Testing your Subaru VSS: A Comprehensive Guide

If you’re a Subaru owner, you may have experienced issues with your vehicle’s speedometer or cruise control. This could be a sign of a faulty Vehicle Speed Sensor (VSS). In this article, we’ll go over everything you need to know about testing your Subaru VSS and fixing any issues that may arise.

What is a VSS and how does it work?

A Vehicle Speed Sensor (VSS) is a sensor that monitors the rotation of the transmission. It measures the speed at which a vehicle is traveling, sending that information to the Engine Control Module (ECM), which then adjusts engine functions such as ignition, transmission shifting, and cruise control. Without a functioning VSS, the speedometer, odometer, and cruise control won’t work properly.

There are two types of VSS: magnetic and hall-effect. The magnetic VSS creates an AC voltage that increases with speed, while the hall-effect VSS creates a digital signal. Most Subaru models use the hall-effect VSS.

Signs of a faulty VSS

A faulty VSS can cause various issues with your vehicle. Here are some signs of a problematic VSS:

  • The speedometer may fluctuate or stop working altogether.
  • The cruise control may stop functioning.
  • The Check Engine Light (CEL) may turn on.
  • The transmission may shift erratically.
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How to test your Subaru VSS

Testing your Subaru VSS is a simple process that can help you avoid costly repairs. Here are the steps to follow:

Step 1: Preparation

Before getting started, make sure you have the following tools:

  • A multimeter
  • A jack and jack stand or ramps
  • Electrical contact cleaner
  • A helper (optional)

Step 2: Locate the VSS

The VSS is located on the transmission output shaft housing. Refer to your vehicle’s owner’s manual or a repair manual to locate it.

Step 3: Disconnect the VSS

Using a wrench or socket set, remove the bolt that secures the VSS to the transmission housing. Then, disconnect the electrical connector from the VSS.

Step 4: Test the VSS with a multimeter

Set your multimeter to measure resistance (ohms). Place the positive lead on the terminal of the VSS, and the negative lead on the body of the VSS or a good ground. The resistance should be within the range specified by your vehicle’s manufacturer. If the resistance is out of range, the VSS is faulty and needs to be replaced.

Step 5: Inspect the VSS

Visually inspect the VSS for damage, such as rust, corrosion, or cracks. If you see any damage, replace the VSS.

Step 6: Clean the electrical contacts

If the resistance is within range and there’s no visible damage to the VSS, the issue may be with the electrical contacts. Use electrical contact cleaner to clean the contacts on both the VSS and the electrical connector. Reconnect the VSS and test the system again.

Common VSS problems

The most common problem with the VSS is dirt or debris getting stuck between the sensor and the tone ring, which can cause the signal to be erratic. This can be fixed by cleaning the area around the VSS and removing any debris.

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Another common issue is a damaged tone ring, which can cause the VSS to fail. This requires a complete transmission overhaul, as the tone ring is built into the transmission.

DIY replacement of a faulty VSS

If you’ve determined that your VSS is faulty and needs to be replaced, you can DIY the replacement process to save on labor costs. Here are the steps to follow:

  1. Disconnect the negative battery cable.
  2. Raise the vehicle using a jack and jack stand or ramps.
  3. Locate the VSS and disconnect it as described in step 3 of the testing process.
  4. Remove the bolts that secure the VSS to the transmission housing.
  5. Install the new VSS and secure it with the bolts.
  6. Reconnect the electrical connector to the VSS.
  7. Lower the vehicle and reconnect the negative battery cable.


Q: What happens if I don’t replace a faulty VSS?

A: If you don’t replace a faulty VSS, it can cause various issues with your vehicle’s speedometer, cruise control, and transmission shifting. It can also cause your vehicle to fail emissions tests and result in expensive repairs down the road.

Q: Can I drive with a faulty VSS?

A: It’s not recommended to drive with a faulty VSS as it can cause issues with your vehicle’s performance and safety.


Testing your Subaru VSS is an easy process that can help you avoid costly repairs. By following the steps outlined in this article, you can diagnose and fix any issues with your VSS on your own. Remember to always refer to your vehicle’s owner’s manual or a repair manual for specific instructions on your vehicle. Happy troubleshooting!

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Billy Covington

With a passion for all things automotive, Billy is our go-to expert on Subaru performance upgrades and modifications. He's been featured in several car magazines and blogs, and his extensive knowledge and expertise make him a valuable member of our team. When he's not working on cars, he enjoys playing guitar and writing music.

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