E39 Randomly Loses 12v Power

[trevzor4242]

So recently after a laser jammer install and an electric exhaust cutout install my car has started with a weird issue. Randomly it will lose 12v power. Sometimes the amp cuts off and while driving the speakers go silent for a couple seconds, sometimes when I get in the car after a while the radio has lost power, because it prompts me to enter the language - something it does after power loss. Today, on a 3 hour drive the dash warning lights all lit up for a split second then went back to normal. I've also had it stall on me twice now too and the issue is becoming more common. It started as a once a week occurrence, now it's daily. Sooo, I'm unable to find the source of this issue. I don't know if it's related to the recent installs but it's certainly possible.

The exhaust cutout just tapped into the battery and is fused so I don't think it would affect it. Battery terminals are tight.

The laser jammer install involved routing a wire through the firewall, so I had to run an additional wire through the drivers side grommet. I didn't cut any wires, I sealed it all well, and the only thing I could've done there is move things a touch so a possible frayed wire maybe got worsened.

Today made me more confused. I figured if it was related then I did something to hurt the wires that enter the firewall. So, I pulled the tape off the wires there, and found a very very frayed ground wire. Pictures are attached. This one specific wire evidently got extremely hot. The insulation melted for almost the whole section I could see, and many spots had exposed wire. I pulled about 3ft of tape off and crimped on a replacement wire here as close up to the firewall and other side as possible. This wire goes from a ground terminal at the oil filter all the way into the firewall and I don't know what after that. It is brown with a stripe of black. Just as a note I turned on the car with the cable cut and the radio still powered on. Hmm. Sorry the Pic doesn't show it all undone, I was caught in the moment and didn't take better pics. But, that wire was baaaad. The Pic shows exposed metal wire out of its insulation, and melted through electric tape.

Drove it after and had the same issue... So, my problem persists and I have no idea what's happening.

Any help is appreciated. Thanks

[Jaaap]

Something is drawing more power than the wires can handle.
That can trigger burnt wires and the car cutting power to non-essential parts (at first) or essential parts if the voltage drops low enough.
Don't start replacing wires yet, find the root cause first.

STEP 1 DO THIS IMMEDIATELY:
Remove the power from both the laser jammer and the exhaust cut-out immediately.
Do this by disconnecting the wires where you tapped into the power, so on the car side, not the jammer/cutout side.

STEP 2 Find out if there's a short to ground somewhere
Fire up INPA and read all the modules. You can list the error messages here.

[trevzor4242]

Wish I had that, all Ive got is a Bluetooth obd2 module. I don't think I can read any detailed codes like that, only see some sensors and CELs. As for the jammer, I tapped into the car phone power under the center console so I can check that out soon.

[jclausen]

Because the car uses bus systems tapping into a wire may not be the best thing to do I would unplug all the mods and see what happens these cars don't like things tapped in to the wrong system

[trevzor4242]

Because the car uses bus systems tapping into a wire may not be the best thing to do I would unplug all the mods and see what happens these cars don't like things tapped in to the wrong system

I don't know why that would hurt it but I guess that could be something to do with it. Don't want to dismiss a possible solution. From what I had read tons of people tap in to that car phone power, it's switched, fused, and jammers (should) use less power than a big brick phone. Where else would I even connect to for key switched power if not on the bus system?

[trevzor4242]

Anyways, today when I get home I'll disconnect the exhaust valve and laser jammers at the connection and see if the problem is still around, this could be a weird coincidence but I won't know til I disconnect everything.

[JimLev]

Tapping into any 12 volt wire should not cause any problems with any bus. All of those 12 volt feeds are either directly connected to the battery or thru fuses/relays that connect to the battery.
Did you find any blown fuses when you were investigating the melted brown wire?
Have you dropped the fuse block down that is above the glove box to see if there are any loose/bad connections there?

I have 5 or 6 different things tapped into switched and un-switched 12 volts in my car, never had any problems.

[trevzor4242]

Tapping into any 12 volt wire should not cause any problems with any bus. All of those 12 volt feeds are either directly connected to the battery or thru fuses/relays that connect to the battery.
Did you find any blown fuses when you were investigating the melted brown wire?
Have you dropped the fuse block down that is above the glove box to see if there are any loose/bad connections there?

I have 5 or 6 different things tapped into switched and un-switched 12 volts in my car, never had any problems.

Haven't checked that box, only the one in the trunk and nothing was apparently bad. I'll look over all fuses, disconnect the jammers and exhaust valve when I'm home tonight.

[trevzor4242]

Update: I checked all fuses, none blown. I disconnected the power leads to the exhaust valve and haven't gotten the issue yet. Hard to say without a few weeks of driving whether that was really the fix but so far it's looking good.

Also, probably unrelated... Today I backed into a space, idled for a bit and when I shut off the car the dash gave me a "engine failsafe prog" code. I've never gotten the code before, and I couldn't recreate it by starting the car again, and no engine lights ever came on. I'll give it a once over and try to get any codes I can eventually.

This car is very well maintained although getting up in mileage (144k) I've not had any real issues til now.

[trevzor4242]

Well I just bought a USB 16 pin obd cable, and at home I have a 20pin to 16 pin adapter. Hopefully this will give me some good diagnostic ability. My only laptop is mac but I can run a virtual machine or borrow a windows laptop.
What's the cheapest software that will do the job for a 2000 540i?

[JimLev]

INPA should be a free download if you google it.

[trevzor4242]

Well I thought this issue was gone but of course it came back. Stalled during parking today. Engine just shut off completely and there was no electrical power either. Not anything.

Turning the key on didn't light a single thing on the dash. It was dead in the water. Waited about 30 seconds and tried putting the key in and out and eventually it came back like nothing happened. Battery terminals are clean and tight. What fuses/connections could cause a complete power loss to the electrical system?

Also, I got an inpa cable and despite trying like 6 downloads, they all ended up broken. I've read that many others experience this and the surefire method is to install standard tools via CD. That's in the future but not my concern now.
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[jicaino]

It looks like your ignition switch could be having some issues...

[trevzor4242]

It looks like your ignition switch could be having some issues...

Interesting. It's such an intermittent issue it's really hard to troubleshoot.

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[jicaino]

Sometimes they'll go like that, starting with random shorts and disconnects. In the meantime, you plug and unplug stuff and since the fault isn't coherently repeatable, you can loose a huge amount of time diagnosing and or blow a crapload of money throwing parts at it.

[trevzor4242]

Sometimes they'll go like that, starting with random shorts and disconnects. In the meantime, you plug and unplug stuff and since the fault isn't coherently repeatable, you can loose a huge amount of time diagnosing and or blow a crapload of money throwing parts at it.

Do you know how tedious the replacement would be? Could I change the switch without changing the lock?

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[jicaino]

Do you know how tedious the replacement would be? Could I change the switch without changing the lock?

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It's fairly straightforward but it requires a lot of dissasembly in the steering column. Yes you can use your lock, you can extract it with a thin drillrod blank (around 1.2mm diameter, and more than 6 cm long, insert it in a keyway you'll see right below the revolving part of the lock cylinder, bend it at an L angle leaving about 5/16" from the face of the cyl, insert the key along with the pin, rotate it between ignition 1 and ignition 2 and feel for a springload lock that you "pick" with the wire and it comes out. then you disassemble all of the electrical side from down into the column guts and replace just the electrical connector.

[JimLev]

No need to remove the key lock tumbler to change the electrical switch part. That is on the left side of the steering column.
Have you checked the fuse block under the carpet on the pass side? All power for the cabin goes thru these fuses.
They could be corroded if there was ever water leaking in on the carpet.

[trevzor4242]

No need to remove the key lock tumbler to change the electrical switch part. That is on the left side of the steering column.
Have you checked the fuse block under the carpet on the pass side? All power for the cabin goes thru these fuses.
They could be corroded if there was ever water leaking in on the carpet.

Good to know. And no I haven't checked those fuses. The ones by the glovebox were fine but I didn't even know of a fuse box under the carpet. Will check in the am.

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[jicaino]

No need to remove the key lock tumbler to change the electrical switch part. That is on the left side of the steering column.
Have you checked the fuse block under the carpet on the pass side? All power for the cabin goes thru these fuses.
They could be corroded if there was ever water leaking in on the carpet.

Good suggestion about the fuse block. Regarding the lock cylinder, indeed, no need to remove it, but since you're servicing all that, removing it and clean/relube doesn't hurt. I took it out thinking I was going to need to remove it, then realized I took it out for nothing, and tore down the electrical side for replacing the switch. As for innecesary disassemblying I plead guilty as charged, your honor

[JimLev]

As for innecesary disassemblying I plead guilty as charged, your honor

Pick your poison, 40 lashes or a internet text lashing from the Geargrinder, LOL.

[jicaino]

Pick your poison, 40 lashes or a internet text lashing from the Geargrinder, LOL.

[R Shaffner]

Unrelated issue... From the pic I noticed that your strut tower cap is a bit loose. That happened on my car recently, and was a sign that the strut mounts were going bad. Worth a closer look.

[trevzor4242]

Unrelated issue... From the pic I noticed that your strut tower cap is a bit loose. That happened on my car recently, and was a sign that the strut mounts were going bad. Worth a closer look.

Ah that's my bad I was working on them...

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[trevzor4242]

Update: pulled passenger seat and all that nonsense to get a look at the fuses under the carpet - thanks BMW. At first glance it definitely has gotten a bit of water and junk in it, but despite this the connections look fine and aren't corroded at all. As this car is 19 years old and has definitely had the door panels off many times I'm sure the vapor barrier isn't sealing great, however I'm not convinced this is the issue. There's barely any moisture in person and I doubt it affected much. Let me know what you think though. Maybe I should check wiring under the driver's seat too. There's no box but I know there's cables under it.
IMG_20190519_101252472.jpg

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