TTEC 4825 Waveforms

This is an analogue waveform with a frequency of 0.5HZ and a maximuim of +3V.


Wheel Speed sensor waveforms.

The waveforms were similiar on all wheels the only difference being that both the left wheels were 1V and the right wheels were 1.5V.

The AC voltage across each wheel speed sensor was:

Left Front 3.5V (AC) Resistance=1.4K ohms

Left Rear 2.5V (AC) Resistance=1.43K ohms

Right Rear 5.2V (AC) Resistance=1.6K ohms

Right Front 4.4V (AC) Resistance=1.62K ohms.

Advantages of an oscilliscope over a multimeter.

An oscilliscop can identify a noisy signal or a problem like a chipped tooth rotor because there will be a huge drop off point in the signal which a voltmeter couldnt identify. The oscilliscope is a more accurate tool for diagnosing ABS wheel speed sensor. if the signal was noisy the sensor could be faulty or maybe have iron shards stuck to the magnet. This couldnt be identified by the multimeter.

Show a digital signal switching 5V every 2 seconds

ABS relay waveform (1) Power something in the ABS system.

This is showing the relay switching the ABS motor on. Changing from the control to the switching circuit inside the relay.

ABS waveform switching the ABS pump on.

This is showing the relay switcing the pump on. The voltage change between the control and switching circuit.

Fault Check:

When the key is turned to ignition the ABS system does a fault check. If any faults are detected the ABS warning lamp will stay on constantly and ABS won't work. The ABS warning lamp should stay on for 6 seconds during the self test and then turn off. In some cars it will only turn off after 8km/h. During the self test the ABS pump turns off and on. There was power at the motor wires for one second at the relay to turn the motor on.

Create a fault and observing.

I created a fault in the ABS system by slowing down the front left wheel speed sensor. The ABS warning lamp was constantly on. The ABS pump turned on as soon as the wheel speed sensor was slowed down this is because the ABS would think that wheel is locking/ skidding so it released the pressure at that wheel. The pressure gauge read almost 0psi on the front left wheel when slowed.This is how ABS functions.

ABS solenoid actuated waveform

Used pin 1.

This is showing the solenoid switching on and then off to release brake presssure