Driving with Bad Speed Sensors: Risks and Signs

Bad speed sensors effects signs causes, A car’s speed sensor is responsible for sending and receiving signals, which then in return sends speed and rpm information to the computer. Speed sensors malfunction in different ways. It can be that the signal it sends has a glitch or that it stops working altogether. Other times, you may experience ‘check engine lights due to issues with the signal the sensor sends. If you do run into such issues with your car, there are faster approaches for getting it fixed than changing the spare part altogether.

Now the big question is, how long can you drive your car with a bad speed sensor?

Bad speed sensors effects signs causes

Usually, a speed sensor irregularity will not cause your car to stop running, so you might still be able to drive over long distances. However, modern cars have gotten really smart, and with the integration of systems, a faulty speed wheel could bring your vehicle to a halt.

What are speed sensors?

 It’s vital to understand the role of a speed sensor before thinking about how long you can drive without one or all.

Speed sensors are attached to each wheel in a car, meaning that if your vehicle has four wheels, it also has four speed sensors. These speed sensors’ sole function is to detect the wheel’s speed and send the information in the form of electric signals to the transmission/ESP/ABS control unit system. Notably, the speed sensors on modern cars can detect the rotational speed of the wheel they are attached to.

What happens when speed sensors break?

With that in mind, here’s what happens when one of them is not working correctly:

When a speed sensor is faulty or completely broken, it could send wrong or no signals at all to the connected system. This can be the ESP, ABS, or ECM system.

When the ABS interpret these wrong signals, it could lead to anomalies like difficulty in changing gears, or some driver assistant functions like cruise control might begin to malfunction.

Therefore, while a bad speed sensor does not stop your car from running, it sends bad signals to the ABS or transmission, which in turn interferes with how some of the smart features operate.

That said, it’s dangerous and not advisable to drive a car with bad speed sensors. More so because they are fast and cheap to replace. Consequently, even when it’s just one of them that’s malfunctioning, it’s always advisable to change all of them.

Signs that your car has a bad speed sensor            

Bad speed sensors effects signs causes, Here are a few indicators that one or several of your car’s speed sensors is not functioning properly:

  1. Transmission problems

As we’ve observed, a poor speed sensor makes gear changes difficult. Automatic automobiles’ shift timing is determined by speed sensor data sent to the transmission. Thus, hard shifts, delayed shifts, and limited gear performance are common indicators of a defective speed sensor.

  1. Inability to engage cruise control

Normally, your vehicle’s cruise control will be disabled automatically by the  PCM when it fails to receive information from the VSS. This is because cruise controls require the speed data to keep your vehicle running at a constant speed.

  1. Irregular speedometer readings

Most vehicles use the VSS as the main input for speedometer readings. Consequently, any issues with the speed sensors will cause erratic or no speedometer readings at all.

Your vehicle will continue to run with or without speedometer readings. However, driving without knowing how fast you’re going is quite dangerous.

  1. Check engine light is triggered.

The PCM can trigger your check engine light for various reasons. One of these reasons is a faulty VSS. To confirm if a VSS malfunction has triggered the light, you’ll need to connect your vehicle to an OBD-II scan tool.

  1. Lack of torque converter clutch application

The torque converter clutch is activated at a pre-programmed speed. Without correct speed information from the VSS, the torque converter will not be able to apply the clutch and form a mechanical link between the transmission and the engine.

What causes speed sensors to fail?

Bad speed sensors cause symptoms, After learning what happens when speed sensors fail, let’s examine their causes:

Damage to the sensor itself

The most obvious cause for a speed sensor failure is physical damage to the speed sensor itself. It is possible for the speed sensor to get cracked. The plastic portion can also become brittle after prolonged use. Additionally, the magnetic part of the sensor is vulnerable to wear and tear after extended use.

An electrical problem in the sensor

An internal electrical issue can cause the speed sensor to send a faulty or no signal.To ascertain this, you can test the speed sensor with an oscilloscope or a voltmeter.

Poor vehicle maintenance

Not following your car maintenance schedule can cause speed sensor failure. When the magnetic pickup or toothed wheel is covered in muck, especially old transmission fluid pollutants, it cannot read accurately.

How do you know which ABS sensor has failed?

Bad speed sensors effects signs causes, Disassembling your wheel hub and examining the ABS sensor for damage isn’t a guarantee of proper operation. This may work if the sensor is physically broken, but internal faults do not show up.

As a result, you will need a troubleshooting device to run diagnostic tests and pinpoint exactly which sensors are problematic.                                                                                                                                                                                                      

How long can you drive a car with bad Transmission sensors?

Bad speed sensors effects signs causes

Don’t get confused here. Wheel sensors are also called transmission sensors for the reasons we saw above. In fact, they are also called ABS sensors and wheel speed sensors.

To wrap it up

Speed sensors are a small but vital component in any modern car. Always contact your repair shop whenever you suspect that they are not working properly.


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