Why does the speedometer show a higher speed? According to information published on various related car repair sites, the average speedometer on today’s modern cars tends to read a little high.
Yet, there are still other common reasons why the speedometer reading is higher than the actual speed, including the following:
- The tires are the wrong size
- Faulty sensors
- Computer error – ECU (Engine Control Unit)
To get to the root of this particular issue, you may want to start by considering each factor individually. So, let’s get started.
Contents
Tires are the Wrong Size
You may or may not know that the speedometer in your car is directly and indirectly affected by other outside factors. One of the most important is the size of the tires on your vehicle.
For example, the diameter of your tires determines the number of rotations and the speed for each mile.
As a result, for each tire rotation, the car will travel further, and the speed on the speedometer is higher.
Faulty sensors
The VSS or vehicle speed sensor can be described as a small component that has been mounted on the car’s transmission. This sensor is designed to let the vehicle’s onboard computer know exactly how fast the car is moving.
Consequently, if this sensor goes bad, the speed on the speedometer may be much higher than the car is moving.
Computer error – ECU (Engine Control Unit)
The ECU (Engine Control Unit) is often referred to as the hub for various engine activities. The ECU acts as the car’s computer brain, and is responsible for monitoring and controlling numerous engine activities, including the speedometer.
This means that if something does go wrong with the ECU, it may give a higher speedometer reading.
Can it really represent a problem if the speedometer shows the wrong speed?
Yes, the wrong speed on the speedometer can cause major problems for any driver. Here are just a few that should be noted as unsafe and problematic.
- Higher potential for causing an accident since the driver cannot match the speeds posted on the city streets or the highway accurately.
- Officer gives the driver a speeding ticket that could have been avoided
- The person may drive slower than other drivers on the road (speeds posted for school zones, highway traffic, etc.).
- Speed cannot be adjusted quickly on the city streets, highways, or in bad weather conditions
- Must show up at court to fight speeding tickets with information that must meet the court’s requirements (i.e. Supporting documentation that says the speedometer in the vehicle was not calibrated properly, etc.).
To avoid these and other related situations, the driver should make sure that the speedometer is fixed as soon as possible.
How do I fix my speedometer’s wrong speed?
To fix a speedometer’s wrong speed, the mechanic may need to troubleshoot the problem before making the appropriate repairs. For example, if the source of the problem is due to a faulty sensor or a computer error, here are some solutions.
A Faulty Sensor
To repair a faulty sensor, the sensor will most likely need to be replaced. Some auto shops may charge between $100 to $250 for the parts and labor.
Computer Error or ECU problems
ECU (Engine Control Unit) problems can vary in how they are handled. In some cases, the ECU can be reprogrammed to correct the speedometer errors. Or, an auto repair technician, in most cases, may be able to repair the ECU to fix the issue.
Also, depending on the make and model of the vehicle, the auto shop may charge between $300 and $750.
Recalibration
Once the appropriate repairs have been made, the auto shop technician or the car owner will need to recalibrate the speedometer.
If it is an electronic speedometer, here are the steps that should be followed.
- Step 1: Locate the calibration button (which can be found next to the speedometer).
- Step 2: Press and hold the calibration button
- Step 3: Start your vehicle
- Step 4: Press and hold the calibration button again
- Step 5: Test drive the car by driving your vehicle
- Step 6: Press the calibration button once more so that the speedometer will automatically recalibrate itself to the correct speed.
Conclusion
Though the answer to this question can vary from one vehicle to another, it is important to note that the average speedometer on today’s modern cars tends to read a little high.
Yet, there are other common reasons why the speed on the speedometer may not be accurate. In some cases, the cause may be due to a faulty sensor or a computer error.
Whatever the situation, an auto mechanic may need to troubleshoot each to determine the cause and the fix. Also, once the fix has been made, the speedometer on the vehicle will need to be recalibrated to the correct speed.
