Our company uses an IQAN MDL2 setup which ties into the J1939 network of a Caterpillar system.
Our setup is using the internal resistor on the MDL as the terminating resistor on one end of the network and has a standard 120 Ohm resistor wired into the other end.
A machine in the field is having CAN network issues. Typically I am used to checking the resistance of the CAN network and the resistance of the terminating resistors as a standard checkout of the wiring. However with the internal resistor this is proving difficult.
In our lab I powered up a test MDL2 and checked resistance at the MDL with the MDL powered up but no other wiring attached. I found that I would measure ~69 Ohms across the internal resistor at first power up. If I shorted the CAN Hi and CAN Lo together by touching together my multimeter probes it would cause a CAN C "CRITICAL ERROR". After this error I would measure ~115 Ohms across the resistor until the power was cycled on the MDL.
All this said, my questions are:
-Do you have any recommendations for a standard procedure for troubleshooting CAN wiring/resistance?
-In light of the testing I did in our lab could you provide an explanation on how the internal terminating resistor on these IQANs work?
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