The speedometer is the instrument to consult when you want to know the instantaneous speed readings. Road safety depends on many factors, and maintaining a good speed limit is one of them. So, when the speedometer is not working, you don’t know if you’re driving too slowly or too fast.
This could be dangerous on a road where driving at a low speed is essential for safe driving. Additionally, you could be stopped by a police officer for exceeding the maximum speed limit.
Know the symptoms and reasons for a faulty speedometer. Furthermore, some suggestions and tips would be helpful in deciding how to fix it.
Symptoms of a Speedometer That Is Not Working
The speedometer determines the vehicle’s speed by extracting information from the transmission and the driveshaft.
The ECU (Engine Control Unit) converts the rotational speed of the driveshaft into the vehicle’s linear speed, then transmits the information to the speedometer.
When the car’s speedometer is not working, it cannot translate the information from the ECU. A faulty speedometer is a potential safety threat.
The warning signs to look for are:
The speedometer is completely dead! A problem with the speed sensors or the speedometer head is the reason. Worn connecting cables are the culprits in older cars.
Check that the engine light comes on. This happens due to a faulty sensor that cannot process the information received from the ECU. This also causes erratic behavior of the speedometer.
Frequent changes in the readings. The problem also occurs due to bad wiring or faulty sensors. Recalibrating the sensors or repairing the wires will resolve the issue.
Changing to tires larger than the manufacturer’s recommended dimensions can also be a cause in this case.
The speedometer displays incorrect values because it is calibrated according to the dimensions of the factory-installed tires.
What Causes the Speedometer to Stop Working?
Speedometers in modern vehicles use speed sensors to calculate speed, while older models use gears and cables for the same purpose. It stops working when the sensors malfunction, the dials malfunction, or the wiring becomes faulty.
Examine these components when the speedometer is not working.
Faulty Speed Sensor
A speed sensor not only indicates the vehicle’s speed but also contributes to the operation of the cruise control and the regulation of fuel flow and ignition timing.
A speedometer may stop working due to a faulty sensor. Furthermore, the affected cruise control can disrupt the car’s driving functions. Any problem with the sensor will turn on the Check Engine light.
Problems with the ECU
The Engine Control Unit (ECU) is literally the hub of the engine’s activities, acting as the car’s computer brain.
It monitors and controls several engine activities, including speed. It is evident that the speedometer can give incorrect readings in case of certain ECU problems.
Faulty Wiring and/or Fuse
Another reason why the car’s speedometer is not working is a faulty wire. Wires can short circuit for many reasons, causing the fuse to blow and stopping the speedometer from functioning. This mainly happens on older cars.
Check Error Codes
If your check engine light is on, your mechanic can start the diagnosis by using a code reader to see what error codes appear or if other associated warning lights, such as the ABS light, come on.
Checking these codes can allow the mechanic to better understand the components causing the speedometer failure.
Your technician can also use a bidirectional scan tool to look for probable reasons in the instrument cluster (gauge cluster).
My Speedometer Stopped Working: How to Fix It?
Depending on the type, there is only one repair solution for a broken speedometer, by replacing either the speed sensor or the wiring.
With good knowledge of a motor vehicle’s mechanism, you can perform the repair work in your garage. Otherwise, calling a professional is the most logical thing to do.
Using a code scanner to examine the error codes is the first step to getting to the root of the problem.
Connecting the scanner to the ECU will help identify the failing components. It is necessary to clear the error code to complete the repair process.
1. When the Sensors are Failing
Find the location of the sensors and check them as well as the wires connecting to them for any visible damage. Replace the old one with the new unit in case you find a fault.
2. When the Wiring is Bad
Wires can short circuit or wear out in an older car and blow the fuse. Examine the wiring and the fuse and replace the faulty ones.
3. If the ECU is the Culprit Here
Then the entire ECU needs to be replaced. You can reset it, but that will only be a temporary solution. Remember to turn the ignition key to the “Auxiliary” position after installing the new unit.
This will help the ECU start the operation and begin adapting to the other engine systems when the car is turned on.
In all cases, remember to test the car to ensure the speedometer is working correctly. These are the repair processes you need to resort to in case your speedometer is not working.
Car Speedometer FAQ
- How much does it cost to repair a speedometer?
The price of speedometer repair will vary depending on the source of the problem. Replacing a speed sensor will normally cost between $100 and $200.
Replacing a speedometer cable will typically cost between $50 and $100. Furthermore, replacing the speedometer gear will normally cost between $50 and $100.
- Why is my odometer working but my speedometer is not?
If your speedometer is not working but your odometer is, look for a faulty speed sensor, broken speedometer gears, damaged cable/wiring, and a faulty engine control unit.
If your speedometer and your odometer are not working, it could be due to a faulty engine control unit, a blown fuse, or a faulty speed sensor.
Analog odometers may not work properly due to a damaged gear or another component.
On the other hand, in the case where the odometer is not working correctly but your speedometer still works, it most likely means the odometer gears are broken and need to be replaced.
- Can you drive with a speedometer that is not working?
Yes, technically. However, it is not suggested since you won’t know how fast you are driving with a damaged speedometer, whether mechanical or electronic.
Not only is it risky, but you can be severely penalized for speeding and driving with a broken speedometer.
- Can I use my phone as a replacement speedometer?
Since most phones today have GPS capabilities, they can monitor your position and determine your traveling speed. There are also speedometer and odometer apps that can help you track your car’s speed and distance traveled.
However, it may not be as accurate as your functional speedometer, and you could soon be penalized for exceeding the vehicle’s speed limit.
In several countries, using a phone as a speedometer is also prohibited. Check your local rules before driving without a speedometer.
Watch this video from Oz Mechanics for more details on how to fix a speedometer that is not working!
Conclusion
The speedometer is an integral part of the vehicle and is essential for the safety of the driver and passengers.
Therefore, it is essential to inspect and calibrate it from time to time, not until your speedometer is not working, as part of normal maintenance. Particular vigilance can help you avoid traffic jams caused by a broken speedometer.