P0718
UniversalInput/Turbine Speed Sensor Circuit Intermittent
Medium SeverityThe P0718 code indicates that the transmission control module (TCM) is receiving an intermittent signal from the input/turbine speed sensor. This intermittency can prevent the transmission from shifting correctly, leading to unpredictable driving behavior.
⚠️ Before You Begin (Safety First)
Always practice safe automotive repair procedures. Before working on any electrical components, always disconnect the battery's negative terminal to prevent accidental shorts or shocks. Allow hot components to cool before touching. Wear appropriate personal protective equipment, including safety glasses and gloves.
Common Symptoms
- Check Engine Light illuminated
- Erratic or harsh shifting
- Transmission slipping or not engaging gears
- Vehicle entering 'limp mode'
- Lack of power or poor acceleration
- Transmission may get stuck in one gear
Common Causes
- Faulty or intermittently failing input/turbine speed sensor
- Damaged or frayed wiring in the sensor circuit
- Corroded or loose electrical connectors at the sensor or Transmission Control Module (TCM)
- Internal transmission fluid contamination affecting sensor readings
- Rarely, a failing Transmission Control Module (TCM)
Frequently reported on: Ford F-150 (2004-2010), Chevrolet Silverado (2000-2006), Honda Accord (2003-2007), Toyota Camry (2002-2006)
Diagnostic Steps
- Check transmission fluid level and condition. Low or contaminated fluid can cause shifting issues.
- Visually inspect the input/turbine speed sensor wiring and connector for damage, corrosion, or looseness. Repair or clean as necessary.
- Locate the input/turbine speed sensor (often on the transmission housing) and carefully remove it.
- Test the old sensor's resistance with a multimeter, comparing it to manufacturer specifications. An intermittent or out-of-spec reading indicates a faulty sensor.
- Install a new input/turbine speed sensor, ensuring the connector is securely attached. If applicable, replace the sensor O-ring.
- Clear the P0718 code using an OBD-II scanner and test drive the vehicle to confirm the repair.
👨🔧 When to Call a Professional
If you have replaced the sensor and checked the wiring, and the P0718 code or transmission shifting issues persist, it is time to consult a professional. Intermittent circuit issues can be challenging to diagnose and may point to internal transmission problems or complex wiring harness faults within the transmission itself that require specialized diagnostic tools.
Commonly Asked Questions
What does an intermittent signal mean for the speed sensor?
An intermittent signal means the sensor is sometimes sending data correctly and sometimes not. This can be caused by a loose connection, frayed wire, or the sensor itself failing internally, leading to inconsistent transmission performance.
Can I drive with a P0718 code?
While the car may still drive, it is not recommended to drive for an extended period. Erratic shifting or limp mode can be dangerous, and continuing to drive with an untreated transmission issue could lead to more severe and costly transmission damage.
Where is the input/turbine speed sensor located?
The input/turbine speed sensor is typically located on the transmission case, often near the bell housing or directly on the transmission body. Its exact location varies by vehicle make and model.
Is it possible for a dirty transmission fluid to cause a P0718 code?
Yes, dirty or low transmission fluid can indirectly contribute to speed sensor issues or cause similar symptoms. Debris in the fluid can interfere with sensor operation, and low fluid can cause incorrect pressure, affecting sensor readings. Always ensure fluid is at the correct level and clean.
What's the difference between an input and output speed sensor?
The input (or turbine) speed sensor measures the rotational speed of the transmission's input shaft, which is directly related to engine speed. The output speed sensor measures the speed of the transmission's output shaft, which is related to vehicle speed. Both are crucial for the TCM to accurately determine gear ratios and shift points.