Bad Speed Sensor Symptoms and How to Fix a Broken Speed Sensor

Your car’s speed sensor serves various purposes. One of these is that it transmits the signals to your speedometer – the instruments that indicate the speed of your car when accelerating. Another thing is that the speed sensor controls the ignition timing and fuel flow. The same car component is responsible for cruise control.

As you can see, the speed sensor is so important given what it does to your car. In line with this, many things can tell that your speed sensor is no longer working properly. For this post, let me tell you more about the speed sensor, its job, the problems it can cause once you got it broken, and the best way to fix it.

What Does A Transmission Speed Sensor Do?

The VSS or vehicle speed sensor, also called transmission speed sensor, is the tiny device mounted on your car transmission. As I said before, its main function is to measure the speed of your car through the twisting toothed wheel that you will find in the shaft within the transmission.

The transmission speed sensor generates low voltage indicators. If your speed sensor is in trouble, the speedometer operation is not the only that will suffer because the transmission and engine control systems also depend on the data generated by the speed sensor. These two systems work together with the VSS to come up with needed changes that will allow your car to run smoothly and efficiently.

Based on my observations and experience, some other systems can also suffer when the speed sensor is not okay. One of these is the cruise control that also uses the data the speed sensor creates.

Bad Speed Sensor Symptoms

How Do I Know If My Speed Sensor Is Bad?

If your speed sensor is having a problem, you can confirm it by checking your car for these 4 common transmission speed sensor symptoms:

Malfunctioned Cruise Control

The speed sensor of your car has to remain efficient and functional to ensure the efficiency of your cruise control system. If your motor control unit is not receiving the correct data regarding your car’s speed rate, the cruise control system will also fail to generate and sustain your preferred speed.

Your car engine control system cannot detect the issue. Instead, it will just prevent you from using cruise control until the issue is repaired. Let’s say you’re not using the cruise control system each time you drive. If that is the case and you feel the speed sensor is broken, I suggest you test them by trying to use the cruise control system and find out.

Check Engine Light

Seeing the “check engine light” flashing does not always pertain to a damaged speed sensor because it can also mean more things. However, if you already noticed a faulty cruise control coupled with the illuminating check engine light indicator, the problem is no doubt a broken speed sensor.

The data that the speed control provides is more important to your engine control system. If it doesn’t receive accurate information, the engine control system will inform you of the issue by turning on the check engine light.

Related: How to disable check engine light permanently

As the speed sensor is unable to generate the necessary data, the PCM will fail to effectively control the shifting motion of the gears inside the transmission system. In this case, the transmission may shift jaggedly or faster than it should. A broken speed sensor can also affect the right shift timing that changes the interval between the shifts.

Automatic transmissions are hydraulically managed and expected to shift flawlessly. Bad transmission shifting can damage the internal components like hydraulic lines, valve bodies, and mechanical gears. Get in touch with someone like me once you detected any transmission shifting issues.

Disabled Torque Converter Grip

Your car’s torque converter grip starts working at the pre-programmed speed. If the speed sensor is not able to produce the needed accurate information, then it will mean the torque converter cannot apply the needed clutch and create the mechanical connection between the transmission and engine systems. It can cause decreased fuel economy, slipping, and overheated transmission.

Read 7 Slipping Clutch Symptoms

Can I Drive with A Bad Transmission Speed Sensor?

A damage speed sensor can make driving unsafe. Failure to get it fixed right away puts your car and your safety at stake.

How to Test Your VSS?

Once you notice any of those symptoms I mentioned, you must bring your car to the local auto repair shop. In dealing with a suspected broken speed sensor, I run a PC diagnostic test on the car for proper diagnosis. As some issues associated with the speed sensor are relevant to transmission, the best thing to do is to consult a car repair shop in your area before heading to specialty repair shops.

How to Fix a Broken Speed Sensor

By default, your car comes with a vehicle speed sensor. In the long run, this sensor will fail and cause a myriad of problems in your car. Don’t worry. I’ll be giving you the steps to follow in repairing a damaged speed sensor.

Items Needed:

  • Wrench
  • Jacks
  • Replacement speed sensor
  • Directions:

    Park your car on a good, level surface. Engage your emergency brake, then switch off the engine. If you just used the car, let it rest for up to 30 minutes. Start working on it when the components are already cool.

    Put the car jack on your car’s left and right sides. Lift the vehicle jacks until there’s sufficient room that will allow you to go underneath your car. Slide under the car while lying on your back.

    Start checking your car’s passenger side where you’ll find the transmission system. The one that sits on its right is the vehicle speed sensor. It is the little plug-type part that comes out sideways. The VSS is roughly 3” long and features an electric connector that comes straight out of it.

    Unplug the electric wire. Pull the wire connector’s base directly from the plug. Now, you get easy access to a bolt that keeps the speed sensor intact. With a wrench, start removing the bolt. Turn the wrench counterclockwise to unscrew the damaged speed sensor. Discard it.

    Align the new VSS into your car’s transmission. Screw it in a clockwise motion to attach and tighten. Change the bolt and tauten it to keep the replacement speed sensor in place. Plug the electric base of the speed sensor while waiting for the clicking sound. Glide out from the underside of your car and low the jacks.


    That’s all I can share about dealing with a broken speed sensor. Don’t waste your time. If you feel you can’t fix it alone, it might be better to contact an auto mechanic near you.

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