ABS wheel speed sensor error. Symptoms, diagnosis, repair.

Diagnostics and repair of errors in wheel speed sensors in the car.

Wheel speed sensors are essential components of the ABS (Anti-lock Braking System) and ESP (Electronic Stability Program) systems, which ensure appropriate traction and stability of the vehicle during braking and maneuvers. Improper operation of these systems may lead to serious consequences and dangers. This article provides a comprehensive guide to diagnosing and repairing common wheel speed sensor errors.

Causes of wheel speed sensor errors

Wheel speed sensor errors may result from various reasons. Most often, this is related to damage to the sensor itself, problems with the electrical installation between the sensor and the controller, or damage to the ABS controller itself. Each of these situations requires appropriate diagnostics and the use of various solutions in the repair process.

Damaged wheel speed sensor:

Symptoms: Warnings on the dashboard (ABS/ESP light), and after connecting the diagnostic tester — errors indicating sensor failure. Sometimes absurd wheel speeds may appear in the reading, and the speedometer itself may stop showing the vehicle's speed while driving.

Diagnostics: Visual inspection of the sensor and its installation should be performed. It is best to check the sensor with a meter/ohmmeter for resistance. A good method may also be to replace the sensors on the other wheel. If the error disappears, we know that it was the sensor's fault. If the error remains, there is a problem with the cables or the controller itself, and the wheel speed sensor can be left alone.

Repair: If the sensor is physically damaged (e.g. by corrosion, mechanical damage, etc.), it must be replaced with a new one.

Damaged electrical installation between the sensor and the controller:

Symptoms: No signal or fading signal from the sensor, communication errors between the sensor and the controller.

Diagnostics: Check connectors and wires for insulation damage, connector corrosion, or broken wires. Use a multimeter to check the continuity of the cables. You should also rule out whether there is any ground leakage or short circuit between the sensor wires. Just checking the signal transition on the cables is not enough. Some people, instead of playing with a multimeter, prefer to immediately cut the cables short at the controller plug and at the sensor itself, and then lay a new cable along the shortest line of resistance, which will eliminate the problem.

Repair: Damaged cables or connectors should be repaired or replaced, ensuring that the connections are well secured and insulated.

Damaged ABS controller:

Symptoms: Continuous or recurring ABS errors, and after connecting a scan tool — errors indicating sensor failure. Sometimes, even the speedometer itself may stop showing the vehicle's speed while driving.

Diagnostics: If the sensors and the electrical installation have been checked, a problem may be suspected in the ABS controller itself.

Repair: If the ABS module is damaged, it is often necessary to replace it. However, some old controller models can be repaired. If you are in such a situation and have a BOSCH 5.7 or ATE MK20 ABS pump, please contact us. We will present you with a repair offer, but if the problem concerns another pump, the only option is to replace it with a new one.

In newer vehicles, regardless of the type of the above-mentioned faults, there may also be problems with other components in the car that use wheel speed readings in their work;ł. These are, for example, some gearbox controllers that will not allow you to use their full capabilities if they notice a problem with the wheel speed sensors.

“Have you checked the sprocket in the wheel?”

Customers often call us with yet another unusual problem. The failure described is incorrect speed reading on one of the sensors while driving and ABS operation even with light braking. And here's an interesting fact — This is not one of the faults described above. The problem most often lies in a corroded wheel crown! If this element is corroded or missing a tooth, the sensor at higher speeds will read a different speed than the others, which may result in errors related to the wheel speed sensor.

Time, money and understanding the problem

We hope that we have dispelled all doubts regarding the wheel speed sensor failure and all issues related to it. As you can see, sensor errors can have many causes, and the diagnosis itself is not simple at all. This article was created to make mechanics and customers aware of how many activities need to be performed in connection with the diagnosis and repair of a fault that, at first glance, seems very simple, but can cost a lot of time, work and sometimes more money than it might seem. It is also important not to send controllers for repair without first checking the remaining elements of the system. This sequence of actions will save our time and your money.