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  #1  
Old 01-25-2006, 07:11 PM
B52 B52 is offline
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Unhappy Transmission Troubles on 98 ML 320

My transmission is slipping when shifting from 3rd to 4th gear. I went to the local MBZ transmission Guru and he hooked up his analyzer and said there was a code that says there is no communication from the CAN (car area network) to the Transmission control module. He said the module might be defective, or the problem may be in the transmission. But he suggested replacing the module first.
I really hesitate to spend $950 on a transmission control module only to learn that the transmission is the real problem. Is there any way to test the transmission control module?

PS: Great forum

B52

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  #2  
Old 01-25-2006, 07:46 PM
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Your data or interpretation of it is wrong. A 98 ML communicates with all modules except the transfer case on hardwire. The individual modules communicate with each other over CAN (controller area network).

So the CAN codes you are getting either refer to CAN or other controller codes or the controller isn't talking. If the trans controller isn't talking it would need various testing to see if it were defective. If its not talking it couldn't tell you it had CAN codes.

The question that needs to be answered is: whcih controller was talking when it said there was lack of CAN communications AND who did that controller say it couldn't talk to.

Stated differently, the CAN is not necessary for the scanner to talk to the various controllers. The trans controller needs engine data which it gets over the CAN. So if one can talk to the trans controller and it states it has CAN codes, I see no reason to blame the controller. The problem would be CAN or the engine controller.

If you are getting all the shifts, I doubt the CAN codes have anthing to do with your problem. A competent analysis of the adaptation data from the trans controller is required and possibly a removal of the pan for inspection of the fluid.
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  #3  
Old 01-25-2006, 08:22 PM
B52 B52 is offline
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Thanks Steve,
I do not know which controller sent the code, may have been the AAM or the Engine control module, but I did look up the code and it says "no communication with the trans control module from CAN" (words to that effect, I cannot remember the exact verbage)

I pulled the pan and the trans was spotless inside.

The problem is we cannot get the adaptation values out of the controller, because the data flows from the module through the CAN to the data link connector. The module isn't talking. How can I test to see if it is a defective module if it won't speak? I was hoping there was a way to bench test the module. But I guess the only way to find out is to buy a new module and try that. With my luck, the problem will be a loose wire somewhere after I buy a non-returnable special order part.
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  #4  
Old 01-25-2006, 08:41 PM
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Lets try this again, THE CAN PLAYS NO PART IN COMMUNICATIONS WITH THE DIAGNOSTIC TOOL. As I stated the first time all modules in a 98 ML except the transfer case talk straight to the diagnostic connector via hardwire NOT CAN.

Since you are shifting the module is working!. I would guess it also would communicate if asked properly, maybe not. Which controller can't talk to the trans controller? Does the code come back immediately if erased? Can you talk to modules other than the ME controller? What are you using to talk to the controllers?

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