NA - BMW electrical gremlin diagnosis

MAKG1

Touchdown! Greaser!
Joined
Jun 19, 2012
Messages
13,411
Location
California central coast
Display Name

Display name:
MAKG
OK, the BMW is developing some interesting electrical behaviors, and I'm having some trouble finding the source(s). It's a 2000 323i (e46) sedan with a stick and "base" ("business CD") radio with no CD changer nor amplifier in the trunk. It seems to be something in back, but everything I can find makes no difference.

1. Backup lights inop. Bulbs are good.
2. Rear defogger inop. I can measure a good voltage drop across the grid, but it doesn't evaporate anything and doesn't get warm. The relay light does turn on.
3. Poor radio reception. Doesn't matter if the rear defogger is on or not. If I disconnect the antenna feeds from the diversity module, all reception goes away entirely. All electrical connections to the rear glass look really good.
4. Headlights intermittently drop out for a split second.
5. Right rear and right front lights-out indication trips intermittently and then goes away with no intervention.

There are no discernable drivability issues and the check engine light is not on. I haven't checked for pending codes. Cranking is normal, so it isn't a dead body ground (there is no separate engine block ground to the battery in this vehicle -- it ALL goes through the body). I can find no substantial corrosion anywhere on the vehicle.

I've taken both the C pillars off to clean grounds for the diversity module and wave trap (using electrical contact cleaner). I've cleaned the battery ground (in the trunk). What I haven't done is check out the alternator and engine block ground, as I'm now starting to suspect I have a voltage regulation problem.

Any pointers from someone more familiar with these very complex electrical systems than I am?
 
Drive it off a cliff and buy an Audi.

Having dealt with VW electrical systems before, you gotta be kidding me.

At least the BMW has MINOR problems. The VW/Audi just quit with no notice as it ate its Hall sensor or blew a coil (repeatedly).
 
OK, guys, let's be clear.

I'm not going to unload a car for an electrical gremlin. Period.

Just like you aren't going to throw away an airworthy airplane just because a tire goes flat. You fix it.
 
Drive it off the cliff and buy a Toyota! :).. Honestly, don't know, but BMW and electrical gremlins... What a cliché ? (and yes I've had those)
 
Usually I've found the make-specific auto forums to be of great help with these types of things, especially if it's a common issue. German cars seem to have a lot of common issues.
 
Drive it off the cliff and buy a Toyota! :).. Honestly, don't know, but BMW and electrical gremlins... What a cliché ? (and yes I've had those)
My other car is a Toyota. One if these days it's going to drive itself off a cliff. The steering and suspension is TERRIBLE. Much too soft.
 
My other car is a Toyota. One if these days it's going to drive itself off a cliff. The steering and suspension is TERRIBLE. Much too soft.

At least it will make it to the cliff :)
 
I second copying your post over to a BMW-specific forum.

Don't worry. My A4 had both electrical and mechanical issues. On some cold mornings, the entire instrument cluster would go out and all of my needles would move to their "off" position as if the car had just been shutoff. It'd come back after a few seconds but I enjoyed guessing my speed.
 
Hate to say it but the diagnosis is contained within the thread title.
 
*sigh* You guys.
How about trying to help a little?
From my past experience with automotive wiring, you could be looking at a few bad connections and bad grounds. You are in California so I wonder how much the salt air affects electrical systems there (vs let's say NY with snow and road salt).
You need to get a manual with electrical diagrams and follow the circuits to determine where the fault is. Otherwise we all are just guessing.
If you have some online diagrams, feel free to PM me for more detailed help.
 
OK, guys, let's be clear.

I'm not going to unload a car for an electrical gremlin. Period.

Just like you aren't going to throw away an airworthy airplane just because a tire goes flat. You fix it.

Stay tuned folks. Film at eleven.
 
I've got a service manual, and I'm aware that these electrical problems are often very easy to fix once found.

The BMW electrical diagrams SUCK. Looks like UML. No connectors, few wire colors (not surprisingly, coded in German -- SW = black), spotty cross-referencing. And I only have them on paper.

The electrical system is put together like a fighter aircraft. It's largely digital, and has three independent networks (which it calls "busses"). Several dozen modules. And the usual trace-the-circuit-until-you-find-the-voltage-drop trick is not working.

I don't have nearly this much trouble diagnosing a Ford truck with its measly three computers (EEC, ABS and TFI). This thing has many dozens; just about everything has some module/controller communicating over the CAN. Even things like the wipers, fog lights, etc.

I'm strongly suspecting a problem with grounds or power supply.

Per the earlier suggestion, I've posted the same question on bimmerforums.com. No response yet; we'll see.

I have run across a recall for a slightly later e46 for the intermittent lights-out problem. It seems the ground wires in the taillights burn (very slowly), leading to intermittent poor connections. My year is not covered, but I'll take a look when I get home. It also appears that the headlight flicker is a sign of a slowly dying alternator. I believe they are xenon, and have a relatively high activation energy.
 
Last edited:
if it isnt a bad wire (cut, etc) or a ground, look at common modules. Figuring out stuff over CAN is a pain. Check what you can then find some guy named Klaus to fix it. If you were in SoCal i could give you a couple names.
 
OK, the BMW is developing some interesting electrical behaviors, and I'm having some trouble finding the source(s). It's a 2000 323i (e46) sedan with a stick and "base" ("business CD") radio with no CD changer nor amplifier in the trunk. It seems to be something in back, but everything I can find makes no difference.

1. Backup lights inop. Bulbs are good.
2. Rear defogger inop. I can measure a good voltage drop across the grid, but it doesn't evaporate anything and doesn't get warm. The relay light does turn on.
3. Poor radio reception. Doesn't matter if the rear defogger is on or not. If I disconnect the antenna feeds from the diversity module, all reception goes away entirely. All electrical connections to the rear glass look really good.
4. Headlights intermittently drop out for a split second.
5. Right rear and right front lights-out indication trips intermittently and then goes away with no intervention.

There are no discernable drivability issues and the check engine light is not on. I haven't checked for pending codes. Cranking is normal, so it isn't a dead body ground (there is no separate engine block ground to the battery in this vehicle -- it ALL goes through the body). I can find no substantial corrosion anywhere on the vehicle.

I've taken both the C pillars off to clean grounds for the diversity module and wave trap (using electrical contact cleaner). I've cleaned the battery ground (in the trunk). What I haven't done is check out the alternator and engine block ground, as I'm now starting to suspect I have a voltage regulation problem.

Any pointers from someone more familiar with these very complex electrical systems than I am?

While not impossible, I'd doubt some of these issues are inter-related. It's not impossible that they would be, as some vehicles utilize a body-control module that everything seems to run through and it can play crazy games with electronics that would normally not affect one another outside of a shared ground.Edit: I see that you are aware of the BMW - CAN system, so at least you understand how frustrating it can be.

1. Have you tested the other items that activate when in reverse (reverse sensors and/or auto down-mirrors)? If those don't work, I'd suspect the reverse switch on the transmission itself is kaput.
2/3. Defogger/radio could be inter-related, I'd inspect the grid for any breaks in the defroster that might be interfering with the radio antenna. Tint shops are notorious for cutting them with a razor while installing tint.
4/5. Headlights dropping out/right side lights out indications sounds like a relay or connection/ground issue. Have you pulled the fuses and relays related to the headlight/running light circuits to make sure they are all solid and no broken pins?
 
While not impossible, I'd doubt some of these issues are inter-related. It's not impossible that they would be, as some vehicles utilize a body-control module that everything seems to run through and it can play crazy games with electronics that would normally not affect one another outside of a shared ground.Edit: I see that you are aware of the BMW - CAN system, so at least you understand how frustrating it can be.

1. Have you tested the other items that activate when in reverse (reverse sensors and/or auto down-mirrors)? If those don't work, I'd suspect the reverse switch on the transmission itself is kaput.
2/3. Defogger/radio could be inter-related, I'd inspect the grid for any breaks in the defroster that might be interfering with the radio antenna. Tint shops are notorious for cutting them with a razor while installing tint.
4/5. Headlights dropping out/right side lights out indications sounds like a relay or connection/ground issue. Have you pulled the fuses and relays related to the headlight/running light circuits to make sure they are all solid and no broken pins?

Thanks. Good stuff here.

1. I'm not aware of anything else that triggers in reverse. But maybe that means the answer is that they don't work.
2/3. I've probed the back glass for voltage drops, and I'd expect I'd find a break if one were there that way.
4/5. I haven't looked at those specific fuses and relays, yet.
 
I had a 2003 330i with electronic gremlins. After the 5th time in the shop, I asked BMW Corp for a new car. They told me **** off.

I sued them and got almost every last penny minus gas put of them.

I went and bought a Lexus IS350 and drove it into the dirt and it never whimpered once. Lexi didn't have that rock solid feel like the Bimmer, but what she lacked in handling she made up for in brute power.

And she never once asked to go into the shop in 112k miles.
 
OK, the BMW is developing some interesting electrical behaviors, and I'm having some trouble finding the source(s). It's a 2000 323i (e46) sedan with a stick and "base" ("business CD") radio with no CD changer nor amplifier in the trunk. It seems to be something in back, but everything I can find makes no difference.

1. Backup lights inop. Bulbs are good.
2. Rear defogger inop. I can measure a good voltage drop across the grid, but it doesn't evaporate anything and doesn't get warm. The relay light does turn on.
3. Poor radio reception. Doesn't matter if the rear defogger is on or not. If I disconnect the antenna feeds from the diversity module, all reception goes away entirely. All electrical connections to the rear glass look really good.
4. Headlights intermittently drop out for a split second.
5. Right rear and right front lights-out indication trips intermittently and then goes away with no intervention.

There are no discernable drivability issues and the check engine light is not on. I haven't checked for pending codes. Cranking is normal, so it isn't a dead body ground (there is no separate engine block ground to the battery in this vehicle -- it ALL goes through the body). I can find no substantial corrosion anywhere on the vehicle.

I've taken both the C pillars off to clean grounds for the diversity module and wave trap (using electrical contact cleaner). I've cleaned the battery ground (in the trunk). What I haven't done is check out the alternator and engine block ground, as I'm now starting to suspect I have a voltage regulation problem.

Any pointers from someone more familiar with these very complex electrical systems than I am?
Sounds like a Jeep Cherokee... good luck.
 
I had a 2003 330i with electronic gremlins. After the 5th time in the shop, I asked BMW Corp for a new car. They told me **** off.

I sued them and got almost every last penny minus gas put of them.

I went and bought a Lexus IS350 and drove it into the dirt and it never whimpered once. Lexi didn't have that rock solid feel like the Bimmer, but what she lacked in handling she made up for in brute power.

And she never once asked to go into the shop in 112k miles.
My grandparents have had various Lexus' as long as I have known them (lol) and I haven't heard one single complaint towards the brand. They've been nothing but reliable. My mom has also had an Infiniti Q37S for almost 5 years now and has not had one major issue. I know those two companies will be what I'm heading towards when the time comes.
 
Thing is, there's definitely a difference in the nature of the driving experience between a BMW and your average Japanese vehicle. I've been a Honda (Acura) fan for a long, long time, and I have no doubt they're far more reliable than their German counterparts. But I also get something from driving the BMW that just doesn't exist from Acura. Whether that's worth the extra money to maintain the damned thing, I still haven't quite figured out.
 
Im no help for thread but, a question...is there an American made automobile that's worth driving?
It's
-> Pilots of America??
Not pilots of Japan, our whichever country owns them there,other vehicles

I must be missing something :)
 
This thing has many dozens; just about everything has some module/controller communicating over the CAN. Even things like the wipers, fog lights, etc.

Do you have a CAN-bus sniffer?

It also appears that the headlight flicker is a sign of a slowly dying alternator. I believe they are xenon, and have a relatively high activation energy.

If it is the alternator then you should be able to see that on a voltmeter or oscilloscope.

But I also get something from driving the BMW that just doesn't exist from Acura. Whether that's worth the extra money to maintain the damned thing, I still haven't quite figured out.

Not long after Soichiro Honda died Acura slowly watered itself down, I think. You ought to try a modern Mazda. Hopefully they'll put the turbo CX9 motor in the 6 and/or 3 someday.

Im no help for thread but, a question...is there an American made automobile that's worth driving?
It's
-> Pilots of America??
Not pilots of Japan, our whichever country owns them there,other vehicles

Depends on the mission. :)
 
First and foremost, to the OP, look aggressively for bad grounds. German cars (and yes, some Japanese ones, too) are notorious for poorly-engineered ground connections, most notably at the tail-lights. Tail lamp modules are usually those big, honkin' plastic modules with steel or aluminum conductors modeled in. They usually rely upon a tab of sorts, or a conductor in the multi-pin connector, for the ground, and since the ground carries all the current fed in by all of the various light feeds (tail, turn, brake, backup), the contacts get hot and build resistance, which makes them hotter, and more resistance, and pretty soon, no more ground.

At that point, you're getting all manner of gremlins, as voltage is back-fed through the light bulb filaments. Seriously. Spike says, "check it out." I had to fix this issue on one Audi, a VW and two BMWs.

Im no help for thread but, a question...is there an American made automobile that's worth driving?
It's
-> Pilots of America??
Not pilots of Japan, our whichever country owns them there,other vehicles

I must be missing something :)

Lots of remarkably good American cars. For high-performance, try the Cadillac CTS or ATS, great drivers, tough as nails. The Ford line includes a Fusion, which is simply stunning (esp for the $$), and the current Taurus is a very comfy big car.

The American car I am Jonesing after is the Chevrolet SS sedan, good styling, big Corvette V8, choice of auto or Manual, handles like a car twice as costly. Of course, this particular American car is built in Australia - for one more year.
 
Im no help for thread but, a question...is there an American made automobile that's worth driving?
It's
-> Pilots of America??
Not pilots of Japan, our whichever country owns them there,other vehicles

I must be missing something :)
What's an American made car?

GMs are assembled in Mexico. Toyotas and several others in the US.
 
....My mom has also had an Infiniti Q37S for almost 5 years now and has not had one major issue. I know those two companies will be what I'm heading towards when the time comes.

I have a low mileage 2006 Infiniti G35x that has been stunningly reliable. The only exception is it had two battery failures in the first five years. It is now a member of the family it seems.... And it packs a very decent punch under the hood!

-Skip
 
Lots of remarkably good American cars. For high-performance, try the Cadillac CTS or ATS, great drivers, tough as nails. The Ford line includes a Fusion, which is simply stunning (esp for the $$), and the current Taurus is a very comfy big car.

The American car I am Jonesing after is the Chevrolet SS sedan, good styling, big Corvette V8, choice of auto or Manual, handles like a car twice as costly. Of course, this particular American car is built in Australia - for one more year.

Hell, the Taurus SHO will run pretty hard and has a ton of tech features to do it in style. It gets mixed reviews on interior/exterior styling, but I don't find them terrible. The Chevy SS is a great car, but, as with everything else Chevy (sans 'Vette) they made it as boring as could be on the exterior. It's akin to what they (GM) did to the GTO. As for others, the Ford Mustang GT still has the highest power-to-weight ratio of anything sub-$40K I think. I've only driven a few BMWs (528i, X3, old M3) and I can honestly say I wan't particularly impressed except for the old M3. The fit and finish didn't seem to be anything extraordinary, and performance wasn't anything to write home about either. They do handle well and ride quiet/smooth, but I feel like you have to have the M-series or large engines in order to get any "well-roundedness" to them, and at that point you're talking major $'s. I haven't met too many people with the Bimmers who didn't have all manner of electrical gremlins, regardless of vehicle model or age. It's just synonymous with owning one. That being said, to each their own. I always liked the appearance of the 90's/early '00 3/5-series, just could bring myself to depend on one for daily transportation!
 
Well, it looks like my hunch has some truth to it. The BMW is no longer charging at idle. For the moment, it's OK at cruise, but I don't believe it's properly rectified. Lots of drift in regulation as well.
 
Well, it looks like my hunch has some truth to it. The BMW is no longer charging at idle. For the moment, it's OK at cruise, but I don't believe it's properly rectified. Lots of drift in regulation as well.

"rectified" as in diode action (electrical jargon)? Or "rectified" as in corrected/repaired (colloquial English)?
 
I'd wager a bad ground somewhere, a bad relay somewhere, or possibly fuze trouble (least likely). Have you been over to bimmerforums or e46fanatics? Both would have much better advice than the consensus over here, which seems to be "drive it off a cliff". I own an M3 built in west germany, and another that is much newer…….have had little to no significant problems with either, save some electrical gremlins like you are experiencing. They are great cars, don't get me started on the cheap ergonomic nightmare that is any japanese market vehicle.
 
At that point, you're getting all manner of gremlins, as voltage is back-fed through the light bulb filaments. Seriously. Spike says, "check it out." I had to fix this issue on one Audi, a VW and two BMWs.

I've had 2 VW, 3 Benz, and one BMW, and this is what chaps me about German cars and why I'm now done with them. Yeah, they drive great, but for $60k/car why can't they figure out simple stuff (like tail light grounds) when Honda et al can on a Civic/basic car for $15k?

We had a 2006 E class Benz, it was a decent car, replaced it with a new Fusion 2.0 Ecoboost with all the toys. We don't miss the Benz a bit. The Fusion is just as smooth, quiet, and refined, and out handles the Benz. The Fusion has all the toys the MB had and more. I still love my old F-150, and we're loving the Fusion. I'm back to all American, baby! As good as common cars have gotten, the only real reason to own a BMW/MB/Lexus, etc., is for the badge/snob appeal.
 
I've had 2 VW, 3 Benz, and one BMW, and this is what chaps me about German cars and why I'm now done with them. Yeah, they drive great, but for $60k/car why can't they figure out simple stuff (like tail light grounds) when Honda et al can on a Civic/basic car for $15k?

We had a 2006 E class Benz, it was a decent car, replaced it with a new Fusion 2.0 Ecoboost with all the toys. We don't miss the Benz a bit. The Fusion is just as smooth, quiet, and refined, and out handles the Benz. The Fusion has all the toys the MB had and more. I still love my old F-150, and we're loving the Fusion. I'm back to all American, baby! As good as common cars have gotten, the only real reason to own a BMW/MB/Lexus, etc., is for the badge/snob appeal.

I honestly think a large part of BMW (and sometimes Mercedes) problem is OVER-engineering stuff. They are usually the some the first to have new tech (auto cruise control, auto braking, auto-fold mirrors, etc) and they make everything so interconnected that one problem often causes a lot of others. I won't begin to say that a Fusion out-handles a BMW, but I guess it depends on the comparison vehicle in BMW's lineup. I like the Fushion/MKZ as well, but I'm not sure sporty handling is its strong suit (technology and use of space is). The M3 (originally) was an absolute monster that could be daily driven and had next to nothing that could compete with it in the same vehicle class. Nowadays, there is much more parity between vehicles that, unless you are spending $70K+, there's not enough value in buying a 1 through 5-series. I think the lower-tier auto makers have gained enough ground on tech/luxury features (and performance) since the early-'00s that it makes less sense to buy the Bimmer/Mercs.
 
Electrical noise coming off a failing alternator can offten triger the modules on the bus to switch off. My wife's 2008 Durango had a string of odd failures that fixed themselves after replacement of the alternator. The heated seats failed to work, side view mirrors would no longer tilt down in reverse etc. Good Luck!
 
Electrical noise coming off a failing alternator can offten triger the modules on the bus to switch off. My wife's 2008 Durango had a string of odd failures that fixed themselves after replacement of the alternator. The heated seats failed to work, side view mirrors would no longer tilt down in reverse etc. Good Luck!
That is EXACTLY what I was thinking, and why the alternator is getting fixed first.

I have enough experience with digital circuits to know all kinds of bad things happen with poor power conditioning.
 
We had a 2006 E class Benz, it was a decent car, replaced it with a new Fusion 2.0 Ecoboost with all the toys. We don't miss the Benz a bit. The Fusion is just as smooth, quiet, and refined, and out handles the Benz. The Fusion has all the toys the MB had and more. I still love my old F-150, and we're loving the Fusion. I'm back to all American, baby! As good as common cars have gotten, the only real reason to own a BMW/MB/Lexus, etc., is for the badge/snob appeal.

Ford's refinement is beautifully displayed in the Fusion, which is a perfect size, tight, well-crafted and rock-solid. I love 'em.
 
Back
Top