I-Bus Issue - LCM and IKE not talking?

[spngr311]

So I've got a fun intermittent issue. We have had a ton of rain the last 3 weeks and my 2000 540iT has been evicted from the garage while my Z3 goes back together. I thought I solved this issue about a year ago with a new cluster, LCM, and sunroof, but something is tripping it up again. The symptoms are annoying: turn signal indicators on the cluster do not work, fog light indicator does not work, the turn signals do not flash when the car is locked or unlocked, or the signals flash constantly after the car is locked/unlocked, self leveling headlights aren't doing their thing, and the reverse lights do not work. The lights are all functioning otherwise on the outside of the car, with the exception of the reverse lights. Sometimes, this goes away and the car functions normal, but it has been like this for a week solid now. I'm going to put it on a computer tonight if the rain lets up enough to see if I can pull any codes, but previously, I'd get a communication error. Is there a connector somewhere I should check for water intrusion or something loose?

[DHoang]

there's a fuse block with a bunch of connectors under the passenger seat that gets corroded if there's water intrusion...

this post shows problem areas..even though it's for an e38, same deal for e39.
https://www.bimmerforums.com/forum/s...nder-pass-seat

[spngr311]

I will take a look in the area, but I don't think I have a power problem. The lights do function outside the car, just it isn't communicating that info back to the gauge cluster. The signal stalk sends a signal to the LCM and that operates the lights (same with the headlight switch). The LCM then tells the cluster what it is doing. That is where I am seeing a drop. The cluster still displays all of the other info (speed, rpm, and even lights up).

I have also had some miscommunications from the seat belt monitor to the dash where it will keep the message 'fasten seat belt' on even when my belt is fastened. So now it looks like maybe the K bus too?

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[spngr311]

Checked inpa and all that and it cannot communicate with the LCM and PDC (though this seems more intermittent as it did get part of a signal from it). Some other threads said the LCM is in a limp mode, but is that indicative of a dead LCM? Can the limp mode be cleared?

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[geargrinder]

All of what you're looking into is on target, springerspaniel.

A bad module can take the (one of the... several of the...) bus down. Or just a shorted wire... or a bent connector pin..

A good trick is to check things like your steering wheel buttons and emergency flashers ... if those work OK then maybe its not the bus... if they are all acting up... then yeah... look at the modules.

LCM's have been known to die and take down comms. Also GM's (other bus, in 2-bus cars...) Also the IKE can have bad connectors / cracked/cold solder joints that screw the the connection, and they are the gateway for comms there too.

Don't completely rule out the floor area BTW, that is known not just for causing 'no power' but for causing other electroweirdniz.

Good luck...

[spngr311]

So I did more investigation tonight. I had a spare known good unit (actually worked yesterday during a brief test - didn't have time to code it so I didn't want to leave it in) and that unit was not working today. The hazard flasher works, and so does my cruise control. The radio buttons are sporadic normally since I have an aftermarket unit.

I checked the white yellow grey wire for continuity between the LCM and the terminal block and it was good. I think that is the communication wire.

I had a very brief moment where BMW scanner was communicating with it (flashed like it was working in pasoft then hung up).

The gm3 felt a little hot this evening when the lighting wasn't working right, and it flashed properly this morning when I unlocked the car. PDC is also not talking/working either.

One other place I am going to check is the wiring harness on the hatch. It is looking a bit rough. Any thoughts that a wire back there could be causing issues? I have the Schneidman harness ready to go, so I may try that before I go further on the module hunt.

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[Bmwe39528i1998]

Did you fix it?
Did you consider / test ibus wire between lcm and cluster?