Why My Speedometer Not Working? (11 Reasons Why)

Your car has a speedometer, right? So you’ll notice when you’re stopped at a light and see if your speed is close to the limit. But afterward, you’ll realize it’s not working!

Is it because you’re going the wrong way or can’t remember how fast you drove? Well, don’t take these little errors for granted! Here’s what we’re going to uncover about why your speedometer malfunctions!

Why My Speedometer Not Working?

Your speedometer won’t work if there’s a faulty speed sensor, which occurs if something gets caught under the sensor lever. If a speed sensor wiring has been damaged, causing a short circuit, your speedometer will malfunction. In some cases, your engine control unit, with some of its most advanced electronics, can experience internal glitches over time. 

Let’s get ready to identify the causes of why your speedometer is unreliable, so keep reading!

1. Faulty Speed Sensor

A speedometer is a vital part of a car’s instrument panel; it measures the distance you travel in one mile and can also indicate how fast you’re traveling.

Meanwhile, a malfunctioning speed sensor will consequently have an immediate effect on how an automatic transmission operates.

As well as that, a strange automatic gearbox operation is one of the most prevalent warning indications of a defective speed sensor.

As a result, the transmission may display symptoms such as delayed shifts and restricted gear usage if the VSS malfunctions, leading to erroneous readings on your speedometer.

2. Busted Speed Sensor Wirings

A broken speed sensor wiring is a common problem when your speedometer starts to malfunction.

That said, it might be due to an interrupted electrical circuit from the engine to the speedometer.

Besides that, although driving without a functioning vehicle speed sensor is technically feasible, it is strongly advised against doing so.

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Overall, a busted speed sensor wiring will lessen the detection of how fast you’re driving and reduce sending a signal to the speedometer in your car.

3. Deficient Engine Control Unit

If your speedometer is not working, you may need to look at the engine control unit (ECU).

With that, a malfunctioning speedometer has issues with its internal electronics. These components are expensive and should be replaced as soon as possible if damaged or broken.

Apart from this, for the ECU to operate, the electronic cells in car batteries must be functional. Your vehicle’s ECU will soon fail if any of the battery’s cells are dead.

Therefore, if there are problems with this component, they can cause issues with the speedometer.

4. Malfunctioning Instrument Cluster

Instrument clusters are electronic devices that control the operation of various car parts, such as headlights and other accessories.

Additionally, the instrument cluster may cease operating if the voltage regulator that supplies electricity to the instrument panel is defective.

As well as that, this can be caused by a loose or missing sensor or even a crack in the glass. Above all, if your instrument cluster is broken, it will not register your actual speed.

5. Electrical Shortage

As mentioned above, a speedometer sends electrical signals through the vehicle’s wiring system to the dashboard display.

Because of that, the mechanical system in your car uses electricity to run its various components.

Thus, the electrical system can suffer from a power shortage if insufficient juice is unavailable.

Furthermore, this could be caused by a battery needing replacement or an issue with the alternator.

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For that reason, if there is an electrical shortage with the wiring system, it will be reflected in the speedometer display.

6. Dashboard Malfunctions

Dashboard Malfunctions

Another common problem with a defective speedometer may be a problem with the dashboard itself.

As we all know, the dashboard is the box that attaches to your windshield and holds all of the buttons and knobs that allow you to control your car’s auxiliary functions.

In most cases, a blown fuse could cause your dashboard to go out. But, it can also be the result of deeper electrical problems.

As a consequence, issues with a loose ground wire are causing an error code to display on your dashboard.

7. Blown Fuse

A blown fuse can be caused by an electrical short, which can happen if you have a loose connection in your battery or electrical system.

As a result, the wiring in your car may eventually become visible due to the fraying of this insulation and contact with your car’s metal engine parts or frame.

Inevitably, most cars have one fuse that keeps all their electrical subsystems running, and if that fuse blows, your vehicle will be inoperable, including your speedometer.

8. Wavering Speedometer Needle

A speedometer should move smoothly when the car accelerates or decelerates. However, the speedometer does occasionally sway or move abruptly.

When this occurs, the speedometer wire needle inside the transmission is typically to blame for delivering the speedometer erroneous data.

As it happens, and the speedometer needle is damaged, the speedometer will fluctuate by ten miles per hour.

9. Failing Fuel Gauge

A damaged fuel gauge sender could make the gauge move unexpectedly or read incorrectly.

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Additionally, when one gauge stops working, the issue might be with the gauge itself, but when all the gauges stop operating, it usually means a fuse has occurred.

Therefore, all these components are interconnected and are a potential factor that leads to a faulty speedometer.

10. Defective Tachometer

A tachometer measures engine RPMs and provides information to the car’s computer about how fast the engine runs.

Under some circumstances, poor wiring may also cause an unreliable tachometer. For example, if you receive inconsistent readings, they can point to faulty cable wiring.

Considering that your speedometer isn’t functioning, the tachometer may be the source of its insufficiency.

11. Old Vehicle

When a vehicle ages, its parts wear down and eventually need to be replaced.

In some cases, if you have a new car and the speedometer isn’t working, it’s possible there was an error in manufacturing. Naturally, the same goes for older cars.

Therefore, if you have more than one problem with your speedometer, it’s likely time to replace the entire unit.

To know more, you can also read our posts on why your coolant is not circulating, why your car won’t start with a new battery, and why your car won’t jumpstart.


Speedometers are very important in car safety because they help drivers know whether they are going too fast or if they are too slow.

As we’ve found out, a defective speed sensor, damaged speed wire, and a defective engine control unit all contribute to your speedometer’s shortcomings.

Ultimately, it’s essential to keep an eye on this device since it can tell you how fast you’re going and help you navigate safely!

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