antilock bracking systems

First we looked at some posible causes of damaging  an ecu,these are some of the causes:
Spiked by careless welding like mig welding without disconnecting the battery.
Enclosure seal damaged and with obvious sign of water ingress.
Obvious signs of mechanical damage to the enclosure.

When a inexperienced technician tries to fault find an ecu it might be misdiagnosed.Faults in ecu is more likely to be with connection or sensors.If these issues would occur with the ecu it might cause the abs to not work because there is a lack of comunication in the system

First task was to identify the components in the system

1=brake disc
2=speed sensor
3=tooth wheel
4=modulator
5=master cylinder
6=caliper
7=brake booster

Next I used the wiring diagram above to get some information about the abs.First I found the sensors on the diagram and list their colours:
Front right: -white  +black
Front left:  -green   +red
Rear left:   -pink     +blue
Rear right  -brown  +yellow


ABS wheel sensors has braded wire,the reason for this is to sheild other wires from frequency and for interferance.
there is a list of fuses in the abs circuit:
warning light fuse
stop light fuse
battery fuse
ignition fuse
abs fuse
battery main fuse

using the wiring diagram again i was told to identify the earths for abs wire colours and pin numbers
pin-10 white black
pin-7 white black

I was told to identify the solenoids control wich wheel cylinder:
Front right wheel
pin number:2B and 6B
wire colour:red white and red green

Front left wheel:
pin number:3B and 7B
wire colour:blue red and blue white

rear left wheel:
pin number:1B and 5B
wire colour:Brown red and brown white

rear right wheel:
pin number:4B and 8B
wire colour:Green black and green yellow

 Next task I had to do was use the picture above to give the conditions of the inlet and outlet valve solenoid valves:
abs operating to hold brake pressure
inlet valve closed outlet valve closed.

ABS is operating to increase wheel brake presure:
inlet valve open outlet valve closed.

under normal braking:
inlet valve open outlet valve closed

abs is operating to reduce brake pressure:
inlet valve closed outlet valve open.

The abs motor wil start to work when the car is locking up.It knows when this is goin to happen with the use of wheel speed sensors at each wheel.

I had to draw a digital signal that switches 5volts every two seconds.

As shown in this graph we can see after 2 seconds voltage goes up to 5v this is when it switches.It stays 5v for 2seconds then comes back down to 0 this is when it switches again.

I also had to draw a analogue signal with a frequency of 0.5Hz and a maximum of +3 volts

I got this picture of http://ttec4825rex.blogspot.com/2010_10_01_archive.html As we can see in this graph only goes up to +3 volts shown on left and comes down to -3 volts