Scotty, I have a 1999 Mercedes Benz C280 with obd 1 and obd 2 ports and having can bus issues. I have a Vident iLink 400 and it has limited capability's even with current soft ware. I have tried to use a multi meter to test can hi can lo and I get the proper voltage but when it comes to resistance I get 31ohms. I believe 120 ohms is proper. I have rebuilt the valve body with up grades, conductor plate new, solenoids tested and are spot on with factory ohms, checked tcm, ecm and they are detected with iLink 400. Is there a proper scan tool that will pin point the issue and tell me what the issue is down to the letter besides giving a general code?
There's a 120 ohm termination resistor on each end of the CAN Bus.
So if you measure resistance between the CAN HI and CAN LO wires, you should measure around 60 Ohms over these 2 wires (because there are two 120 Ohms resistors in parallel).
Sometimes there are additional resistors on the CAN Bus. Sometimes they're in devices on the CAN Bus.
So, if there are 3 resistors in the wiring, you'll measure 40 Ohms, and with 4 resistors you'll measure 30 Ohms.
The thing is, if you had a short to ground issue on 1 of the CAN Bus wires, you would have spotted an anomaly in the voltages when you measured them. You didn't.
Also, even back in 1999, I think Mercedes was using a CAN-C (high-speed) bus for the powertrain, transmission and ABS modules, and a slower CAN-B bus for the body control stuff. That CAN-B Bus can have dozens of modules on it.
You didn't mention which, if any, "U" codes your Mercedes was throwing to point you in a direction.
So, in your shoes I'd invest the money in a good scanner. No scanner is going to point you to the exact problem and fix, but it will give you a great direction to start. Look up "Mercedes U codes" and you'll get an idea of where the "U" prefix DTCs (Diagnostic Trouble Codes) can point you.
Also, "spring" for a 1 year subscription to a manufacturers' diagnostic and repair information site like ALLDATA DIY ($30) You'll have access to the wiring, modules, and the connectors and their locations of your CAN Bus circuits.
(This isn't one of them, just a general diagram showing the 120 ohm termination resistors)
what are your symptoms please?
