CAN wiring

for motec m150 i use can3 for ecu/dash and can2 for ecu/LTC. so, i need in total 4 terminate resistor 120 ohm (two for each bus) right, but i when i check for lambda it doesn't show any value. so, i remove one resistor on my can2 and it works.can anyone explain to me how this happened.

Not enough detail to know where your mistake was. Good job finding it. Did you check the resistance on the bus?

yes, i check resistance for can2 that i use for my LTC before I installed my LTC.It shows 60 ohm which is not the problem right? (120//120=60 ohm) but it doesn't work. Here is my diagram for what i did.

It should have worked correctly with the upper diagram, perhaps you swapped CAN Hi/Lo (it happens pretty often to all of us). I'm not sure how you detected the lambda wasn't working -- the M150 normally disables it until the engine cranks. And then it usually takes about 30-60 seconds before you see a value appear.

You might want to use other ways to check the CAN bus is working. Did you look for messages on the CAN bus using CAN Inspector? Or just didn't see an "Exhaust Lambda" value?

i didn’t use can in-spector maybe the wiring was wrong at first but I’m curious,how does second diagram work with only one 120 ohm resistor.

Most CAN buses (particularly simple point-to-point) work just fine with single resistor. Yes it's not quite within spec, but we don't see any issues.

thank you so much David.