ABS SENSOR TEST

The ABS No obvious magnetic sensors checkAfter Halloween , it is the anti-lock brake problems haunt our garages. Why ? As the sensors are the key elements of the system, they are also the most likely to default . The snow mixed with salt gives a saltwater solution that puts to the test the speed sensor wheel, particularly inductive (magnetic) sensor .Text size bigger text smaller text2008-11-01

Merely enter the vehicle heat will melt the snow on the suspension components . The mixed salt water to seep into the smallest cracks sensors to betray management system . When the vehicle is delivered to the customer , the ABS warning light could suddenly turn .
And now back to the studio, not happy at all !
The management system is the first verification of these sensors when the ignition is switched to "on" ( key ON) . The management system then checks if the sensors have a voltage leakage to ground. This is made possible by a low voltage (about 2.5 volts to 5 volts) sent by the brake module and which is present at each sensor . If a sensor has a leakage to ground, the voltage will fall slightly and will be interpreted by the module as a non-functioning sensor .
Strangely , the technician , if a controller analyzer is used to make a diagnosis , the speed of the four wheel speed sensors is normal (Fig. 1 ) .
The speed is uniform over the four sensors and the deceleration thereof is at the same time . If this is the case , check whether a sensor is grounded ( see table) .
The resistance of a sensor is to be taken when a code disorders us there . It is rare ( but still possible) to detect a problem with this type of verification ( Figure 2).
The reference voltage should be checked before replacing a sensor. It is too easy to blame a sensor without first checking what is conveyed by the thread. In some cases, the wire core is attacked ( Figure 3). Instead of copper color , the wire core is black and dull.
If you encounter this case , you must change the thread in full. If you try to replace only a section, you will find it difficult to solder the wire and again, the resistance created mislead management system brakes.
If you are very attentive at given by the wheel speed sensor signal , it is possible to note that a speed sensor becomes zero km / h before the other (FIG. 4 ) Normally , it is to be demagnetized , or restraint was warped .

In the latter case , if a sensor is more distant than the other , it affects the amplitude of the signal . The management module may issue a code of disorders, but in most cases , the customer will complain that the ABS brakes are activated at the end of normal braking without wheel lock .
Why is it important to do all these checks ? 'll See a short summary of a Ford service bulletin : 04 - 26-7 (source: Shopkey5 ) for a Crown Victoria, Grand Marquis, 2002-04, "char police " par excellence.
Some vehicles may have more dia