ABS sensor resistance Lexus px 300

Methods for checking the ABS sensor

ABS sensors play an important role in the operation of the vehicle's braking system - the braking efficiency and the smooth operation of the unit as a whole depend on them. Sensor elements transmit data on the degree of rotation of the wheels to the control unit, and the control unit analyzes the incoming information, building the desired algorithm of actions. But what to do if there are doubts about the health of the devices?

Signs of device malfunction

The fact that the ABS sensor is faulty is signaled by an indicator on the instrument panel: it lights up when the system is turned off, goes out even with the slightest malfunction.

Evidence that the ABS has stopped "interfering" with the brakes:

• The wheels constantly lock up under heavy braking.
• There is no characteristic knocking with simultaneous vibration when pressing the brake pedal.
• The speedometer needle lags behind acceleration or does not move at all from its original position.
• If two (or more) sensors on the instrument panel fail, the parking brake indicator lights up and does not go out.

The ABS indicator on the dashboard indicates a system malfunction

What should I do if the ABS indicator on the dashboard of the car does not behave quite correctly? You should not immediately change the sensor, you first need to check the devices; this procedure can be performed independently, without resorting to the services of highly paid masters.

Health check methods

To determine the state of the part, we perform a series of actions to diagnose it, going from simple to complex:

1. Let's check the fuses by opening the block (inside the passenger compartment or in the engine compartment) and inspecting the corresponding elements (indicated in the repair / operation manual). If a burnt component is found, we will replace it with a new one.
2. Let's take a look and check:
   • connector integrity;
   • wiring for abrasions that increase the risk of a short circuit;
   • contamination of parts, possible external mechanical damage;
   • fixing and connecting to the ground of the sensor itself.

If the above measures do not help identify a device malfunction, it will have to be checked with devices - a tester (multimeter) or an oscilloscope.

Tester (multimeter)

For this method of diagnosing the sensor, you will need a tester (multimeter), instructions for operating and repairing the car, as well as PIN - wiring with special connectors.

The device combines the functions of an ohmmeter, ammeter and voltmeter

Tester (multimeter) - a device for measuring the parameters of electric current, combining the functions of a voltmeter, ammeter and ohmmeter. There are analog and digital models of devices.

To obtain complete information about the performance of the ABS sensor, it is necessary to measure the resistance in the device circuit:

1. Raise the vehicle with a jack or hang it on a lift.
2. Remove the wheel if it obstructs access to the device.
3. Remove the system control box cover and disconnect the connectors from the controller.
4. We connect the PIN to the multimeter and the sensor contact (the rear wheel sensor connectors are located inside the passenger compartment, under the seats).

We connect the PIN to the tester and the sensor contact

The readings of the device must correspond to the data specified in the manual for the repair and operation of a particular vehicle. If the resistance of the device:

• below the minimum threshold - the sensor is faulty;
• approaches zero - short circuit;
• unstable (jumping) at the moment of tightening the wires - a violation of the contact inside the wiring;
• endless or no readings - cable break.

Attention! The resistance of the ABS sensors on the front and rear axles is different. The operating parameters of the devices are from 1 to 1,3 kOhm in the first case and from 1,8 to 2,3 kOhm in the second.

Video "ABS sensor diagnostics"

How to check with an oscilloscope (with wiring diagram)

In addition to self-diagnosis of the sensor with a tester (multimeter), it can be checked with a more complex device - an oscilloscope.

The device examines the amplitude and time parameters of the sensor signal

An oscilloscope is a device that studies the amplitude and time parameters of a signal, which is designed to accurately diagnose pulse processes in electronic circuits. This device detects bad connectors, ground faults and wire breaks. The check is carried out by visual observation of the vibrations on the screen of the device.

To diagnose the ABS sensor with an oscilloscope, you must:

1. Fully charge the battery in order to observe the voltage drop (spikes) on the connectors or leads during the measurement.
2. Locate the touch sensor and disconnect the top connector from the part.
3. Connect the oscilloscope to a power outlet.

Connecting the device to the ABS sensor connector (1 - toothed disc-rotor; 2 - sensor)

The status of the ABS sensor is indicated by:

• the same amplitude of the signal fluctuation during the rotation of the wheels of one axle;
• the absence of amplitude beats when diagnosing with a sinusoidal signal of a lower frequency;
• maintaining a stable and uniform amplitude of signal oscillations, not exceeding 0,5 V, when the wheel rotates at a frequency of 2 rpm.

Note that the oscilloscope is a rather complex and expensive device. Modern computer technology makes it possible to replace this device with a special program downloaded from the Internet and installed on a regular laptop.

Checking a part without instruments

The easiest way to diagnose a hardware-free device is to check the solenoid valve on the induction sensor. Any metal product (screwdriver, wrench) is applied to the part in which the magnet is installed. If the sensor does not attract it, it is faulty.

Most modern automotive anti-lock braking systems have a self-diagnosis function with error output (in alphanumeric coding) on ​​the on-board computer screen. You can decipher these symbols using the Internet or the machine's instruction manual.

What to do if a breakdown is detected

What to do with the ABS sensor if a malfunction is detected? If the problem is the device itself, it will have to be replaced, but in the case of electrical wiring, you can fix the problem yourself. To restore its integrity, we use the “welding” method, carefully wrapping the joints with electrical tape.

If the ABS light comes on on the dashboard, this is a clear sign of a sensor problem. The described actions will help to identify the cause of the breakdown; however, if knowledge and experience are not enough, it is better to contact the car service masters. Otherwise, illiterate diagnostics of the condition, coupled with improper repair of the device, will reduce the effectiveness of the anti-lock braking system and may lead to an accident.