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RPM's jumping up

33K views 9 replies 5 participants last post by  WearTheFoxHat 
#1 ·
Hi my name is Charlene,
I have a 2009 Chev. Malibu with 107000 miles. Recently the rpm's have been jumping up on it without accerleration. My rear window brake light has also been acting crazy, it will stay on when I am not braking. That I am not so concerned about. The rpm's is concerning. Anyone see this problem in the Malibu's and how was it solved? I hate to take it in without knowing a possible cause and spend a fortune. Would like to know what I may be facing cost wise. Thanks for your help.
 
#2 ·
The brake light problem is most likely a terminal connection issue at the BCM. There is a bulletin from GM regarding such issues. When you say the RPM's jump up. How much of a jump are you talking about? A hundred or so RPM or more? When did this problem start, has it been getting progressively worse?
 
#5 ·
Charlene, did you ever find out what was happening with your vehicle? If so what was the resolution? I have a 2009 Chevrolet Malibu LT with just over 100,000 miles and it is doing the exact same thing. At an idle speed (say 70 mph it'll jump from 2k to 3k RPM as if stuck in a gear) at the same point where it was doing that my 3rd break light (rear window) would stay on even when not breaking, some of my power locks wouldn't always shut off and my cruise control no longer will function. I found it odd that all these things that seemingly didn't go hand in hand started to occur for the past few weeks all around the same time.
 
#6 ·
Though it may seem otherwise, these issues are well known & probably unconnected.

You probably have the tach jumping issue which I don't think we really have an answer for yet.

You probably have the infamous brake lamp issue which disables the cruise control. Already covered in many threads. Easy DIY fix.

You probably have the failing door locks issue. Also covered many times already. A motivated DIYer can replace these or a dealer charges around $250 per door.

I would start by fixing the brake lamps as that is very dangerous having the lamps work the opposite of the way they should.
 
#7 ·
I believe that the brake light issue and the RPM issue are related. I too have the brake light problem and am currently seeking for the fix (that's why I'm here :) ). Anyway, one thing I noticed is the RPM's will only jump-up when the brake lights are on, and usually at highway speed. It's actually become my indication of when my brake lights are on while driving in daylight hours. I'm going to get the lights fixed and hope the RPM thing takes care of itself.
 
#8 ·
You are the first person that I can recall associating the two issues but what I can tell you is the brake pedal position sensor signal is analog while the tach signal is carried on the GMLAN bus (i.e.-it's digital data). There's a pretty good consensus on what causes the stop lamp issue (corrosion build-up at the BCM terminal increasing circuit resistance) but the tach needle-jumping issue is still a mystery (at least to me).
 
#9 ·
In my situation, the cause of RPM's being high is more of a transmission thing, not a tach error or sudden increase of engine speed. What happens is the transmission will not shift into a higher gear. I have a LTZ so when this happens I shift the stick to "manual" mode and use the steering wheel paddles to shift into 6th gear. Like I said before, this is how I know my brake lights are on. It will not do it any other time- hands down.

I've had my car for a few years now and it's been nothing but an ongoing electrical nightmare. There's no doubt in my mind that these two things are related. How or why? I have no idea.

I read about the BCM/tail light fix and will try it tonight. It will be interesting to see if the RPM/tranny thing disappears.
 
#10 ·
Just wanted to give a quick update: I did the BCM fix as described on other threads (and there's also a Youtube video of the same fix done to a Pontiac G6). Since the 19th I've put 590 miles on the car, which most of those miles are highway. Not once have I had my tail lights automatically come back on, nor has the transmission been shifting irregularly to cause high RPM's. I truly believe I've "killed two birds with one stone" and hopefully this is the end to my ongoing problems.

My advise- if your tranny is shifting oddly, do the BCM dielectric grease fix. You may be surprised.
 
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