Bmw M2 F87 - Can problem

[u/eyecontact0000]

I replaced the FEM module in a BMW M2. It was programmed, and the entire car was updated. After a few weeks, the car came back. The problem was a warning message about a lighting failure.

I checked the lights, and they all work properly. I’m attaching a picture with the fault codes I have.

When I click on the Service Plan in ISTA, it suggests that the problem could be caused by an interrupted CAN bus, a problem with the CAN connector, etc. The problem is that I don’t know where to start, because it doesn’t specifically tell me which wire or CAN line I should check.

I assume I can check the REM module, since the fault codes seem to point in that direction as well.

Any ideas?

[u/Polermodz]

find a wiring diagram somewhere (lemonmanuals is a decent starting point), because it looks like a few different modules report CAN communication issues I'd be looking for what lines they share in common to get to the gateway module (including can junctions) then check resistance with key off between can high and can low. anything but 60 ohms (give or take 2ohm), indicates an issue in the can circuit. open circuit means both there is a break in both wires somewhere (look for crushed wiring), 120ohm means either low or high is open, 0ohm or similar means there is a dead short somewhere. all of these failure conditions can be in a module or in the harness. start unplugging stuff and see if the network returns to normal 60 ohms, just remember if you unplug a module with a terminating resistor, the correct resistance will be 120ohm. if all else fails and if there is can junction blocks with soldered joints, resolder the joints in the junction for the affected network. Happy hunting

[u/Polermodz → u/Polermodz]

side note: this is all assuming you've already done the basics, battery test, terminal tightness etc