Help! Gauges intermittently die, everything else works fine.

[Mateospeed]

Folks, I'm having an interesting problem. My 2008 135i has decided to do something new: Let me drive with no gauges! It will not pop a light up that tells me my TPMS is "Inactive." Whatever that means. Then, while driving, my dash will either completely shut off for a few seconds, then come back to life, lit up like a christmas tree, with a bunch of warning lights, then shut off again. Then it might come back on and go crazy, with jittery needles and inaccurate readings. I have also noticed the turn signal indicators and sounds do not work while this occurs. I can't tell if the lights themselves are working, as this has so far only happened while driving. If I shut the car off and re-start, it cranks (very quickly) for a long time before firing.

Whenever this happens, the car drives along fine. No other systems seem to be affected - I'm just driving blind.

I suspected a bad battery, as my indicator was black, and it was the original battery. I replaced it yesterday, which made absolutely no difference.

Seems very much like an electronics failure, but where? Any help will be appreciated!

Also, I avoid stealerships whenever possible, so I want to try everything possible before handing it over, so please don't just say "take it in."

Thanks!
-Matt

[smrtypants44]

This happened to me. It has turned out to be water got in the trunk via the tail lights and was intermittently shorting the module back there.

[zx10guy]

I had this issue too. Mine turned out to be a shorted junction box. Don't know exactly how water got there and shorted it. I suspect it was due to something the body shop did as I had it in there for minor repairs. That incident was about 3 years ago and hasn't popped back up since.

It was sneaky as there wasn't any definitive code flagging it. They were able to figure it out when my car acted up for them again. They kept the car running in this state and threw a oscilloscope at it which they then traced to the junction box in the trunk. Car was in the shop for I think a week. They also found the comfort access module not working correctly either. Didn't bother asking them if the short had caused the CA module to fail too.

[zx10guy]

Here's the part number for the junction box that was replaced:

61-35-9-305-739

[Stewy_604]

OP, did you get this solved?

[TwinTurboXI]

Originally Posted by smrtypants44

This happened to me. It has turned out to be water got in the trunk via the tail lights and was intermittently shorting the module back there.

Same thing happened to our e90. It ended up being a TPMS module near the trunk that caused all sorts of intermittent electrical issues.

[Mateospeed]

Update: Did finally get this resolved with the help of my favorite indy shop (screw the stealership). They found water in the area on the passenger side of the trunk, under the floor mat, right behind the wheel well. The trunk was dry, there was no evidence of water intrusion from anywhere, including the tail light. So, that's a bit of a mystery...

BUT, what happened was: about 8 inches of water in that area, covering the Tire Pressure Monitoring System (TPMS) Module. It died, as you might expect, and caused the entire serial network (CAN) to go down. So, everything started going nuts.

We drained the water, drilled a small drain hole, and replaced the module. $750 (about 50/50 parts/ labor), and everything's back to normal. Honestly, I expected $1000's, so I'm pleased. I also really like this shop, so I'm happy to pay them for their time. So, props to Motorsport Connections in Winston-Salem, NC.

Anyone that has a similar problem, go hunting for water intrusion in your trunk area. Apparently, it's tough to find and get to, but there are several electrical components in that general area that can fail due to water damage.

Happy hunting!

-Matt

[Stewy_604]

^^^ I had water in this area end up taking out the Comfort Access module. I thought for sure it would've been the tail lamp that was leaking. The source ended up being the c-pillar drain tube was feeding water directly onto/into the ventilation flap. Thinking the body shop did this (hopefully by accident) when they had the car in for a rear end impact last year.