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Discussion Starter · #1 ·
2003 330CI vert

The car has been sitting in my driveway while I figure out the no crank issue.

I left this morning and everything was normal, came home 3 hours later and the rear brake lights are on, as if someone was stepping on the brake pedal. The weird part is that I have not touched the car in almost a week...

Disconnected the battery for now until I figure this out. Any suggestions where to start looking?
 

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Discussion Starter · #3 ·
Was going to take a look at the switch so I connected the battery and my dash was also lite up like a Christmas tree... Key is not in the ignition..
 

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Brake peddle switch is my first guess but check for water shorting out somewhere. Perhaps your taillights have water in them?
 

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I was also going to ask if there was water or moisture in the car anywhere?
 

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Ignition switch. Same thing happened to me. As jfoj mentioned, make sure there is no water getting into the car. Check under the mats. Moisture will mess up the ignition switch.
 

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tony,

Did the moisture/ignition switch problem only impact the lights on the dash or did it also cause the brake lights to come on?
 

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Check the tail light connector for corrosion, the elephant trunk and ignition switch. I had the same problem and all three had issues.
 

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Discussion Starter · #11 ·
There is enough moisture getting in to fog up the windshield on the inside. My guess is the seal between the top and the body. However, the floor mats themselves and and carpet underneath are completely dry. This is even having 2 feet of snow on the roof and heavy rains. I will check the tail light connector also. Luckily my truck is also very dry.
 

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So I have a neighbor that is away for 3 months, last week I get a call from another neighbor that the brake lights are on in the E46 in the driveway.

I tell them to get the key ASAP and I grab my tools and over, worried that maybe the LCM may be one of these to catch fire.

So I see the drivers side windshield has a fair amount of condensation on the inside.

I disconnect the battery and then think to myself we did have a bunch of rain a few weeks ago. I looked and the driver side door sill plate has water on it, so I know the driver side inner vapor barrier is leaking.

I reconnected the battery after a few minutes and the brake lights were still stuck on, I pulled upward on the brake pedal and no change, pushed down and pulled up on the brake pedal, no change.

So this was about 10 days ago, I have aired the car out a bit, but not connected the battery back up.

I will try to reconnect the battery today and see if the brake lights come are still on, if they are off.

If they are off, clearly the moisture was the problem!!!

I was searching around for similar situations to see if there were other instances. I am guessing the moisture may get on the LCM module and cause havoc? I do not recall if the LCM has the silicon conformal water proof coating like the GM5 module, if it does not, this is not good. I have seen other electronic boards in cars that did not have the silicon conformal coating and if moisture got in the car, the solder would oxidize. Lead Oxide is the white blooms that appears on the solder joint. Lead Oxide is conductive and if there are close circuit traces or there are multi pin surface mount logic chips that have very close leads the Lead Oxide can short out these connections and cause crazy things to happen.

The good news, is if the board has Lead Oxide blooms on it, you can take and old tooth brush and just scrub the solder joints with a dry toothbrush and blow the board off with compressed air.

You can also search and buy Conformal coating spray online as well, not sure many local stores would stock this, possibly electronic supply stores. Some of these are stupid expensive via Amazon but you have to search carefully.

Here is a reasonable priced product - https://www.amazon.com/gp/product/handle-buy-box/ref=dp_start-bbf_1_glance

Hey in a pinch, there is always Flex Seal in a can clear spray option!
 

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I do not recall if the LCM has the silicon conformal water proof coating like the GM5 module, if it does not, this is not good.
I texted you the pictures of a spare module I had laying around. It looks like the LCM is coated. However, if water gets into the harness plug, it could short the pins inside the connector.





 

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tony,

Did the moisture/ignition switch problem only impact the lights on the dash or did it also cause the brake lights to come on?
I had warning lights on the cluster and the brake lights lit up on both sides with no key in the ignition. Tried disconnecting the battery a couple of times for a few hours at a time, and still the same issue. I then removed and reinstalled the ignition switch and the problem went away for a couple of days, so i replaced the switch with a new one and haven't had an issue for several months now.
 

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OverBoost, thanks for the pictures. Appears that the LCM does have a conformal silicon coating on the circuit board.

Here is what I suspect happened to my neighbors car.

Been sitting at least a few weeks, we did have a few days of heavy and long duration rain.

A few days after the rain, brake lights were on in the car, I do not think the dash lights were on. I disconnected the battery, but after about 15 minutes connected it again to see if the brake lights were still on and they were. So I disconnected the battery and the car has been sitting.

Found condensation on the drivers side lower front windshield. When I opened the drivers door the sill plate was wet, so clearly there is an inner vapor barrier sealing issue.

Car also has a sunroof, lives outside most of the time.

I suspect that moisture may be getting on the LCM, probably in the top connector??

I aired the car out for a few days, no more condensation on inside of the windshield.

Reconnected the battery today as a test, NO BRAKELIGHTS!

The only thing that has changed is I dried the inside of the car out, it has not been started or driven in close to 6 weeks at this point.

There have been a number of E46 fires that have centered around the LCM so I also suspect these LCM fires may be due to water or water damage and corrosion.

I will probably need to research the brake light problem a bit more to see if my hunch is correct.
 

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Discussion Starter · #16 ·
jfoj, like you I let the car air out. Last night there was no condensation on the windshield so I reconnected the battery and the brake lights and dash lights were off. I am going to try and clean up the ignition switch to see if maybe it is just a little corrosion on it..
 

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Neighbor returned home. Car was died out. Battery was low but good. Charged battery and brake lights are off.

At least 2 door vapor barrier are leaking and maybe sunroof drains clogged.
 
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