CAN Multiplexing worksheet

Controlled Area Network Board

In the patterms I captured the strt and finish is where there is a long pause. The big square rectangle pattern.

The relationship between the 2 patterns and their base voltages are very similar just in the opposite direction. CAN high gets pulled down. CAN low gets pulled up.

As you can see all the paterns I captured are all different because they are all different messages. The one for the left indicator is different from the one for the right indicator. The message that its sending is different so the 0s an 1s change.

Electronic tranz & scan toolz- ON CAR

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




code 14
engine coolant temperature signal voltage low
possible cause ECT signal voltage has been above 140degrees celsius for 1 second
default action TCC apply cold

code 21
throttle position sensore signal voltage high
possible cause DTC 21 will set if TPS signal voltage has been above 4.9volts for 2 seconds while the engine is idling
default actions are:
*firm hard shifts
*set line pressure to maximum
*fixed shift points
*no 4th gear if in hot mode
no TCC operation

ABS wheel speed sensors- ON CAR

The car I worked on has a analogue wheel sensor. I concluded that the wheel sensor was analogue because it had 2 wires coming out from the sensor.

The air gap and visual condition of each wheel sensor
Front right - .35mm, visual inspection is good
Left front - .35mm, visual inspection good
Right rear - .35mm, visual inspection good
Left rear - .35mm, visual inspection good

When i connected the oscilloscope to a wheel sensor I got analogue pattern

ABS relayz

ABS demonstrators

Wiring diagram practices

Wheel speed sensors and wire colours for each sensor
Right front: Black + White -
Left front: Red + Green -
Left rear: Blue + Pink -
Right rear: Yellow + Brown -

ABS wheel sensors are braded wire to stop interference
Fuses used in ABS circuit
*Main fuse
*ABS fuse 50amps
*Gauge fuse 10amps
*Dome fuse 20amps
*Stop fuse 15amps
*ECU fuse 15amps

Earths used wire colour and pin numbers
10b
7b
white and black

ABS actuator identify which solenoids which wheel cylinder. Wire colours and pin numbers
Right front wheel - pin number 6b 5b, wire colour red,white / red,green

Left front wheel - pin number 1a 2a, wire colour blue,red / blue white

Left rear wheel - pin number 12b 11b, wire colour brown,white / brown, red
Right rear wheel - pin number 14a 15a, wire colour green,black / green, yellow

Under normal braking inlet valve open, outlet valve closed

To reduce wheel brake pressure inlet valve closed, outlet valve open

To hold brake pressure inlet valve closed, outlet valve closed

When ABS is operating to increase wheel brake pressure its constantly changing to maintain maximun brake pressure without blocking up so it does all the 3 conditions above

The ABS motor is working when applying brake pressure

ABS wiring & operation

Think about ABS repairs- OFF CAR

*Spiked by careless welding, ie MIG welding without disconnecting the battery
*Enclosure seal damaged and with obvious sign of water ingress
*Obvious signs of mechanical damage to the enclosure
are possible causes for damaging an ECU
ECU's are misdiagnosed as faulty because of inexperience faultfinding of technician. Faults are much more likely to be with connections or sensors.
Diagnostic practices to test an ABS System - voltage drops at different points of the circuit, resistance test, test for continuity in the circuit