2012 Nissan Sentra Speed Sensor Location

The 2012 Nissan Sentra, while not exactly a performance icon, is a reliable and practical compact car. Maintaining its optimal function requires attention to various components, and the speed sensors play a crucial role. Knowing the location of these sensors is essential for diagnostics, repair, and replacement. This article provides a detailed guide to locating the speed sensors on a 2012 Nissan Sentra, covering both the input (transmission) and output (wheel) speed sensors.

Understanding Speed Sensors in the 2012 Nissan Sentra

Before diving into the location specifics, it's important to understand the function of speed sensors in the 2012 Sentra. These sensors are integral to several vehicle systems, including the:

Transmission Control Module (TCM): The TCM uses input and output speed sensor data to determine shift points and ensure smooth gear changes in automatic transmissions.
Anti-lock Braking System (ABS): Wheel speed sensors provide data to the ABS module to prevent wheel lockup during braking, enhancing safety.
Electronic Stability Control (ESC): If equipped, the ESC system uses wheel speed data to detect and prevent skidding.
Speedometer and Odometer: The vehicle speed displayed on the speedometer and the distance recorded by the odometer rely on speed sensor readings.

A faulty speed sensor can lead to a range of problems, including erratic shifting, ABS malfunction, speedometer inaccuracies, and illumination of the check engine light. Diagnostic Trouble Codes (DTCs) like P0500 (Vehicle Speed Sensor A Malfunction), P0720 (Output Speed Sensor Circuit Malfunction), and related codes can point to speed sensor issues.

Locating the Input (Transmission) Speed Sensor

The input speed sensor, also referred to as the transmission speed sensor, is typically located on the transmission housing. It monitors the speed of the input shaft inside the transmission. On the 2012 Nissan Sentra, the procedure for locating it is as follows:

Vehicle Preparation: Safely lift the vehicle using a jack and jack stands. Ensure the vehicle is stable and secure before proceeding. Work on a level surface.
Identifying the Transmission: Locate the transmission housing. It's situated between the engine and the drive axles.
Sensor Location: The input speed sensor is usually found on the side or top of the transmission casing. It is typically secured with a single bolt or screw. Look for a sensor with a wire harness connected to it. The 2012 Sentra, equipped with a Continuously Variable Transmission (CVT), will have the sensor mounted on the CVT housing. Consult a repair manual specific to the CVT model for exact placement.
Visual Inspection: Once located, visually inspect the sensor and its wiring harness for any signs of damage, such as cracks, frayed wires, or corrosion.

Important Note: Access to the input speed sensor might be restricted by other components. You may need to remove air intake ducts or other parts to gain better visibility and access. Refer to the 2012 Nissan Sentra repair manual for detailed removal instructions.

Locating the Output (Wheel) Speed Sensors

The 2012 Nissan Sentra, equipped with ABS, has wheel speed sensors at each wheel hub. These sensors monitor the rotational speed of each wheel. The location is generally consistent across all four wheels.

Wheel Access: For each wheel, safely lift the vehicle and remove the wheel. Use a jack and jack stands, and ensure the vehicle is properly supported.
Sensor Location: The wheel speed sensor is typically mounted on the steering knuckle or hub assembly, positioned close to the brake rotor. It uses a tone ring (a toothed ring) mounted on the wheel hub to generate a signal.
Visual Identification: The sensor is usually held in place by a bolt or screw. A wire harness connects the sensor to the ABS control module. The sensor itself often has a cylindrical shape.
Front Wheel Speed Sensors: On the front wheels, the sensor is usually integrated into the wheel bearing hub assembly.
Rear Wheel Speed Sensors: On the rear wheels, the sensor is typically bolted onto the rear hub assembly near the axle.
Inspecting the Tone Ring: While you are there, closely inspect the tone ring for damage, cracks, or excessive rust. A damaged tone ring can cause inaccurate speed readings.

Important Considerations for Wheel Speed Sensors:

Sensor Type: Wheel speed sensors can be of two main types: inductive and Hall-effect. Inductive sensors generate an AC voltage signal, while Hall-effect sensors produce a digital signal. The 2012 Sentra typically uses Hall-effect sensors.
Wiring Harness Routing: Pay close attention to the routing of the wiring harness. Ensure it is not pinched, stretched, or rubbing against any moving parts.
Corrosion: Wheel speed sensors are exposed to harsh environmental conditions, making them susceptible to corrosion. Clean any corrosion from the sensor and connector before reinstalling.

Diagnostic Tips and Troubleshooting

When diagnosing speed sensor problems on a 2012 Nissan Sentra, consider the following:

Scan for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to retrieve any stored DTCs related to speed sensors. Common codes include P0500, P0720, C1101, C1102, C1103, and C1104 (specific to each wheel).
Live Data Monitoring: Use the scanner to monitor live data from the speed sensors while driving. Compare the readings from each sensor to identify any discrepancies.
Wiring Harness Inspection: Carefully inspect the wiring harness for any signs of damage, such as breaks, shorts, or corrosion. Use a multimeter to check for continuity and voltage.
Sensor Testing: Use a multimeter or oscilloscope to test the sensor's output signal. Consult the repair manual for the proper testing procedure and specifications. For a Hall-effect sensor, you'll typically see a digital square wave signal when the wheel is rotating.
Tone Ring Inspection: Ensure the tone ring is clean and free of damage. Even a small crack or missing tooth can cause erratic readings.
Bearing Inspection: If the wheel speed sensor is integrated into the wheel bearing, check the bearing for excessive play or noise. A worn bearing can affect the sensor's performance.

Real-World Example: A 2012 Nissan Sentra owner experienced erratic shifting and the ABS light illuminated. Scanning the vehicle revealed a code for the right rear wheel speed sensor. Upon inspection, the mechanic found that the wiring harness had been damaged by road debris. Repairing the wiring harness resolved the problem.

Replacing Speed Sensors

If a speed sensor is found to be faulty, replacement is usually the best course of action. Here's a general overview of the replacement procedure:

Disconnect the Battery: Disconnect the negative battery cable to prevent electrical shorts.
Remove the Wheel (for Wheel Speed Sensors): If replacing a wheel speed sensor, remove the wheel.
Disconnect the Wiring Harness: Carefully disconnect the wiring harness from the sensor.
Remove the Sensor: Remove the bolt or screw securing the sensor. Gently pull the sensor out of its mounting hole. If the sensor is stuck, use a penetrating lubricant.
Install the New Sensor: Install the new sensor, ensuring it is properly seated. Tighten the mounting bolt or screw to the specified torque.
Connect the Wiring Harness: Connect the wiring harness to the new sensor.
Reinstall the Wheel (for Wheel Speed Sensors): Reinstall the wheel and torque the lug nuts to the specified torque.
Reconnect the Battery: Reconnect the negative battery cable.
Clear DTCs: Use a scan tool to clear any DTCs that may have been stored.
Test Drive: Test drive the vehicle to verify that the problem has been resolved.

Important Note: When replacing wheel speed sensors, always use a quality replacement part from a reputable supplier. Using a low-quality sensor can lead to inaccurate readings and further problems.

Conclusion

Locating the speed sensors on a 2012 Nissan Sentra is a crucial step in diagnosing and repairing issues related to transmission performance, ABS, and other vehicle systems. By understanding the location of both the input (transmission) and output (wheel) speed sensors, and by following the diagnostic and replacement procedures outlined in this article, you can effectively address speed sensor problems and keep your 2012 Sentra running smoothly. Remember to always consult the official 2012 Nissan Sentra repair manual for specific instructions and torque specifications.