Had my 2010 L322 5.0 NA in the garage for about 6 weeks - I was replacing the front coolant pipe but I was delayed when I snapped some plastic. When I reconnected the battery to wake her up, I got a black instrument panel except for "smart key not recognized." It'll turn on and run just fine on the second press of on/off when I hold the key in the emergency position, but IPC is blank, TFT is blank. At first I was sorta excited - finally, a reason to get a proper scan tool!

IID BT G3 showed up and gave MS CAN codes from the IPC and the CJB (BCM), Both units gave U0010-88 MS CAN "bus off" codes, and the IPC also gave a U0018-00 MSCAN bus (-) shorted to bus (+). NONE of the modules on the MS CAN are showing up when scanning for ECUs [except those which are scanned via HSCAN, i.e. ICP and BCM]. Patrick at GAP suspects a wiring issue, probably water ingress he thinks. I've got access to a proper shop manual and wiring schematics, connector views and pinouts, etc.

So far, I've searched the forums and I've read the posts of buck66, kevrobbo1961 and Stuart-. I checked the location near the parking aid module in buck66's post, but my yellow/white yellow/blue twisted pair drops straight down in a big bundle and doesn't go around the metal bracket that cut into his wires.

When I check resistance at the diagnostic socket on pins 3 and 11, I get 59.9 or 60.0 ohms. When I check resistance to ground (passenger's footwell was handy, and looks shiny brand new, all dry down there btw) from either pin 3 or 11, I get open circuit. I think this means that the spine wiring of the bus is healthy, both 120 ohm terminal resistors are being seen from the diagnostic socket, and also that the two connectors which are in series with the spine of the bus - the driver's and passenger door connectors at C0322/C0463 and C0336/C0459 - must also be intact and healthy.

So what's the move? My thinking right now is that since the wiring seems OK, I should be looking for a faulty module, just "unplug and chug". Since mine wasn't fitted with the Companion cam, there's only 16 possible modules that could be at fault . Does anyone have a suggestion of where to check first, or of other electrical measurements I can make? In the absence of any likely suspects, I'll probably go in order of ease of removal.

Other possibly relevant info: a couple days prior to garaging it for the coolant pipe repair, I had noticed the rear passenger door refusing to electrically lock/unlock from either key fob button presses, nor central lock button. Manual lock/unlock was OK. The AC had also just began operating at reduced capacity, not getting very cold - prior it had always worked perfectly. I had checked pressures in the garage just before the coolant repair and they seemed normal. If the CAN bus issue was caused by water ingress, I think condensate drainage from the evaporator would be the mostly likely source.

After a closer look at the MS CAN wiring diagram, I decided to use the driver's and passenger's door connections to try to isolate the network, and now things are narrowed down a bit more.

Unplugging the driver's door electrical connector (in the flexible rubber boot in the door hinge where it meets the body) detaches the IPC and the diagnostic socket from the rest of the MS CAN system (and removes the driver door module from the MS CAN entirely). If testing this had fixed everything, it would imply my IPC or wiring nearby was the source of the CAN trouble. I unplugged it, re attached the battery, nothing happened. Pfew. IPC, diagnostic socket, and driver door modules are probably OK. I unplugged the battery, reattached the door connector.

Unplugging the passenger's door connector isolates the climate control module, audio head unit, and companion camera if fitted. I did that and then reattached battery and BAM right away the radio came on and the climate unit started blowing air. So the BCM is good, the audio head unit is good, and the climate unit are all good, and their CAN wiring is good too.

I also tried unplugging the MS CAN-containing harness at the passenger door module, and everything stayed dead. So I think that module is ruled out for now too.

I've got 16 down to ~10, and I've ruled out most of the things that would cause me to need to take apart the dash thank goodness. Help is still welcome and desired, but I'm happy to be making some headway. Next is the mirror, then either the blind spot monitors or the seats.

It was the KVM all along!

As I was going around one by one to all the devices on the MS can network unplugging them, unplugging the canbus-containing harness from the KVM totally worked, and everything came back on, IPC even showed the milage (sent from bcm from the other end of the MS.can network). Suddenly my iid tool could scan dozens of new ecus. Feels good.

eBay has tons of replacement KVMs for cheap, and I think the IID tool can do the replacement programming, so I think I'll try that instead of giving $500 to the stealer.

Anyone know if I need to buy one with the same exact module number? Mine says AH42-19H440-AE but others on eBay might an AG suffix, would that be OK?