CAN Bus communication error code on code reader

Hi and thank you for visiting us here at 2carPros.

So i see that you measured the resistance between the CAN-H and CAN-L. 60 Ohms is where you should be so that means you are terminated correctly. The problem I see here is that if you are reading 0.2 volts, that indicates to me that you most likely that you have a short to ground. Possibly an intermittent short to ground. With the system off, can you measure the resistance between CAN-H to ground? And then CAN-L to ground? Both of these should be 1 Megaohm or higher.

Let me know what you find.

Jon

Hi, it was in megaohm both side, but as I wrote it is CAN D,
So I re write my finding:
CAN C all normal finding and has signal on oscilloscope .
CAN D, only resistance between H and L is normal , no signal on oscilloscope, Both H &L show Megaohm resistance to ground and or positive battery side.
And for long time H & L ( only on CAN D) have been having fixed 2.5 volt it seems CAN D is dormant, But l now they have changed to very low equal voltage.
Because I need the car I still using the car in limp situation.
Sincerely appreciate.

Hi,

I noticed it has been a few days since we made contact with you. Have you made any progress? We're interested in knowing.

Take care,

Joe

Hi, Actually no, I believe my car need new gateway module ,CGW,but I don’t know how I am able to buy a new CGW and how reprogram it.
Sincerely appreciate.

Hi,

That is a tough one. It will have to come from a dealership. If I remember, once they are programmed, they can't be changed. So, a used one will likely not work.

As far as programming, you need software from Mercedes, which means a dealership again.

Listen, I have a good friend that has a Mercedes repair shop. I'm going to discuss this with him and see if he has any suggestions. Hopefully, he will have a suggestion. I won't be able to see him until tomorrow.

Joe

Hi , thanks for your generous support, last year. I have similar problem with my transmission control module, but fortunately I could find a guy in Toronto who provided me a new TCM and programmed it for me. it cost me one third of dealership cost .
Other side of problem is that I am not sure about it, may my CGW is good.
Sincerely appreciate .
Fariborz

Hi,

I didn't forget. I ran down earlier to discuss it, He suspects it is somehow tied into the gateway module as well. I copied your posts so I could discuss them with him and he said because of the complexity of the system, he wouldn't want to just guess. He was even pointing out the ignition switch module can be causing the issue. Ugh!!! I love technology.

I wish I had a better answer for you. I don't know if you want to, but it may be a good idea to remove the module and have it checked by a dealer. You need someone with the correct software for testing.

Joe

Hi,

Thanks, everything is possible, at first I think about it, then when I found no communication error codes and abnormal findings in CAN D my approach has changed, but unfortunately I don’t have wiring diagram and dealer service is very expensive. I continue to use the car in limp mode Fortunately I should drive only on low speed road. Even finding locations of different parts of the systems is difficult. I found them in front of passenger foot that need remove all of the floor covering and with a thick isolation material. My next step is checking connections in CGW, easy to say.
Be safe,
Fariborz

Hi,

Do me a favor. Let me know what specific schematics you need. Mercedes is very protective of their technical information, so it isn't something I can get from my manuals. However, I will try to find it for you.

Let me know.

Joe

Hi, thank you for your generous support, you are 100% correct , I bought a hacked Mercedes manual but it is useless, though I think the best thing is actually a simple schematic wiring diagram of CAN bus, it simply show position and communication different module on network .
Sincerely appreciate
Fariborz

Hi,

I just spent about 40 minutes trying to find a schematic of the CAN. It breaks it down by component. Then when I go to a specific component, there is no schematic. Interestingly, it indicates to see the factory manual.

I honestly tried. I'm going to ask the site owner if he has any recommendations.

Take care,

Joe

Sincerely appreciate.

Not a problem. I hope things work out for you.

Take care,

Joe