Help with MSS54 DME CanBus Issues + Aftermarket Radios no longer operating

[s54brendan]

Hey all,

I’m having some issues with the CAN BUS in my car. As a result, my ABS, coolant temp gauge, and radio are not operating optimally/at all.

Background info: Last year, my alternator was killing my brand new battery. As a result, I got a white screen of death on my older aftermarket radio and my coolant temp gauge needle would rest on red. I quickly replaced the battery and alternator and the car has been fine since.

I tried installing a brand new AVIN Avant 4 headunit recently and that install didn’t go as planned. The unit receives power once you plug in the 17-pin adapter + CANBUS module with the car (Amber backlights come on for about half a second) and quickly cut off. Radio won’t power on. I put back the stock radio and with a few tweaks ended up working with no issues.

P.S. I replaced the amp in the trunk and verified all fuses and relays are working well so that can be ruled out.


My coolant temp gauge works but there’s no Amber backlight and if the battery is ever disconnected and reconnected, the gauge will act abnormally again (in the red). After a few drive cycles, it will return to normal.


I decided to scan for any potential codes with INPA and low and behold, a new error code showed up — Error 86: CAN-bus DME


I tried communicating with certain parts of the car such as the instrument cluster and INPA couldn’t even connect.




Then I took a look at the DME connectors and all seems to be ok. This leads me to believe that the transceivers for the CANBUS in the DME or any capacitors/transistors are fried.



Could the alternator frying my batteries (2) cause the DME to permanently lose connection to certain modules of the car? If so, is my best bet just grabbing another fully-operational DME? Car drives fine otherwise but I’d like to get this sorted out. Thank you!

[Shonky]

To be blunt saying things like "transistors/capacitors are fried" indicates not really understanding actual failure modes

The error is not present (Fehler momentan nicht vorhanden) and sproadic so CAN is probably ok. Clear it and see if it comes back. There's not a huge amount of CANbus in an E46. Mainly just DSC (inc steering angle sensor) and DME I think. And there's a dedicated CANbus for an SMG. I think this is a red herring. Pretty sure the "CANbus" adapters for the steering wheel buttons aren't even CAN. Aren't they on the K-bus only?

What was the actual problem with the old alternator? What does "frying" mean? Did it over voltage? If so, by how much? What does voltage read when engine is idling now?

The fact you can't communicate with KOMBI is suspicious. Depends a bit on what the alternator failure mode actually was.

Are you saying that removing the aftermarket radio interface and it all works properly?

[heinzboehmer]

Pretty sure the "CANbus" adapters for the steering wheel buttons aren't even CAN. Aren't they on the K-bus only?

Cruise control buttons are CAN, multimedia buttons are I/K bus.

[Shonky]

Cruise control buttons are CAN, multimedia buttons are I/K bus.

Not the same CAN as DME/LWS/DSC/KOMBI if it is. They connect direct to the DME is my understanding.

Edit: text indicates a direct connection from MFL-DME but on WDS I can't see it. Just K-bus to the MFL.

Edit 2: "All driver requested cruise control function requests are provided to the MS S54 from the MFL II control module in the steering wheel over a single FGR data lead."

Edit 3: It is direct, not CAN and it's not via KOMBI

[s54brendan]

To be blunt saying things like "transistors/capacitors are fried" indicates not really understanding actual failure modes

Well, that was the entire point of creating this post. Sorry for using half-slang to describe my situation lol. Power is being received to the respective areas, yet there is no response (i.e. radio). The alternator's voltage regulator was not operating normally and as a result, was in both undervoltage & overvoltage states. I don't remember the exact number figures as this was a year ago and did not write them down but the values were around 12.6 V & 14.8 V when I decided to randomly check. As a result, my fairly new AGM battery completely lost a cell and my coolant gauge started behaving strangely, followed by broken communication with the radio.

Again, sorry for using half-slang lol. When I said "fried", I'm referring to failed, degraded, and/or damaged electrical components. In this case, it could be a failed bus transceiver chip in the DME, failed or degraded capacitors, failed damaged circuit board traces due to heat or electrical stress (from alternator over/undervoltage states), voltage spikes/drops affecting the operation of the DME, etc. the list goes on.

With the new battery and alternator, constant voltage reading of ~13.8 V. It's been steady ever since.

Are you saying that removing the aftermarket radio interface and it all works properly?

I'm saying that any aftermarket radio I put in will receive power but will not operate (due to the CAN-BUS error (specifically iBUS comms operation in this case). I put my non-sat-nav OEM radio in and the radio works fine.

Now my main question at the end of the post is should I ultimately just grab a new DME or take the one out of the car and start inspecting the board and pins of the DME? Or are there any more feasible solutions

[heinzboehmer]

Not the same CAN as DME/LWS/DSC/KOMBI if it is. They connect direct to the DME is my understanding.

Edit: text indicates a direct connection from MFL-DME but on WDS I can't see it. Just K-bus to the MFL.

Edit 2: "All driver requested cruise control function requests are provided to the MS S54 from the MFL II control module in the steering wheel over a single FGR data lead."

Edit 3: It is direct, not CAN and it's not via KOMBI

Hmm, you're right. There's only one pin going from the DME to the cruise buttons, X60004 pin 27 "Data link MFL". Button presses are 100% relayed on the CAN bus though.

Weird that BMW would do a dedicated serial link instead of just CAN directly from the buttons.

Edit: I guess it doesn't have to be a serial link. Could also be a bunch of switched voltage dividers, which would make the direct link vs CAN decision more sensible. Anyway...

[Shonky]

Well, that was the entire point of creating this post. Sorry for using half-slang to describe my situation lol. Power is being received to the respective areas, yet there is no response (i.e. radio). The alternator's voltage regulator was not operating normally and as a result, was in both undervoltage & overvoltage states. I don't remember the exact number figures as this was a year ago and did not write them down but the values were around 12.6 V & 14.8 V when I decided to randomly check. As a result, my fairly new AGM battery completely lost a cell and my coolant gauge started behaving strangely, followed by broken communication with the radio.

Again, sorry for using half-slang lol. When I said "fried", I'm referring to failed, degraded, and/or damaged electrical components. In this case, it could be a failed bus transceiver chip in the DME, failed or degraded capacitors, failed damaged circuit board traces due to heat or electrical stress (from alternator over/undervoltage states), voltage spikes/drops affecting the operation of the DME, etc. the list goes on.

With the new battery and alternator, constant voltage reading of ~13.8 V. It's been steady ever since.



I'm saying that any aftermarket radio I put in will receive power but will not operate (due to the CAN-BUS error (specifically iBUS comms operation in this case). I put my non-sat-nav OEM radio in and the radio works fine.

Now my main question at the end of the post is should I ultimately just grab a new DME or take the one out of the car and start inspecting the board and pins of the DME? Or are there any more feasible solutions

14.8V is not going to kill an (nominal 12V) automotive component or "fry" them in your words. Your slang doesn't help and (again) frankly you're just guessing. Your possibilities list is unlikely based on the history provided.

I would not replace the DME. There is little pointing to that being the problem.

There's no CAN bus at the radio. So I'd stop looking at that.

What does the aftermarket radio do without the interface attached on either side? Main thing it does is relay button presses to the radio and is not even needed to operate.

Do you know if the radio works properly in another car? You should be able to power it up on a bench if you have a power supply? Even without I-bus it should still mostly operate and boot although I'm not sure if they have an accessories feed to wake them.

Is it second hand, factory refurb or something - why is the knob missing?

[Shonky]

Hmm, you're right. There's only one pin going from the DME to the cruise buttons, X60004 pin 27 "Data link MFL". Button presses are 100% relayed on the CAN bus though.

Weird that BMW would do a dedicated serial link instead of just CAN directly from the buttons.

Edit: I guess it doesn't have to be a serial link. Could also be a bunch of switched voltage dividers, which would make the direct link vs CAN decision more sensible. Anyway...

Yeah not sure why it couldn't just relay using the KOMBI as the interface if the DME wanted it via CAN. Maybe a safety reason they didn't want the KOMBI going out to stop cruise being cancelled by the buttons? Seems pretty far fetched though. It already had the smarts for the K-bus so why not just use that rather than re-invent the wheel.

[s54brendan]

14.8V is not going to kill an (nominal 12V) automotive component or "fry" them in your words. Your slang doesn't help and (again) frankly you're just guessing. Your possibilities list is unlikely based on the history provided.

I would not replace the DME. There is little pointing to that being the problem.

There's no CAN bus at the radio. So I'd stop looking at that.

What does the aftermarket radio do without the interface attached on either side? Main thing it does is relay button presses to the radio and is not even needed to operate.

Do you know if the radio works properly in another car? You should be able to power it up on a bench if you have a power supply? Even without I-bus it should still mostly operate and boot although I'm not sure if they have an accessories feed to wake them.

Is it second hand, factory refurb or something - why is the knob missing?

As I stated earlier, this was at random deciding to check the voltage (car was operating ok at the moment) and the voltage reading was 14.8. This is still at an overvoltage state despite the car running fine. I wouldn't be surprised if the car at one point read above 14.8, especially when the car started acting out. So yes, the possibilities list is indeed possible as that was the root start to these problems.

Yea no CANBUS to the STOCK radio. Most aftermarket radios you purchase come with a CANBUS module. Why? Well when you replace the factory radio with an aftermarket unit, the aftermarket unit most likely does not communicate digitally. Hence, a harness adapter + the red can-bus decoder boxes that come with these radios is needed to convert those digital signals into analog 12V signals that the radio can use.

Yes, the radio (new Avin AVANT 4) works on another car perfectly fine. I transfer it to my car, and you can tell power is being received with the amber backlights being present for a mere half a second. Then, there's nothing.

Is it second hand, factory refurb or something - why is the knob missing?

This is a completely different radio (Eonon headunit that was already installed when I purchased the car) than the one I mentioned (AVIN Avant 4). The AVIN is a brand new unit. The Eonon was working perfectly fine. The white screen came when the alternator and battery were acting up. That radio has never worked since. The knob is missing because those plastics are fragile. I got out of my car and accidentally hit the knob and have yet to find it lol. Not sure how that would play into this problem but yea.

[Shonky]

Good luck fixing your problem. Sounds like you've got it all covered.

[s54brendan]

Good luck fixing your problem. Sounds like you've got it all covered.

Yep each condescending reply of yours is getting me one step closer to the solution

[elbert]

Most aftermarket radios you purchase come with a CANBUS module. Why? Well when you replace the factory radio with an aftermarket unit, the aftermarket unit most likely does not communicate digitally. Hence, a harness adapter + the red can-bus decoder boxes that come with these radios is needed to convert those digital signals into analog 12V signals that the radio can use.

Sorry if you mentioned this earlier, but did you try *completely* removing the harness adapter and canbus adapters, then seeing what happens?

[s54brendan]

Sorry if you mentioned this earlier, but did you try *completely* removing the harness adapter and canbus adapters, then seeing what happens?

All good, yes I did. In addition, I went and sourced a brand new harness adapter and new CANBUS decoding box. I clipped the harness adapter into the HU and you can tell power is received to the unit but the signal last for about half a second. Then there's no sign of life. Leads me to believe there's a wire on the main harness that's not seating correctly but one can check it so many times

I proceeded to plug this unit into my neighbor's e46 and all went well. My car last year with the whole debacle also had the wipers come up and remain stuck half way. This also leads me to think I may need to service my GM5 module. Then again, no codes for that and all works well ever since replacing the alternator and battery. Now it's the CAN-Bus connection with the DME I'm trying to sort (if that makes sense). I can't communicate with a few modules in the car via INPA now.