Controlled Area Network Board

below is picture of the board i was working on:

using the duel trace feature on the oscilloscope i captured a full pattern on the high CAN and low CAN:

the top pattern is the high CAN and the bottom pattern is the low CAN.
the base voltage is 2.5V as the high CAN goes above the base voltage, the low CAN goes the same voltage below 2.5V.

for each of the following inputs i captured a pattern for them.

right indicator:

left indicator:

stop lights:

reverse lights:

all of these patterns are different from eachother because the CAN system sends out a different signal for each individual application. the signal works by sending a serial number made up of zeros and ones, this can be read to make a signal if you know how to analyze it.

in the below wiring diagram i was asked to identify the input and output pins, wire colours and relay transistor for the rear wiper and the indicator:

CAN - Multiplexing Worksheet

for this task i used a 2005 range rover.

the twisted wire pair were located next to the ABS modulator. one wire was coloured yellow and brown, the other wire was coloured yellow and black.

i then recorded a waveform from one of the wires below.

the wire colour i used was yellow and brown.
i used a 5 micro second time frame
volts per division 1V


i then recorded a waveform of the other wire:

this was the yellow and black wire
time per division = 5 micro seconds
volts per division = 1V

aliasing is described as:
jaggerd, stairste effect on curved or diagonal lines that are produced in low resolution, as in a computer printout or display.

these waveforms are not aliasing because they are not as described above.


the first waveform, the main voltage on the line is 2.5V
the other voltage on the line, when the voltage is pulled down is 1.4V
in the second waveform the main voltage on the line is 2.5V
the other voltage on the line, when the voltage is pulled up is 3.5V


SCAN TOOL OBSERVATIONS

on the scan tool, the different functions to examine the CAN system are:

control unit versions
fault codes
actual valves (all select)
actual valves (manual select)
actuations

these are the systems that are controlled by the CAN system:

lights - low speed
wipers - low speed
washer fluid - low speed
central locking - low speed
airbag - high speed
window actuators - low speed
instrument cluster - high speed
ABS - high speed
mirror - low speed
air conditioning - low speed

On Vehicle Testing

ABS WHEEL SPEED SENSORS

on the vehicle i was assigned to use, there was analogue wheel speed sensors, i found this out by checking how many wires it had, my sensors had two wires.

i could not measure the air gap of my sensors because the was a metal plate in the way and i did not have the time or resources to take it off.
i did however, do a visual inspection and the teeth on the gear looked intact and the sensor looked in good condition.

below is a wheel speed sensor that looks similar to the one that was on my vehicle:

http://www.instructables.com/id/Magnetic-speed-sensor/

i then recorded a waveform with an oscilloscope, this shows how the voltage goes up and down as the teeth on the gear pass by the magnetic pick up:

USING A SCAN TOOL

for this exercise i used a 1997 Mitsubishi Galant, this had OBD2.
i then hooked up the scan tool and brought up the live data screen for the ABS, the results are below:

Front right wheel speed sensor
rear left wheel speed sensor
front left wheel speed sensor
rear right wheel speed sensor
brake light switch

i then went to the actuation screen and activated a few inlet and outlet solenoids to make sure they were working.


ELECTRONIC TRANSMISSIONS AND SCAN TOOLS

PCM = powertrain control module
TCC = tourque converter clutch
TPS = throttle position sensor
ECT = engine coolant temp sensor
VSS = vehicle speed sensor
PSA = transmission range fluid pressure switch assembly
TTS = transmission temp sensor



sensors and actuators:

wiring diagram for the above inputs and outputs:

Antilock Braking Systems Lab Workbook

firstly i was asked to find out about what could damage an ecu.

if you dont disconnect the battery when welding you can get a spike which could damage the ecu.
if the enclosure seal is damaged the ecu could get water damage.
damaging the ecu could wreck the inside components.
most common faults are just loose connections or faulty sensors.


the next task i had to label the components of the braking system:

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



i was then asked to find the wheel speed sensors on the wiring diagrams below and list the wire colours of each sensor:

right front =  - white/ + black
front left =  - pink/ + blue
rear left =  - green/ + red
rear right =  - brown/ + yellow

the ABS wheel speed sensor has braded wire to stop frequency.

the fuses that are used by the ABS circuit are:
ABS fuse box, fusable link main, gauge, dome, stop, ecu

using the wiring diagram i was asked to find the earths for the ABS control unit and the ABS motor and their wire colours:

pin 10/ block B = W-B
pin 7/ block B = W-B


i was then asked to identify the solenoids to control each wheel cylinder and note the wire colours and pin numbers.

front right wheel = 2B/ 6B     red-white/ red-green
front left wheel = 3B/ 7B     blue-red/ blue-white
rear left wheel = 1B/ 5B     brown-white/ brown-red
rear right wheel = 4B/ 8B     green-black/ green-yellow


using the diagram below i was asked to say if the inlet and outlet solenoids were open or closed:

under normal braking:
inlet valve open and outlet valve closed

ABS operating to reduce wheel brake pressure:
inlet valve closed and outlet valve open

ABS is operating to hold brake pressure:
inlet valve closed and outlet valve closed

ABS is operating to increase wheel brake pressure:
inlet valve open and outlet valve closed

the motor pumps fluid in and in some cases the pump sucks fluid out aswell



below is a digital signal of a wheel speed sensor that switches 5 volts every 2 seconds:

http://ttec4825rex.blogspot.com/2010_10_01_archive.html

below is a analogue signal with a frequency of 0.5Hz and a maximum of +3 volts:

http://ttec4825rex.blogspot.com/2010_10_01_archive.html

ABS DEMONSTRATORS

on the wiring diagram below, i was asked to find the ABS sensor pin out connections to the ecu and record the which ecu wires go to which wheel speed sensors:

left front = ecu pin #4 and 5
left rear =  ecu pin #7 and 9
right front = ecu pin #11 and 21
right rear = ecu pin#24 and 26

this was a magnetic inductive type of speed sensor.
this has a magnetic pick up sensor with a cog that spins around. Each time a tooth passes by the sensor it creates a voltage, this charges up the windings on the sensor side.

below is a some waveforms of the the wheel speed sensors, i used a "tektronic TDS 1001B" oscilloscope.


right front:

left front:

right rear:

left rear:

i then measured the AC voltage with the wheel speed sensor spinning:

left front = 3.59V
left rear = 3.21V
right front = 3.00V
right rear = 3.62V

a multimeter cant give as good as a reading as an oscilloscope can because a oscilloscope gives an actual waveform and you can see what the voltage is doing.


ABS RELAYS

ABS ECU relay = K39
ABS pump relay = K100
ABS HCU solenoids = Y22 (hydrolic modulator)

power to ABS ECU = 26 A
control wire for ABS ECU = 1 B
power to ABS pump = 8 E
Control wire for ABS pump = 2 H


below is a relay waveform that shows both the control circuit change when it turns the relay and the power switching on to power something in the ABS system:

http://amirs4825.blogspot.com/2010/11/abs-relays.html

the bottom waveform is the control circuit and the top is the switching circuit.
the point between A and B is when the switch is on and running 12V.
C is when the control circuit is collapsing.
D is when the switch is about to turn on again and E is a slight oscillation.

below is a waveform  that shows the control circuit change when it turns on the relay and thepower switching on to power the ABS pump.

the top waveform is the switch, this is earth triggered and shows that when the key is on, the waveform drops strait down and when the key is turned back off, the waveform goes back up to its original state.
the bottom waveform is the pump, when the key is earth triggered, the pump starts to work, then when the switch is off, the pump winds down and goes back to its original state.

when the key is turned on, the ABS system begins to self test, this checks all of the components of the system except for the wheel speed sensor that can not be checked unless the vehicle is moving. this is because the wheels need to be moving to send a signal output.

i created a fault in my system by slowing down the wheel, this makes the system think that i am braking fast and am going to lock up the wheels, brake pedal then started pushing back up against my hand and the inlet solenoid for that wheel closed and the outlet valve opened to relieve pressure from the brakes.

Honda Multiplexing Board

on this system i was asked to identify the plugs, pins and wire colours of the communication wires between the nodes.

door: block A/pin 15 to drivers: block A/pin 2 = brown wire
drivers: block B/pin 1 to passengers: block B/ pin 9 = pink wire


i was then asked to identify the plugs, pins and wire colours of the  earths and voltage supply lines between the nodes.

door earth: block A/pin 12 and block A/ pin 19 = black wire
drivers earth: block A/ pin 14 and block B pin 4 = black wire
passengers earth: block B/pin 22 and block A/ pin 8 = black wire

door supply:  block A/ pin 1 = pink wire
drivers supply: block A/ pin 1 = wht/blk wire -  block A/ pin 12 = pink wire
passengers supply: block A/ pin 22 = yellow wire

i then asked my tutor to create a fault in the unit

i found that none of the windows would work except for the drivers window. the door locks were also not working but the interior lights were working fine.

i then looked at the wiring diagram and found that the communication wires could be damaged or cut and not allowing a signal to be sent.

once i did that, i then put the system into "test mode 1".
the test mode made one short beep, this meant that there was a fault where i expected according to the data sheet.

i can not check the resistance between these wires because you can not put amps into this circuit.

i then did a voltage drop test and found that there was a 200mv drop between the door and the drivers node. this indicates that there is an open circuit between the two nodes.
between the passengers and drivers node there was 0V drop which shows the communication wires between theses two nodes are in tacked.


i then put the system in to "diagnostic mode 2" and came to the same conclusion that the communication wire between these two nodes are damaged or cut. none of the electronics work except for the drivers window which does not go through the other nodes to actuate.


by looking at the wiring diagram. to make sure that this wire is defiantly cut i would unplug the blocks between the drivers node and the door node, i would then test for continuity between the the drown wire at block A/ pin 15 and block A/ pin 2