MSS54hp DME canbus issue?

[nextelbuddy]

I recently picked up a few HP DMEs from someone local and said they were bad. Each of them were marked with what was wrong

One of them was marked in sharpie that said can bus issues

I hooked up my BDM tool and did an erase and flash and flashed a complete stock MSS54hp full binary file.

Modified the tune file for SMG and EWS delete.

Loaned it to somebody that had an SMG car and they reported that the DMV did not work and they were getting smg codes for the pump, the shift solenoid and something else SMG related.

Didn't really make a lot of sense to me other than the fact that SMG communicates via CAN bus to the DME

I repaired their original DME which was what their problem was.. They bricked it with mssFlasher by virginizing it.

I used BDM on their DME and flashed A complete stock file changed it to SMG, updated their VIN, gave it to them and they were good to go

So going back to the DME that I loaned them with can bus issues. I don't understand what on the DME is specific to CAN bus exactly

So this leaves me to believe there's something else on the DME outside of the two master and slave. EEPROMs

Was wondering if anybody had any clues or ideas as to what else on the DME could be affected that would cause CAN bus issues specifically

Scratching my head because I hate to trash a DME just like that.

[Bry5on]

Look for the CAN transceiver(s) on the PCBA, trace the circuit to the DME or IC pins. Reflow solder on all the connections in the chain. If there’s still an issue, replace the transceiver(s) or check reference specs for the transceiver to make sure resistors and capacitors are functioning as intended. Good luck.

If you get too frustrated, heinzboehmer or I will take it before it goes in the trash as an extra spare (we both have spares already)

[nextelbuddy]

So where does one find out what is what on the PCB? I don't know what the can bus receiver looks like to do a trace, is there something online that shows what a generic CAN bus receiver looks like on an automotive PCB? Is there something S54 specific that shows what the labels are for the circuits on the PCB?

[heinzboehmer]

Start looking up datasheets for the part numbers you see on the board

Or trace the CAN lines from the DME connector. They're bound to end up at the transceivers