A Continuously Variable Transmission (CVT) relies on a complex network of sensors to function correctly. These sensors provide crucial data to the Transmission Control Module (TCM), enabling it to adjust the gear ratio seamlessly and optimize performance. Among these sensors, the CVT transmission speed sensors play a vital role. This article delves into the importance of these sensors, common issues, and troubleshooting techniques.
The Importance of CVT Transmission Speed Sensors
CVT transmission speed sensors, often categorized as primary (input) and secondary (output) sensors, monitor the rotational speed of various components within the transmission. The primary sensor typically measures the engine’s crankshaft speed, while the secondary sensor measures the output shaft speed. This data allows the TCM to calculate the appropriate gear ratio for optimal fuel efficiency and power delivery. Malfunctioning sensors can lead to erratic shifting, poor acceleration, reduced fuel economy, and even complete transmission failure.
Common Problems with CVT Transmission Sensors
Several issues can arise with Cvt Transmission Sensors, including:
- Faulty Sensor Signal: A sensor might provide inaccurate or intermittent signals due to internal damage, wear and tear, or contamination. This can manifest as incorrect speed readings, leading to improper gear ratio adjustments.
- Wiring Harness Issues: Damaged or corroded wiring in the sensor harness can disrupt the signal transmission, causing communication errors between the sensor and the TCM.
- Incorrect Air Gap: CVT speed sensors often rely on a specific air gap between the sensor and the rotating component it monitors. An incorrect air gap can lead to inaccurate readings. The JF011E ATSG service manual (pg 116) outlines the proper procedure for setting this clearance. A common value is .040″.
- Non-OEM Sensors: Using aftermarket sensors not specifically designed for the transmission can result in compatibility issues and inaccurate readings. While often cheaper, opting for OEM sensors from manufacturers like Mitsubishi (for models like the Lancer using the JF011E transmission) is often a safer bet.
Troubleshooting CVT Transmission Speed Sensors
Diagnosing CVT transmission sensor problems often involves:
- Diagnostic Trouble Codes (DTCs): Specific DTCs, such as P0500 (Vehicle Speed Sensor Malfunction) and P0720 (Output Speed Sensor Circuit Malfunction), directly indicate issues with speed sensors. Using a diagnostic scanner to read these codes is the first step in troubleshooting.
- Data Logging: Monitoring sensor data using a scan tool can reveal inconsistencies in speed readings. Comparing the primary and secondary sensor values against engine RPM at different speeds (idle, low, mid, high) can pinpoint faulty sensors. For instance, a significant deviation from the expected speed ratio (e.g., 2.34 in some CVT models) indicates a problem. The ABS wheel speed sensors, through back calculation, can also predict the secondary speed to help diagnose issues.
- Visual Inspection: Inspecting the sensor for physical damage, contamination, and proper air gap is crucial. Additionally, examining the wiring harness for damage, corrosion, or loose connections is essential.
- Component Testing: Using a multimeter or oscilloscope, technicians can test the sensor’s resistance and signal output to determine its functionality.
Conclusion
CVT transmission sensors are critical for proper operation and performance. Understanding their role and common problems is essential for effective troubleshooting. By utilizing diagnostic tools, following proper procedures, and prioritizing OEM components, you can ensure the longevity and reliability of your CVT transmission. Always consult the vehicle’s service manual for specific instructions and recommended procedures.
