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Speedometer Accuracy and How It Affects Your Car’s Extended Warranty

BY: Alex Perrone
Close-up of a hand on a steering wheel in a car and a speedometer on the dash

Your vehicle speed is one of the most important metrics you must constantly monitor. Your vehicle’s speedometer showcases your rate in an easy-to-read display to ensure you travel within the speed limit. While most car owners take this for granted, when it becomes inaccurate, it can be quite dangerous to you, your passengers, and other people on the road.

Let’s examine speedometer accuracy and how it affects your car’s extended warranty.

Understanding Speedometer Functionality and Accuracy

While driving, one of the most essential things to remember is to go the speed limit. This is not only for your safety but for others around you as well. While a click glance on your dashboard will quickly show if you are doing the speed limit, many people understand their speedometer functions and whether or not they are accurate.

The primary function of a vehicle’s speedometer is to understand how fast the car is traveling and relay that information to the driver. You may have a mechanical or electronic speedometer, depending on your car’s age or type. Most cars will use a speed sensor to measure the wheel’s rotation and send the speed reading information to your speedometer, which will raise or lower the needle in analog-style gauges or display numerical values digitally in digital gauges.

It also helps the odometer track the actual mileage of the vehicle. The odometer reading shows the number of miles that are on the car. The odometer is next to the car’s speedometer and tachometer; some car manufacturers label it ODO.

The speedometer, sometimes called a speedo, is only as good as the components feeding it the information. So, if your speed sensor is bad, you could get an inaccurate reading on your gauges. Also, if you have installed larger tires, different rear-end gears, or other modifications different from the factory components, you could have a speedometer discrepancy.

This means your vehicle may show you are going 45 miles per hour when you could be going considerably slower or faster. This is why speedometer accuracy is crucial for safety, avoiding speeding tickets, and ensuring you are covered if you have to file for an extended warranty claim.

The Link Between Speedometer Readings and Extended Warranty Claims

An extended warranty or vehicle service contract is designed to give you protection for components that fail on your vehicle due to poor workmanship or construction. Like factory warranties, an extended warranty can cover unexpected breakdowns from faulty parts or parts that fail due to old age. With each extended warranty, there are stipulations on what is covered, what is not covered, and what you must do as a car owner to ensure your car remains in good operating condition.

While many warranties will emphasize keeping up with routine maintenance and keeping your car in overall good condition, one essential function that can affect your extended warranty is speedometer readings. Accurate speedometer readings refer to the speedometer on your dashboard matching the actual speed of your vehicle. Over time or with certain modifications, your vehicle’s speedometer can become inaccurate, leading to other issues on your car.

Misdiagnosis of Vehicle Issues

One of the most important reasons your speedometer needs to be accurate is for the correct diagnosis of vehicle issues. When diagnosing issues on your vehicle, the speed that reads on the speedometer may be used to determine possible problems. If this is off, it can lead to the wrong problems being diagnosed as the issue. This can lead to the underlying issue needing to be addressed, causing further problems with your vehicle.

Impact on Vehicle Performance

Depending on the severity of your speedometer’s inaccuracy, it can lead you to drive significantly over the speed limit. This can put extra strain on your engine and transmission. If an issue were to occur and the warranty company was to determine that the speedometer inaccuracy caused this, you could face a warranty denial on the repair. It can also cause a decrease in fuel mileage as well.

Warranty Claims and Repairs

Speedometer issues could be covered under an extended warranty when the issue of the faulty speedometer results from a manufacturing defect or problem. This would allow it to fall under the extended warranty contract, allowing you to have it repaired with your extended warranty. However, the warranty might not cover the repairs if the speedometer issue is due to external factors like an aftermarket modification or accident damage.

Safety Concerns

The most obvious concern with an inaccurate speedometer is the safety concern. If your speedometer is inaccurate, you could travel too fast for the posted speed limit. This could put you, your passengers, and other drivers at risk for an accident. If these lead to an accident or vehicle damage, the warranty might not cover the damages if they are attributed to negligent driving or unsafe vehicle speed.

Regular Maintenance and Calibration of Speedometers

While there are a few ways to calibrate your speedometer yourself, some vehicles can be calibrated or re-calibrated with tuning software or through the dealership.


One of the easiest ways to keep your speedometer accurate is to ensure all associated components are in good condition. This means ensuring your speedometer, speed sensors, speedometer cables, and all wiring are free from damage and are replaced if they go bad. Usually, a bad speed sensor will trigger a check engine light, alerting you of an issue with the sensor.

Re-Calibrating with Tuning Software

Suppose you have added modifications to your vehicle that will affect the speedometer’s accuracy, such as larger tires or different rear-end gears. In that case, you must use a tuner or tuning software for your speedometer calibration. Handheld tuners can be purchased from aftermarket car part companies. They can be used to reprogram your ECU to account for larger tires, different gearing, and various other modifications.

Re-Calibrating at a Dealership

If you are uncomfortable using a handheld tuner or would rather have a professional recalibrate your speedometer, you can usually take it to a dealership for calibration. A dealership will usually have the tools to recalibrate your vehicle’s PCM to get your speedometer corrected, no matter what modification you have.

What Can Cause Your Speedometer To Be “Off”?

If you suspect your speedometer is off, there could be a few reasons. Let’s look at some of the most common reasons a speedometer might be inaccurate.

Tire Size

Your factory speedometer is calibrated to factory specifications and settings, including your tire size. When you change your tire size, your speedometer must be recalibrated for the new size. This usually happens when you add larger-sized tires to your vehicle.

Gear Ratio Change

You must re-calibrate your speedometer if you have changed the gear ratio in your rear end. With different gears, your drivetrain turns at a different speed, making your speedometer inaccurate. This is usually done on performance vehicles or vehicles that need to tow larger capacities.

Mechanical Issues

Your speedometer might be off due to a mechanical issue such as a bad speed sensor, damaged speedometer cable, or a short in the wires. If you are experiencing speedometer issues and you have not added any aftermarket parts, you should have the system inspected by a professional mechanic.

Aftermarket Modifications

Aftermarket modifications such as larger wheels, tires, and lift kits can all cause your speedometer to become inaccurate. These modifications affect how quickly your wheels turn, which affects your speed sensor readings. Since these are different from factory specifications, your speedometer must be recalibrated.

Navigating Warranty Claims with Speedometer Issues

If you need to make a warranty claim but have speedometer issues, you must verify if the speedometer issue caused the problem you are facing. If so, the next step will be to determine if the speedometer issue was due to a manufacturing defect or from adding aftermarket components.

If it is a manufacturing defect, your extended warranty should cover the repair of the speedometer and the issue it caused. Your extended warranty claim may be denied if it is due to installing aftermarket parts or neglecting regularly scheduled maintenance. This is why keeping your speedometer and related components in good condition is important. It is also important to recalibrate your speedometer if you have installed any aftermarket components that can affect your speedometer’s accuracy.

The Role of Accurate Record-Keeping In Upholding Extended Warranties

If you have an extended warranty, keeping a detailed record of all the maintenance jobs, repairs, and modifications you have made to your vehicle is essential. Since an extended warranty only covers manufactured defects on the items listed in your service contract, you may need to provide details of how you have kept up with maintenance and what modifications have been made to the vehicle.

The more records you have, the easier it is for you to make a warranty claim. For example, suppose you have added larger wheels and tires and had the speedometer recalibrated. In that case, it will be easier to inform your extended warranty company that you have maintained your speedometer accuracy if there is an issue later.

Keeping Your Vehicle Protected with an Extended Warranty

You should invest in an extended warranty to protect your vehicle from manufactured defects with your speedometer or issues caused by these defects. An extended warranty or vehicle service contract, such as one from Endurance, can give you factory warranty-like coverage to ensure you are covered from unexpected breakdowns.

At Endurance Warranty, we offer a range of customized packages to suit your needs. The Secure Plus plan provides basic coverage for older vehicles, focusing on essential components like the engine and transmission. For more comprehensive coverage, our Supreme and Superior plans offer varying levels of protection, with the Supreme plan offering nearly bumper-to-bumper coverage.

Regardless of your plan, our warranty packages include standard perks like 24/7 roadside assistance, rental car reimbursement, and trip interruption coverage. For a small activation fee, you can also take advantage of our Elite Benefits, which include complete tire protection, up to $500 in collision coverage, and key fob replacement.

To learn more or get a FREE quote, contact our award-winning customer service team at (800) 253-8203 or shop online for an instant price.

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