# BCM Location



## StLouisCPhT (Sep 13, 2015)

Behind the behind the dash/center console, on the floor. Pull off the side panel on either the left or right side of the center console and you'll see it. (I recommend the passenger side panel as that is the side the connectors and hold clips are on.)


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## Blasirl (Mar 31, 2015)

brian v said:


> I guess we will have to search through the pages then for that link for ya .
> There is site to download all of the schematics for this car for free ..
> I might have Gotten the member incorrect .. Maybe Scphi maybe AARCUDA .. 1 of the early members set it up !



Brian, Did you ever locate this?


OP: This is taken from Complete BCM Pin Diagram  and you may want to do the 5 day free thing from Alldata if nothing else. If I can after, work tonight, I will look in my Haynes manual to see if there is a picture.

Edit: I guess I am just a lousy typer and took me too long to answer as you had zero replies when I started.


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## Hockeygirl (Mar 11, 2017)

Thanks. I found it. Just trying to figure out how to pull it out now. Thank you for the quick reply!


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## Hockeygirl (Mar 11, 2017)

StLouisCPhT said:


> Behind the behind the dash/center console, on the floor. Pull off the side panel on either the left or right side of the center console and you'll see it. (I recommend the passenger side panel as that is the side the connectors and hold clips are on.)





Hockeygirl said:


> Thanks. I found it. Just trying to figure out how to pull it out now. Thank you for the quick reply!


. 



Do you recommend disconnecting the battery before cleaning the contacts on the BCM?


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## Blasirl (Mar 31, 2015)

I would. Don,t forget to reset clock and stuff when your done.


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## Hockeygirl (Mar 11, 2017)

No problem, blasirl. I appreciate your help. This car is my 17 year old stepson's car. Given its condition, I expect to need more help in the future, so any info that you can provide is helpful.


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## StLouisCPhT (Sep 13, 2015)

If there is corrosion there, you should check for water leaks also. Some '11s were improperly assembled at the plant and lack a shield over the HVAC air inlet. See this link.


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## Hockeygirl (Mar 11, 2017)

StLouisCPhT said:


> If there is corrosion there, you should check for water leaks also. Some '11s were improperly assembled at the plant and lack a shield over the HVAC air inlet. See this link.



There doesn't appear to be any corrosion (unfortunately?). I'm cleaning all of the pins and connections with QD Electronic Cleaner. It was recommended to me to apply dielectric grease to the pins and connectors. I've read conflicting information on this. What is your opinion on that?


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## StLouisCPhT (Sep 13, 2015)

I've never used the stuff in the 20 years I've worked on my own vehicles so I can't tell you how good or bad it is.

What kind of problems are you having?


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## ChevyGuy (Dec 13, 2014)

Hockeygirl said:


> The car has a lot of odd issues that all seem to tie back to the BCM.


What kind of issues? Are you aware of the Negative Battery Cable issue? That's everyone's "go-to" for strange electrical problems.

And yes, I'd absolutely disconnect the battery before unplugging things.


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## dhpnet (Mar 2, 2014)

Hockeygirl said:


> It was recommended to me to apply dielectric grease to the pins and connectors. I've read conflicting information on this. What is your opinion on that?


No! Dielectric grease is an insulator. It will insulate the terminals so that they don't conduct electricity. 

Most people use it on the spark plug boots to protect against electrical leakage out of the boot, and to make it easier to remove the boot. But don't put it on the electrical connector for the spark plug. 

You can put silicone grease on the battery terminals to protect them from corrosion. When you attach the battery terminal, most of the grease will be squeezed out and it will protect the terminal from gases that are emitted from the battery. Also, the battery has high current, which will pass over the very thin film that is left when you tighten the terminal. 

But, don't put grease on the BCM electrical connectors, unless you don't want them to work.


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## Hockeygirl (Mar 11, 2017)

Well, I cleaned all of the contacts and applied the dielectric grease. I figured it was worth a try since it should help keep out any moisture. I drove it around for a while and everything is working fine. I'm keeping my fingers crossed that the problems don't resume. Thank you both for your help! Have a great day!


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## Hockeygirl (Mar 11, 2017)

dhpnet said:


> Hockeygirl said:
> 
> 
> > It was recommended to me to apply dielectric grease to the pins and connectors. I've read conflicting information on this. What is your opinion on that?
> ...


.

Sorry about that. I just saw this comment. The problems we were having were:

Check engine light on - in trying to resolve the check engine light, I put a new gas cap on, then had an oxygen sensor replaced, but the light came back on soon after

Service Stabilitrak alert was on

RPM's were fluctuating 

There seemed to be reduced power on acceleration

In my research I found that these all can tie back to the BCM. I also found that it seems to be a common problem with some Chevys. Other people have had numerous sensors replaced, only to have the check engine light come back on and show the code for the same sensor that was just replaced. The only solution I've found online is that the problem is with the connections to the BCM. The design of the part encourages moisture and corrosion. Many people have had success with dielectric grease. My thought is that it helps to keep moisture out of the connections. After I cleaned the pins and connectors, I applied a small amount to the surface of each connector, but did not apply it to the pins since, as you said above, it doesn't conduct electricity so I was concerned that it would make the problem worse. So far, all warning lights are out and the car is running great. There isn't the same fluctuation in RPMs that there was and there isn't any decrease in acceleration. I'm going to give it a while before I can confidently say that it took care of all the problems, but it's looking good so far.


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## Hockeygirl (Mar 11, 2017)

ChevyGuy said:


> Hockeygirl said:
> 
> 
> > The car has a lot of odd issues that all seem to tie back to the BCM.
> ...


I had not heard of this issue, but will look into it. Thank you for the information!


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## obermd (Mar 3, 2012)

Hockeygirl said:


> .
> 
> Sorry about that. I just saw this comment. The problems we were having were:
> 
> ...


If the problems return take it to a dealership to have the negative ground cable replaced. What you did was reduce the electrical resistance on the BCM connector. We know the original negative ground cable has a problem with increasing resistance over time.


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## Hockeygirl (Mar 11, 2017)

If the problems return take it to a dealership to have the negative ground cable replaced. What you did was reduce the electrical resistance on the BCM connector. We know the original negative ground cable has a problem with increasing resistance over time.[/QUOTE]

Thank you. I might just do that anyway.


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## dhpnet (Mar 2, 2014)

Hockeygirl said:


> .
> 
> Sorry about that. I just saw this comment. The problems we were having were:
> 
> ...


Adding dielectric grease around the connector housing, while messy, will reduce the chance that you get moisture into the connector. That shouldn't hurt anything. I don't think there is a big risk of moisture getting into those connectors on the Cruze, unless you have a bad seal somewhere or spill water on the dashboard or power wash the carpets. Also, moisture is more likely to enter the connector through the back where the pins are inserted. You would need to find a way to seal that as well. And if there is moisture on the connectors then you have a risk of moisture getting onto the BCM itself because it isn't protected from moisture either. 

As others have stated, your issues sound like the battery ground problem.


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## Blasirl (Mar 31, 2015)

Hockeygirl said:


> There doesn't appear to be any corrosion (unfortunately?). I'm cleaning all of the pins and connections with QD Electronic Cleaner. It was recommended to me to apply dielectric grease to the pins and connectors. I've read conflicting information on this. What is your opinion on that?


Use it!

I'll explain later - at work


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## ChevyGuy (Dec 13, 2014)

dhpnet said:


> No! Dielectric grease is an insulator. It will insulate the terminals so that they don't conduct electricity.


Counter-argument




Hockeygirl said:


> Check engine light on - in trying to resolve the check engine light, I put a new gas cap on, then had an oxygen sensor replaced, but the light came back on soon after
> 
> Service Stabilitrak alert was on
> 
> ...


I'm not sure where you've been reading, but BCM problems on the Cruze are quite rare. The Stabilitrak light tends to come on with most any engine malfunction. So, consider that a red herring. 

What we really need is the codes set. Anything else is just shooting in the dark. But if I was to make a guess, the PCV valve in the valve cover may have died. That's a pretty common fail item. It's also covered by powertrain warranty.


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## Hockeygirl (Mar 11, 2017)

Blasirl said:


> Hockeygirl said:
> 
> 
> > There doesn't appear to be any corrosion (unfortunately?). I'm cleaning all of the pins and connections with QD Electronic Cleaner. It was recommended to me to apply dielectric grease to the pins and connectors. I've read conflicting information on this. What is your opinion on that?
> ...


I did end up using the dielectric grease. I've been driving the car for a couple of days and all of the problems have been eliminated (so far) including one that took me by surprise. Around the same time the other issues started, my stepson said that his remote start quit working. The key fob would still unlock the doors, but wouldn't start the car any longer. I assumed maybe the battery in the key fob was weakening. Just for the heck of it, we tried it after I cleaned the BCM connections and applied the dielectric grease. The car started right up with the remote starter (we did not replace the battery yet). 

I don't know enough about it to understand why this took care of the problems. I dropped the car off at my mechanic's shop tonight. They're going to take a look at it tomorrow, just to make sure there aren't any other issues. I have to admit that I'm surprised that the problems are resolved. I read several forums where others said it worked for them. I figured it was worth a try before taking it in somewhere since it was something that I could easily do at home. I'm keeping my fingers crossed that it will continue to be fine. I'll provide an update after the mechanic looks at it and after it's driven for a few more miles. Thank you everyone for your advice.


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## ChevyGuy (Dec 13, 2014)

Hockeygirl said:


> Around the same time the other issues started, my stepson said that his remote start quit working. The key fob would still unlock the doors, but wouldn't start the car any longer.


If the check engine light is on, the remote start won't work. 




Hockeygirl said:


> we tried it after I cleaned the BCM connections and applied the dielectric grease. The car started right up with the remote starter (we did not replace the battery yet).


If you disconnected the battery, that might have reset the code preventing the car from starting. It also might have cleared up the battery cable issues - for now. If I'm right, they'll be back.


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## Hockeygirl (Mar 11, 2017)

ChevyGuy said:


> Hockeygirl said:
> 
> 
> > Around the same time the other issues started, my stepson said that his remote start quit working. The key fob would still unlock the doors, but wouldn't start the car any longer.
> ...



That's my concern too. After the oxygen sensor was replaced and the check engine light was reset, it took about 50 miles of driving for all of the warning lights to come on again. That's good to know about the check engine light effect on the remote start - thank you. I'll let the mechanic check it out tomorrow, then just keep an eye on it. If the problems resume, I'll schedule an appointment at the Chevy dealer to replace the negative battery cable. Thank you!


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## NickD (Dec 10, 2011)

BCM inputs are near an infinite input impedance and have to be clean, no current rush, like on a 120VAC wall toggle switch that sees quite a surge current to help clean those contact points up.

Last time removing the battery cable cleared codes was in prior 1996 OBD I vehicles, codes were stored in RAM, with OBD II stored in flashram, just like your memory in a digital camera, removing that memory card does not delete your photos, you have to delete them. With automotive, need some type of scanner to do this.

Removing the battery terminal and installing it may make better contact than it had before. These have to be cleaned, battery terminal brushes for this, and here dielectric grease really helps to retard corrosion,also dealing with sulfuric acid fumes that adds corrosion.

So simple to test the battery cables, just switch on the blower full speed, 20 ampere draw and place a digital voltmeter, cheap today directly to the battery terminal, in the case of the negative battery terminal, other lead to an engine point that is ground. Anything above 0 volts is a problem, read 2.1 volts on mine.

Better yet is to have a storage oscilloscope ground at the engine block, hot at a 12V point, have to elevate a fuse with terminals to get an access point. When you hit the starter, the starter and ignition relay contacts close at the same time, starter draws about a 600 ampere surge current until it starts running, if the voltage drops below 8.5 volts, will not get a proper power on reset and the five computers in these things will go crazy.

If all this seems too complicated, can't help it, this is how it is. Also found my ignition relay contacts were dirty and dropping an extra volt.

Another example of what is called a dry contact is the trunk switch, a dry contact is one that does not have any cleaning current that generates an arc. Consequence is that the trunk won't open, but this isn't the only dry contact, practically all of them are this way.


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## Hockeygirl (Mar 11, 2017)

Hockeygirl said:


> Check engine light on - in trying to resolve the check engine light, I put a new gas cap on, then had an oxygen sensor replaced, but the light came back on soon after
> 
> Service Stabilitrak alert was on
> 
> ...


I'm not sure where you've been reading, but BCM problems on the Cruze are quite rare. The Stabilitrak light tends to come on with most any engine malfunction. So, consider that a red herring. 

What we really need is the codes set. Anything else is just shooting in the dark. But if I was to make a guess, the PCV valve in the valve cover may have died. That's a pretty common fail item. It's also covered by powertrain warranty.[/QUOTE]

You are correct! They found a PCV Vacuum leak. Unfortunately, it's no longer under warranty, but it's still a lot cheaper than replacing the Turbo Charger like the other mechanic suggested. Thank you for your help! I felt better about believing them about this issue after reading your comment and researching it a bit.


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