P0718 — Input/Turbine Speed Sensor “A” Circuit Intermittent #

Note: The code description may vary depending on the vehicle manufacturer.

• Input/Turbine Speed Sensor “A” Circuit Intermittent (General/SAE)
• Input Speed Sensor Intermittent Signal (Chrysler, Dodge, Jeep, RAM)
• Turbine Speed Sensor A Circuit Intermittent (GM, Ford, Honda, Toyota, Nissan)
• Transmission Input Speed Sensor Circuit Intermittent (Hyundai, Kia)

Summary of Code P0718 #

P0718 is a diagnostic trouble code (DTC) that indicates an intermittent electrical issue detected by the vehicle’s powertrain control module (PCM) or transmission control module (TCM) in the Input/Turbine Speed Sensor “A” circuit. This sensor monitors how fast the transmission’s input shaft is spinning, helping the computer determine if the transmission is working as intended. When the signal from this sensor drops in and out unexpectedly, the system triggers code P0718. An intermittent signal can cause erratic transmission behavior and may impact drivability or shifting quality. Understanding and addressing this code promptly can prevent further transmission damage.

Common Symptoms for Code P0718 #

When the P0718 code is stored, you may notice several symptoms—some subtle, others more obvious. Because the input/turbine speed sensor is crucial for shift timing and overall transmission operation, even an intermittent fault can result in unpredictable driving characteristics. Here’s what you might experience:

• Harsh, delayed, or erratic shifting
• Transmission stuck in “limp” mode (staying in one gear)
• Illuminated Check Engine Light (CEL) or Transmission Warning Light
• Reduced fuel efficiency
• Speedometer or gear indicator irregularities
• Possible engine stalling when coming to a stop

Probable Causes for Code P0718 #

The P0718 code typically results from issues that interrupt the electrical signal between the input/turbine speed sensor and the vehicle’s control module. Based on field experience, the most frequent causes are:

1. Faulty Input/Turbine Speed Sensor “A” — The sensor itself may have an internal fault or intermittent connection.
2. Damaged or corroded wiring/connectors — Wires or plugs may have damage, corrosion, loose terminals, or broken insulation.
3. Poor electrical ground — A weak or intermittent ground connection can disrupt sensor signal integrity.
4. Transmission fluid contamination — Excess debris or water in the fluid can affect sensor readings, especially if the sensor is magnetic.
5. Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM) — Rarely, the root cause could be a failing control unit.

Step-by-Step Diagnosis for Code P0718 #

Diagnosing an intermittent electrical code like P0718 requires patience and methodical troubleshooting. Here’s a proven approach:

• 1. Scan for codes and freeze frame data: Use an OBD-II/EOBD scanner to confirm the presence of P0718 and note when it sets.
• 2. Visual inspection: Carefully inspect the input/turbine speed sensor and related wiring harness for signs of damage, corrosion, or loose connections.
• 3. Wiggle test: With the engine running, gently move the harness and connectors to see if the code resets or the sensor signal fluctuates.
• 4. Check sensor resistance and signal: Use a multimeter to measure the sensor’s resistance (refer to OEM specs) and monitor output while spinning the input shaft (if possible).
• 5. Inspect grounds and power supply: Verify that the sensor’s ground and 5V reference (if used) are solid and within specifications.
• 6. Check for transmission fluid contamination: Inspect the fluid for debris or excessive metal particles, which could affect a magnetic sensor.
• 7. Test the circuit from the sensor to the PCM/TCM: Ensure continuity and absence of shorts or opens using wiring diagrams.
• 8. Substitute with a known-good sensor: If possible, swap the sensor to confirm if the fault is resolved.
• 9. Check control module operation: As a last resort, suspect the PCM or TCM only if all other checks pass.

Possible Repairs for Code P0718 #

Once the root cause is identified, targeted repairs can be performed. The most common solutions include:

• Replace the input/turbine speed sensor “A” if it’s confirmed faulty or inconsistent.
• Repair or replace damaged wiring/connectors to restore proper electrical continuity.
• Clean or secure sensor ground connections to ensure a stable signal path.
• Flush and replace contaminated transmission fluid if debris is affecting sensor performance.
• Update or reprogram the PCM/TCM if a software update from the OEM addresses the issue.
• Replace the PCM/TCM only if all other solutions fail and control module failure is confirmed.

Is It Safe to Drive with Code P0718? #

Limited. While your vehicle may still be drivable with code P0718 present, it’s not recommended to ignore it. Intermittent input/turbine speed sensor signals can cause unpredictable shifting, “limp” mode, and even sudden loss of power. Prolonged driving under these conditions can lead to further transmission damage or unsafe driving situations. For your safety and to avoid costly repairs, address this issue as soon as possible.

Vehicles Most Commonly Affected by Code P0718 #

While P0718 can appear on any OBD-II compliant vehicle, it’s more frequently reported on certain makes and models, especially those with automatic transmissions using magnetic or hall-effect input speed sensors. Based on repair data, vehicles often affected include:

• Chrysler, Dodge, Jeep, RAM (especially 2000s–2010s models)
• GM (Chevrolet, GMC, Buick, Cadillac, especially mid-2000s and newer)
• Ford (Fusion, Focus, Escape, F-150, etc.)
• Honda/Acura (Accord, Odyssey, Pilot)
• Toyota/Lexus (Camry, Corolla, RAV4, Highlander)
• Nissan/Infiniti (Altima, Maxima, Pathfinder)
• Hyundai/Kia (Sonata, Santa Fe, Optima, Sorento)

Common Mistakes & Best Practices for Code P0718 #

Solving P0718 can be straightforward with careful diagnosis, but there are some pitfalls to avoid. Here are the most common mistakes — and best practices smarter technicians follow:

• Mistaking wiring issues for sensor failure: Always inspect and test the wiring and connectors before replacing the sensor.
• Skipping the wiggle test: Intermittent codes often reveal themselves when you manipulate the harness during testing.
• Ignoring transmission fluid condition: Dirty or contaminated fluid can impact sensor performance, especially in high-mileage vehicles.
• Failing to clear codes and retest: Always erase stored codes after repair and verify the fix with a road test.
• Overlooking TSBs (Technical Service Bulletins): Always check OEM bulletins for known issues or updates related to this code.

Express FAQ for Code P0718 #

Here are quick answers to the most common questions about this trouble code:

• Q: Is replacing the speed sensor difficult?
  A: On most vehicles, the input/turbine speed sensor is accessible from outside the transmission and can be changed with basic tools in under an hour. Some models, however, may require partial transmission disassembly.
• Q: Can low transmission fluid trigger P0718?
  A: Low fluid levels can cause erratic transmission operation, but P0718 specifically refers to an electrical issue with the sensor circuit. Always check fluid level and condition during diagnosis.
• Q: Will clearing the code fix the problem?
  A: Clearing the code without addressing the root cause will only result in the code returning. Proper diagnosis and repair are necessary for a permanent fix.

Need further help? Consult your vehicle’s service manual or an experienced technician for detailed wiring diagrams and OEM-specific procedures. Early intervention can save your transmission—and your wallet!