Well it all started with the typical dash lighting up like a Xmas tree, gauges going down, no radio, windows, doors etc. Only exterior lights & interior lights. Once turned off will not start. No cluster power nothing.

spent 2 weeks checking every wire fuse bcm pcm clean grease etc. Battery was fine and an expensive oddessy but replaced with a bigger better oddessy, already had a mechman alternator from winter purchases as well as the big 3 upgrade. Then to the starter just to be sure. Tested all power and grounds they were fine before and after installs. Car was still dead.

last minute I decide maybe if I get all the doors closed and let it reset she will wake up. Nothing. So it had a shop day already schedule for some performance work so I had given up. Then I thought oh I should take the sub box out for the shop so they don’t have to work around it and I have room for the parts. Keep in mind it is not hooked up never has been I just bought it over winter the dual 8” subthump box with 2 8” kicker subs. Take it out and when I walk by the car I see the lights flash to lock. Wait a minute check fob and it works everything works. Didn’t think anything of the subs.

fast forward a month or so and I’m installing a new carbon hood and front splitter some splashes etc and get the car all detailed and think hey I should put my box in and get ready to install the audio system. Go to can tire wit wife and immediately it starts with the issues. Run home take box out. No problems.

so after that long winded blurb, my question is do I have an issue under the carpet and maybe something is shorting or maybe are the magnets messing with the fuel pumps or the antenna or creating RF noise messing with the car. I find it strange as out of all our problems never heard of this one. I only figure it out the other day and havent had a chance to tear out the rear carpet and inspect. Cub box is custom built to fit the c6 perfect and they are only 8” subs but have a decent magnet.

other question is if it were a magnet issues would dynamic mat help or fix the problem. Either way any help or just a general discussion on anyone having any similar issues. I have an aftermarket head unit which functions fine and no other issues these days except the odd typical key fob on the dic but it has always started except once for not recognizing key fob but after a few minutes it woke up.

Thanks for any help on this. Long time reader first time poster, this site has helped me greatly when it comes to help with figuring certain things out. Hope you all have a great day.


I forgot to post my car details so it is a 2005 coupe A4 modified corvette. Only thing I haven’t touched yet really is the heads, lifters & bottom end. It has a stage 2 comp cam with appropriate mods that go along with that springs, reunions, etc, intake, fast intake manifold , NW 103 TB, LS3 MAF, all new under the hood, battery, wires, terminals, clamps, plugs, wires/covers, harmonic balancer, water pump you name it. Full header/exhaust, rebuilt torque tube, billet built transmission/TC, all the fluids & motor work/tuning was done by corvette shop, and lots of cosmetic restorations and upgrades inside & out which have nothing to do with this thread lol. It’s a build I started in August 2021 and continue with it daily lol. For most part never given me any real electrical issues.

 

I would attach a Tech 2 and retrieve DTCs from every module. Many DTCs including network comms errors will not result in a check engine light.

Something to consider. The radio is on the Class 2 bus along with the RCDLR, instrument panel, and other systems. If your aftermarket radio adapter is malfunctioning, which they frequently do, it could be stomping on the Class 2 bus, preventing the car starting.

 

The aftermarket head unit has been in for a while. The sub box was just sat in hatch unhooked. No other audio mods. Sub box in problem sub box out no problem. Everything works fine every day unless I just sit the box in the hatch though.

 

Do you happen to notice this issue specifically after a car wash or rainy day by chance? I ask because mine had similar issues and it was all due to water flooding into the passenger foot well through the air box, which then got into the BCM causing all kinds of problems. I was lucky as heck and no fuses were popped and the BCM was fine.

If you notice the passenger footwell carpet is wet, that may be the issue. I had to pull the drain udder and clean it out of all the nasty gunk from years of build up to solve it. Might be worth a check.

 

no leaks. Been through all of that. It only happens if I put the sub box in the hatch. Not hooked up. Just sitting there with subs in the sub box. That’s what makes it go crazy. So thinking either magnetic issues with something or a wire under the carpet. Just hoping someone out there has had this happen before. Thanks for the reply though much appreciated.

 

How correlated are we talking? Once or two times, or will the car start a hundred times out of a hundred without the sub box and fail to start a hundred times out of a hundred with the sub box? Are there confounders like the hatch being open, or it being a cold morning, or something else?

 

drives & starts perfect 100% of the time. It once didn’t start 2 years ago for a key fob error and tends to say there is no key fob but always has started. It is in direct correlation with the sub box. No box perfect starts. Box instant dash light up acts up etc. So 100% correlates to the box being in the car. No power to subs no amp in car have t even began installing the stereo yet lol

 

I'm curious how many times you've tried this.

 

several to confirm it was the problem.