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