this fault.

Typically, the code triggers due to **electrical issues** (such as wiring problems), **sensor malfunctions**, or **transmission control system abnormalities**. This could happen under certain driving conditions, such as during shifts, or when components are failing gradually.

*In essence, the sensor acts as the vehicle’s speedometer for transmission components, and this fault indicates that the data it provides cannot be trusted reliably.*

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Severity and risks of trouble code P0718

The P0718 is classified as a moderate severity fault. It does not usually cause immediate vehicle breakdown but can lead to significant transmission operational issues if left unrepaired.

**Potential risks include:**

– Improper shifting or slipping transmission
– Harsh gear changes
– Increased wear on transmission components
– Potential for complete transmission failure in extreme cases
– Reduced driving comfort and efficiency

**Can the vehicle be driven?**
Answer: Yes, with caution, but it is advisable to address the fault promptly. Prolonged driving with this issue can worsen transmission damage or cause further mechanical problems.

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Symptoms of trouble code P0718

When the P0718 is active, drivers may notice subtle to significant symptoms, depending on the severity and duration of the fault. Common signs include:

  • Transmission warning light or check engine light comes on
  • Erratic shifting or delayed gear engagement
  • Transmission slipping or abrupt gear changes
  • Reduction in driving smoothness or comfort
  • Unusual noise from the transmission
  • Limited transmission response during acceleration

Many of these symptoms often coincide with the vehicle entering « limp mode, » where power is restricted to prevent damage.

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Most likely causes of trouble code P0718

This diagnostic trouble code can stem from various issues. Here are the most common causes, ranked from most to least probable:

1. Faulty Input/Turbine Speed Sensor « A » – The sensor itself may be defective, worn out, or damaged, leading to inconsistent signals.
2. Damaged or corroded wiring and connectors – Electrical connections that are frayed, corroded, or loosely connected can cause intermittent signals.
3. Short circuits or open circuits in the sensor circuit – Shorted wires or broken wiring insulation may disrupt proper communication.
4. Transmission control module (TCM) malfunction – Although less common, issues with the TCM can misinterpret sensor signals or generate false faults.
5. Internal transmission issues – Rarely, internal transmission failures affecting the turbine speed signal path.

*Note:* Identifying the exact cause generally requires systematic diagnostics, starting with visual inspections and live data analysis.

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How to diagnose trouble code P0718

Diagnosing P0718 requires a methodical approach to confirm the fault’s origin:

1. Visual Inspection: Check the wiring harness connected to the Input/Turbine Speed Sensor « A » for fraying, corrosion, or damage. Examine connector integrity and cleanliness.
2. Retrieve Live Data: Using a compatible scan tool, monitor the sensor signal while the vehicle is running. Look for irregularities or dropouts.
3. Test Sensor Resistance: Disconnect the sensor and measure resistance across its terminals according to the manufacturer’s specifications.
4. Check Circuit Continuity: Perform continuity tests on wiring harnesses to ensure there are no open circuits.
5. Inspect Related Components: Verify the condition of the transmission control module wiring, grounds, and power supplies.
6. Scan for Additional Codes: Other related transmission fault codes can provide clues for diagnosis.
7. Perform Functional Tests: If permissible, replace the sensor temporarily with a known good unit to confirm if the fault clears.

*Note:* Always follow safety procedures and manufacturer-specific diagnostic procedures.

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Possible repairs for trouble code P0718

Based on the identified cause, repairs may involve:

– Replacing the faulty **Input/Turbine Speed Sensor « A »** – This is often a **basic repair** suitable for a trained DIYer.
– Repairing or replacing damaged **wire harnesses or connectors** – A **moderate repair** requiring electrical knowledge.
– Clearing wiring issues like **corrosion or loose connections** – Typically straightforward.
– Updating or reprogramming the **Transmission Control Module** if malfunctioning – Usually a **professional task**.
– Addressing underlying transmission issues if internal faults are identified – This ranges from component replacement to complete transmission overhaul and requires expert intervention.

*It is essential to identify the root cause accurately before replacing parts to avoid unnecessary repairs.*

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Vehicles commonly associated with trouble code P0718 in Europe

This code can appear across various makes and models, especially those with electronically controlled transmissions. In Europe, common vehicle brands linked to this fault include:

– **Volkswagen Group** (e.g., VW Golf, Audi A3, Skoda Octavia)
– **Ford** (e.g., Fiesta, Focus)
– **BMW / Mini**
– **Hyundai/Kia** (e.g., i30, Sportage)
– **Mercedes-Benz** (various models with automatic transmissions)

The frequency of occurrence varies depending on vehicle age, mileage, and maintenance history. Be sure to cross-reference specific vehicle models with published repair data.

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Frequent mistakes with trouble code P0718

When diagnosing or repairing P0718, technicians and vehicle owners often make several errors:

– Overlooking wiring and connector issues; fixing the sensor without inspecting the wiring can result in recurring faults.
– Replacing the sensor without live data verification, leading to unnecessary part replacements.
– Ignoring related transmission problems that could influence sensor readings.
– Neglecting to clear DTCs after repairs, which can cause false reoccurrence of the code.
– Failing to follow manufacturer-specific diagnostic procedures can lead to misdiagnosis or incomplete repairs.

Ensuring a comprehensive diagnosis before component replacement saves both time and money, minimizes unnecessary parts fitting, and restores vehicle reliability.

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FAQ — trouble code P0718

**Can this code disappear on its own?**
Answer: Unlikely. While some electrical glitches can be temporary, persistent P0718 signals typically require repair or component replacement.

**Can I keep driving?**
Answer: Yes, but cautiously. If the vehicle exhibits shifting problems or warning lights, it is advisable to have it checked promptly. Extended driving with this fault may risk further transmission damage.

**Why does the code return after clearing?**
Answer: Because the underlying issue remains unresolved. The sensor or its circuitry continues to send faulty signals, triggering the fault to reappear after reset.

**Is this a serious problem?**
Answer: It can become serious if ignored. Immediate diagnosis and repair prevent potential transmission damage and costly repairs down the line.

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This comprehensive diagnostic sheet aims to provide clarity and confidence when dealing with the P0718 fault. Always follow manufacturer specifications and consult professional technicians for complex repair procedures.

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