# Electrical problem



## will67 (Oct 20, 2015)

I have a 2011 Cruze with a re-occurring electrical problem. Rear brake lights, windshield washer, trunk release stopped working. found the problem to be the Body Control Module. Bought one and brought to the dealer to be programmed to the car. Everything was fine for a week. Then, the problems returned with the addition of the tail lights not working. What could be killing the module? something else all together?
thanks


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## obermd (Mar 3, 2012)

Has your negative battery cable been replaced yet? I ask because under voltage (brownout) conditions can damage electronics. The negative battery cable failure causes this type of condition.


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## ChevyGuy (Dec 13, 2014)

Have the fuses been checked? I'm not near my manual, but some of those things may be on the same fuse.


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## will67 (Oct 20, 2015)

I have checked all fuses with an ohm meter. All were good.


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## will67 (Oct 20, 2015)

it has not been replaced. was this on a recall do you know? The dealer did 3 recalls when they programmed the BCM. Could not determine what they were from the paperwork


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## ChevyGuy (Dec 13, 2014)

will67 said:


> it has not been replaced. was this on a recall do you know? The dealer did 3 recalls when they programmed the BCM. Could not determine what they were from the paperwork


You can read the details of the battery cable here: Special Coverage #14311: Negative Battery Cable.

However, it doesn't seem to describe your problem. I would not expect the BCM to be damaged unless the charging voltage went sky-high or the cable opened up entirely removing all filtering.


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## NickD (Dec 10, 2011)

When a BCM fails, nothing works, not even diagnostic codes. But take a look at all those point contact relays in the underhood fuse relay box. Owners manual and whats listed under that cover panel only shows the top board. They completely forgot about that board underneath that top board with even more point contact relays on it. 

For experienced engineers, the point contact relay is the poorest choice, any surge currents caused by incandescent bulbs or inductive loads will generate a spark where the slightest amount of debris prevents good contact. When we had brains, would use a self cleaning sliding contact. Also the materials, silver alloy was a very bad choice, has a very low melting point, tungsten is far superior, but due to the higher resistivity, larger contacts have to be used. 

See GM has a special tool to pull out these relays, must have weak fingers, and if you squeeze to hard will break that weak plastic case. Okay, I am getting old, have to use both index and thumb on both hand to pull it straight up. Can't wiggle them, will spread the female terminals underneath that will cause poor contacts, has to be tight. 

When my radio started flashing on and off, first placed I checked, of all things was the ignition relay, what tiny little contacts this relay has for the major loads its expected to handle. Cleaned the contacts, but did order a superior relay for this most important switch.

There are means to test contacts, I use a constant current source, up to 30 amps, energize the relay, and measure the voltage drop across the contacts, anything about 0.1 volts is not good. Also be constantly energizing the relay, can check for repeatability. Each closure will be different. 

See practically all new cars are going this route, not a good idea, very easy to lose your head lamps. Suppose after several people get killed, they will go back to the good old fashion way,.

In terms of microprocessors have to have a very clean voltage, only thing that filters this is the battery, have to have good clean and tight connections. Caught this practically instantly with my brand new Cruze, first I wanted to use dielectric grease to retard corrosion. And in particular with all those connection on the positive side of the battery. Told myself, this is dumb, age old problem with any wiring close to the battery, also some acid present. 

Was shocked to find even though the negative battery bolt was tight, the terminal was still loose, so removed it and filed in between the clamps so a gap would be in there.

This is a before photo, ha, my hands were dirty for the after photo.

View attachment 167466


An after photo of my negative battery terminal, this is how it should look like.

View attachment 167474


Never blame engineers for problems like this, for about 60 cents extra, could design a linear voltage regulator that applies field voltage in proportion to alternator load and speed. But marketing won't hear of it, so using a cheap on off switch transistor that pulses 400 times per second, each time generates a transient, but the battery has to filter this out.

And if you don't do it their way, will find somebody else that will.

Gee, it only took GM three years to discover they had a battery terminal that was too loose!

Getting rid of the radiator cap and a purge valve in the cooling system always leaves air in the system. Caught this three days later with low coolant. Also only took them three years to discover this. Have bottle of Dex-cool, topped it off on day three.


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## ChevyGuy (Dec 13, 2014)

will67 said:


> I have checked all fuses with an ohm meter. All were good.


I assume you know there's two fuse panels - one under the hood and one by the driver's left knee.

I don't see any relays involved with the lights - just the battery saver relay.

Any modifications to the electrical system? Added devices? 

If it was me, I'd be looking for loose connectors on the BCM.


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## NickD (Dec 10, 2011)

Which BCM connector would that be, there is seven of them, why do they have to make these things so complicated?

Check the lights on my old motorhome, right front parking and directional signal was working. That sure would get me a ticket, search of my motorhome, and possibly even getting seven bullets in me. First click of the dash mounted light switch is all they used, applies 12 V to the parking light, two screws removed it, socket made of poor sheet mile was a pile of rust, use to use plated brass that didn't rust, wasn't even plated. Had to spend five bucks for a new socket, checked the other three while I was at it.

Never discovered only one of my two backup lights on my Cruze wasn't working, no more bayonet bulbs, these poor ones with the wire tabs on it. And the only way the backup lights turn on, is with the engine running and gear shift in reverse, not easy with an MT. 

Since I was working alone as I usually am, had to jack up one of the front wheels, parking brake on, rear wheels block, in reverse with the engine running so I could make voltage checks. This was the left one, with a volt meter saw two tiny tabs in the back light socket. Already tested that the bulb was good. But learned only two of the tabs inside that socket was hot, other side was dead, and that was the side that was so suppose to make contact with that cheap wire tab on the bulb.

I bend that one tab the other way, then the bulb lite up. Complained about this to my rotten idiot dealer in that short harness was wire wrong, and how come both tabs aren't hot. That AH refused to give me a new one as long as reversing the tab on the bulb worked. Hate that idiot. So if that bulb burns out, have to remember to reverse that tab. 

Pins 5 and 6 on X4 connector are the right and left side parking light control. Don't know why there is two, they all come on at the same time. And since it is a control, can only assume this fires a relay, someplace. As I mentioned, can't find any data on that lower relay board in the underhood fuse/relay box. Could be in the shop manual, give me another ten years to find it. This is the worse possible shop manual I ever purchased. Who ever came out with this should be shot. 

This is all I can find for the parking lamps.










Worthless, if you go to your dealer like my idiot, tells me to trade it in for a new one. If you have this problem, so can the rest of us.


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## Ghost14 (Jan 25, 2019)

will67 said:


> I have a 2011 Cruze with a re-occurring electrical problem. Rear brake lights, windshield washer, trunk release stopped working. found the problem to be the Body Control Module. Bought one and brought to the dealer to be programmed to the car. Everything was fine for a week. Then, the problems returned with the addition of the tail lights not working. What could be killing the module? something else all together?
> thanks


Having same issues. Did you buy new BCM or from somewhere else? If that happens to be an issue it would really hurt me financially at the moment.


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## lasse (Mar 28, 2021)

Im facing some electrical issues, and im wondering if someone can please help ? gettin desperate here 
the issue seems to look like a bad charge of the battery, cause sometimes i face starting issues, like i need to turn the key a few times before starting . just changed the starter, and also the negative battery cable , cause the whole car was acting up, and in the end just died while driving . besides starting issues , the stereo have lost all lights, funktions and sound. the upper part still works... both touch and nav. i tried changing the positive battery cable and also the radio fuse. please help


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## lasse (Mar 28, 2021)

and the car only has 105.000 km i dont know what that is in miles. 40.000/50.000 miles ?


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