[Real Case] Fault phenomenon description: A car with ABS anti-lock braking system, ABS system has been working normally. However, when the vehicle was driven nearly 10,000 kilometers, the vehicle did not have any abnormal situation, but the ABS warning light was always on and off.
There are many reasons why the ABS light is always on. You can first check which vehicle is yours?
1. The battery voltage is too low or the fuse is blown;
2. ABS system Wire breakage, loose plug or loose relay connection;
3, poor wheel speed sensor;
4, poor hydraulic adjustment device;
5, electronic control device bad. The hydraulic adjustment device and the electronic control unit are the core components of the ABS system. Such components are generally relatively precise and will not be easily damaged.
As a car that has traveled 10,000 kilometers, it generally does not malfunction, or it must start with a routine inspection.
1. First check if the battery voltage is 12V;
2. Check if the ABS fuse is normal;
3. Check the ABS system wire for disconnection; Br>
4, check each plug connector, whether the connection is firm;
5, check the relay, whether it is fixed firmly;
6, check the wheel speed sensor is normal.
Remove the vehicle speed sensor from the four wheels and check that the sensor head is dirty. If there is dirt, wipe the sensor head dirt and reassemble it to see if the ABS warning light is normal. The wheel speed sensor consists of an electromagnetic induction sensor head and a magnetic ring gear. The ring gear is mounted on the hub and rotates together with the wheel. When the ring gear rotates, the crest and the backlash alternately face the sensor head. When the top of the tooth is opposite to the sensor head, the gap between the two is the smallest, and the magnetic field around the induction coil of the sensor is the strongest; when the backlash is opposite to the sensor, the gap between the two is the largest, and the magnetic field around the induction coil is the weakest. The alternating flux changes, the induction coil generates an alternating voltage, and the frequency of this voltage changes in direct proportion to the vehicle speed. The vehicle speed sensor can transmit the vehicle speed signal to the electronic control device in time to control the braking force of each wheel.
If the electromagnetic induction sensor head has iron scraps, the gap between the sensor head and the ring gear will change, so that the flux change is not obvious, and the alternating voltage generated by the induction coil is irregular. The electronic control device can not effectively control the braking force of each vehicle, so that the ABS light is always on. On vehicles with an ABS system, the wheel speed sensor head easily absorbs dirt such as iron filings. When the ABS light is on, check the system first.
[Deep analysis] ABS lights are always on the following three conditions:
First, turn on the ignition switch, ABS fault light is always on. Under normal circumstances, the following three conditions will cause such a fault in the ABS system: 1. When the vehicle speed exceeds 10km/h, no speed signal is transmitted to the ABS control unit. 2. When the vehicle speed is greater than 40km/h, the speed signal exceeds the tolerance value. 3. The sensor has an identifiable open circuit or a short circuit to the positive pole and ground. If you encounter the above situation, you should focus on the following items: 1. The line connection between the wheel speed sensor and the ABS control unit. 2. The installation clearance of the wheel speed sensor and the ring gear, the installation position and the contamination by dust or impurities. 3. Is the wheel bearing clearance too large? 4. The sensor itself is faulty. Tip: When cleaning the vehicle, the engine compartment is often flushed with high-pressure water. High-pressure water will splash into the connection point of the ABS control unit, which will cause an instantaneous short circuit. This is a soft fault. The probability of a fault is very random. It is not easy to measure with a multimeter. Only when the fault occurs, the cause of the fault can be found, the root of the disease is found, the right medicine is prescribed, and the fault is eliminated.
Second, the ABS fault light is on in the train. Generally, this situation will be caused by other faults, and it will be all four locks when the brakes are suddenly braked, which means that the ABS system does not work at all.