[Chevy_Country]

I just picked my Cruze up from the garage and the mechanic told me that the LED's in my headlights (that I put in after the ecu burnt and kept working even with a bad circuit) and my LED twilight/reverse lights, that were sending codes off in my comouter (obviously) could, and will eventually again burn the ecu out, but I don't know about that, can anyone help with an extra opinion or help me with a fuse relay type protection so i can have a burnt fuse instead of a burnt $450 computer? Thanks!


2011 Chevy Cruze LTZ 1.4L Turbo

 

[ChevyGuy]

I think your mechanic is full of it. Set codes, yes. Damage the BCM - I doubt it.

 

[boneheaddoctor]

Unless. its a poor quality LED with insufficient resistance built into it....a diode WILL suck as much power as you throw at it before it burns up.

 

[NickD]

What are the symptoms, like your engine won't start?

 

[ChevyGuy]

Unless. its a poor quality LED with insufficient resistance built into it....a diode WILL suck as much power as you throw at it before it burns up.

Perhaps. Although I thought the BCM had short circuit protection. And I'd expect a LED to pull less current than a incandescent (until it shorts out).

Just a guess, but I think the codes are likely due to insufficient current fooling the BCM into thinking the light is burnt out. I'd add the resistors to prevent the codes from coming up. Not because it might damage the BCM, but because I don't like having a bunch of codes floating around if I'm trying to troubleshoot some problems.

Nothing like extra garbage confusing the issue - or worse, distracting/misdirecting the mechanic you want fixing some other problem.

 

[boneheaddoctor]

Perhaps. Although I thought the BCM had short circuit protection. And I'd expect a LED to pull less current than a incandescent (until it shorts out).

Just a guess, but I think the codes are likely due to insufficient current fooling the BCM into thinking the light is burnt out. I'd add the resistors to prevent the codes from coming up. Not because it might damage the BCM, but because I don't like having a bunch of codes floating around if I'm trying to troubleshoot some problems.

Nothing like extra garbage confusing the issue - or worse, distracting/misdirecting the mechanic you want fixing some other problem.

It NEEDS far less current to produce light....but its a diode...bias the N-P junctions correctly and its almost a short except for the normal silicon junction voltage drop. That's why you need the resistors on them...to limit current.

As far as the BCM having short circuit protection....yeah that would have been smart to build into it...but someone else will have to confirm if it does or not.

 

[Merc6]

LED headlights? We talking HI/Low beams or the turn signals?

 

[ChevyGuy]

As far as the BCM having short circuit protection....yeah that would have been smart to build into it...but someone else will have to confirm if it does or not.

Well, i sure hope it has protection. Lamps will some times short out when the filament breaks and bounces around.

I'd think the LEDs would fry themselves before the ECM goes. LEDs have no tolerance for massive overload.

 

[NickD]

LED is a diode, called a light emitting diode, compared to a conventional diode with a typical forward drop of around 0.6 volts, rather high at 1.8 volts, they do get hot. If connected in reverse, have a breakdown voltage that will burn them out. Some conventional diodes can hand a reverse voltage of 10,000 volts without failure, and LED can only handle about 3 volts, creates a so-called avalanche current that will destroy it. Have to observe polarity with these things.

A USA invention that came out in the late 60's, at first we used them to replace incandescent lamps,then seven segment displays came out shortly after to replace Nixies that required 200 volts to operate, these could run off of five volts. Still have equipment from back then, still working fine some 45 years later. Wife wanted LED Christmas lights made in China, we thought our problems would be over, our problems just started, 30 or so in series, when one burns out, they all go out, have to check each one, one at a time. Merry Christmas from China. Impurities in the intrinsic silicone is the major problem as well as soldering the cathode to a decent heat sink, just a piece of tin. Anodes are ultrasonically welded aluminum wire.

They made seem cool, but those chips are tiny with a rather high heat density. Took one apart, chip has to be metalized, very poor job.

Already posted a circuit diagram of the head lamps circuits, brights are simple, point contact relay fired by the BCM, to two fuse to each high beam filament to ground. A fuse should burn out with a short, BCD is isolated by that relay.

Dims are fired by the BCM, either a chopped waveform for DRL or a solid 12 V for lighting, also each filament has a fuse. ECU has nothing to do with the lights except to tell the BCM the engine is running to switch on the DRL's. Parking brake when engaged with a real switch, tells the BCM to switch off the DRL's, but no effect with the head lamps. Typical LED's use a ballast resistor to limit the current, typically only five can be added in series, need parallel strings to get more for 12V. Should be a resistor for each string, unless they tried to get by with one, a bad mistake. All the LED's have to be perfectly matched. Can be tested with a 12 volt power supply.

Now for the key question, what happens when you replace these with the original bulbs?

 

[NickD]

Regarding mechanics and electronics, have yet to meet any with any kind of electronic training, here is the latest example.

A good friend with a WV Golf cruise control quit working, took it to his VW dealer, said they checked everything and the problem has got to be the ECU, wanted 1,300 bucks to replace it, already charged him 450 bucks for diagnostics.

First question I had, does your speedometer work and does your AT shift right, said yes. Was told some kind of signal is missing, so can't be the Vss. Neck question, what about your gas pedal, does that work okay, does have throttle by wire, and the same exact output is used by the cruise. Only difference is that throttle voltage is converted into digital and stored into RAM, by command from the cruise switch, interrupted by the brake switch. Also by the cruise switch with on-off and a button, but still need continuity from the brake switch. They said they checked all this, but how?

So I found him a used ECU from a cruise working vehicle for 150 bucks, took it to his dealer charged him another 200 bucks, if you are keeping track, 800 bucks already, and the cruise is still not working. So now saying must be a wire someplace, but they claimed they already checked it. Told my friend to bring his car over, let me look at it.

With all this new BCM crap, can't think of a better word, the switch contacts have to be perfect, Cruze trunk switch is a good example of this, its a dry circuit? Meaning no arcing current flows. Also a point contact, doesn't take anything to corrupt these switches. Cruise is even more finicky, has fixed resistors that send different voltages to the ECU, if slightly off, nothing works. Even doing a net search on this problem cruise control switch was the major problem, only a few had brake switch problems.

But dealing with mechanics that have zero electronic training.

Ha, when I got into my old motorhome that used a memory solenoid with an arcing current didn't work after sitting all winter long. Worked that slide switch several times, then worked fine all summer long, self cleaning contacts and an arc current. You don't have this luxury with a BCM. Everything has to be perfect.

Should be getting in my new ignition relays in today or tomorrow, can't wait to compare these with the piece of crap that came with my Cruze. Just more problems.

 

[Merc6]

...Now for the key question, what happens when you replace these with the original bulbs?...

Yeah, after reading I wonder what all was converted for LED headlights and if they could simply go back easily.

 

[Chevy_Country]

makes perfect sense ill look into the resistors! thanks!

 

[Chevy_Country]

LED headlights? We talking HI/Low beams or the turn signals?

I have LED HiI/Lo beams, but5 my computer burnt out 4 months ago and i just got around to having it fixed and i had HID's in when it burnt and the HID's worked just fine before and after the computer burnt out and i switched to LED's with a bad computer and haven thad an issue, I had accidentally crossed the ground with the feed on my sub's amplifier wiring and i'm 99% sure thats what fried the BCM but there was a fuse on that circuit, i think that did it because i noticed bad blinkers loss of map/vanity/glove box lights after that pop lol but everthing i have LED worked fine before the computer burnt and after as well