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12 Second Club
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672 Posts
Discussion Starter #1
The dealer found a short in the bcm, they replaced it. Now my MPG went from avg of 24-25 to 19. Not sure what the BCM really does. No matter how i drive it, it will not go over 19.6.

I did install the LPE CAI when i got it back. Should that kill the MPG'S?

Any of the braintrust here heard of anything like this? Any Ideas?

Thanks!
 

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Blue Thunder
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821 Posts
Could be that the short in the old BCM was causing an incorrect reading of the MPG? I know mine dosnt go over 19 ever. I would think that the CAI wouldnt hurt MPG because it is more efficient.

-Brian
 

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12 Second Club
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672 Posts
Discussion Starter #3
Thanks for the post. I had been double checking the MPG manually and checking it against the computer. It was accurate to about a half gallon per tank. I was actually getting the 24-25 manually figuring it. And yes i was driving it like a granny to get that MPG.
 

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That's Got A V6 Right?
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303 Posts
I get 21-22 :D
 

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Oh my f*ck!
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6,464 Posts
I got 23.5MPG on the way to LA (~180mi) this past weekend to get the new hood, and I was not driving anything remotely like a granny either. I can't tell you how many times my overspeed indicator (set to 90) went off.
 

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That's Got A V6 Right?
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303 Posts
dozlert said:
BCM? Birth control module?
Those are the buttons on the front seat. By the time you get the seat forward and do gymnastics to get in the mood is gone :p
 

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12 Second Club
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672 Posts
Discussion Starter #8
I had to ask too...i was told it is a "Body Control Module".

Hmmm....Baby goats :driving:
 

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I used ta could
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514 Posts
My mileage was good and manual calculations confirmed the DIC readout... and then it starting going lower and lower as the engine got better and better and the exhaust got louder and louder and my foot got heavier and heavier.

Sadly, I confirmed this with manual calculation as well.

On another sad note: I don't meet the eligibility requirements for the brain trust, but I am sure CMNT knows the answer to your question.
 

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Registered
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298 Posts
I've been running 15.8 to 16.2 per tank with an automatic. I'd be real happy with something in the low 20's. I only have 1400 miles on my car so, hopefully, it will get better. I do have a lead foot though!!!
 

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Deuce and a Half
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1,880 Posts
hmmm, body control module should have little to do with anything engine wise. It should be concerned with lighting, wipers, locks, security, etc

It probably also talks to the intruments, it may have been giving you the wrong signal the whole time. My question is, if you calc it by hand and that shouldn't be wrong at all, have you calculated it by hand with the new bcm or are you relying on its digital readout soley?
 

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LiqTenExp said:
hmmm, body control module should have little to do with anything engine wise. It should be concerned with lighting, wipers, locks, security, etc

It probably also talks to the intruments, it may have been giving you the wrong signal the whole time. My question is, if you calc it by hand and that shouldn't be wrong at all, have you calculated it by hand with the new bcm or are you relying on its digital readout soley?

Thats all the BCM does? I didnt know that.

Thanks for the info.
 

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12 Second Club
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672 Posts
Discussion Starter #14
So far, Im going by the guages. And of course the rapidly falling gas guage.

Guess i will go fill up and do a manual check to.
 

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2004 Torrid Red GTO
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1,119 Posts
I'm getting 18.5 driving pretty conservatively. I have noticed that my gas mileage has been improving. Going 80 @ 2400RPM on level terrain used to return about 18mpg, but lately it's been more like 23 under the same conditions (according to the BCM).
 

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Deuce and a Half
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1,880 Posts
After my mods I gained about 3 mpg on a 50/50 city highway mix. I haven't had it on a long trip yet but im sure itll gain about 2-3 up there also.
 

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Deuce and a Half
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1,880 Posts
BCM is kinda like the pilot/vehicle interface for those of you in defense lol. It should be dealing with wipers, windows, locks, security, cruise control, light timing, instruments, lighting inside and out, seatbelt warnings etc. It interfaces with a bunch of discretes and probably some get passed between it and pcm over a buss. I am just pulling that last part out of my butt since I have never looked at a detailed view of the electronics in this car but it would be good practice to do it that way. Anyone want care to share some detailed pictures, diagrams, or schematics? I am sure it would be helpful for general information.
 

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MAX-M6/LS1
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223 Posts
I thought mine was doing bad, not living up to the 29mpg window sticker. Being a 6 speed and having plenty of power I was getting 26-27 before all the mods and now I get 24-25mpg. Now that is if I drive like a sane person and keep the rpm's down. When I play I get 18mpg. I drive 100 miles a day and 60 of that is highway with the cruise control on. I have 13,000 on it now. So judging from the other posts I have nothing to complain about.
 

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I like boobs.
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6,581 Posts
It is possable that the stock unit 'learned' after a few thousand miles and eventualy your mileage went up once it tuned itself into your driving style. (In Hondas, this is called the Long Term O2 correction value and can vary the fuel maps by +/- 20% if necessary.)

Basicly, give it a month and it should correct itself again.
 

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Oh my f*ck!
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6,464 Posts
CSiJason said:
It is possable that the stock unit 'learned' after a few thousand miles and eventualy your mileage went up once it tuned itself into your driving style. (In Hondas, this is called the Long Term O2 correction value and can vary the fuel maps by +/- 20% if necessary.)

Basicly, give it a month and it should correct itself again.
I'm pretty sure that all cars do that these days. That's why you hear people talk about resetting the PCM before drag racing - set everything back to the default maps.
 
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