# EPC light turning on and off



## CorvetteKillerVr6 (May 9, 2007)

just put in a new MAF sensor and the light went away for a bit,
but now it'll come on everynow and then but turn off soon after.

i think my temp sensor might be pouched aswell cause once its warm it has a hard time starting


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## The Popemobile (May 3, 2006)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

hard hot starts are indcative of a faulty fuel pump check valve...replace the valve if avail seperate from the pump, otherwise, replace the pump


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (The Popemobile)*

its weird...

it goes on after running great for even a couple hours....









then after about 10-20 minutes it goes off again.
im scanning to codes tomorrow and il see what i end up with.


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

well i figured it out a little more.
im getting the same original code for having deleted the SAI (P1432)
but that ones fine.
the one thats causing the EPC bull**** is (P0101), which i think is still a code related to my MAF sensor.
which i just replaced.....









soooo, ive been reading on a few other posts about how i could possibly be having flow issues in the 4" intake system.









anyone know anything about this??
ive seen guys making flow straiteners? 


_Modified by CorvetteKillerVr6 at 1:36 PM 7-23-2009_


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

ttt


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## skateaholic247 (Jun 7, 2009)

*Re: EPC light turning on and off (The Popemobile)*

i'm having the same problem right now....
it started yesterday and my EPC light willl come on, then turn off shortly after.
i havent even been driving around much and it'l come on, and go off after a few minutes, or if i turn the car off, by the time i start it again its off.
there's no decrease in performance or anything major like that, car is still running smoothly..
any ideas what might be the problem?








i still need to get an airbag light taken care of too..


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (skateaholic247)*

are you turbocharged?
i am and ive got a 4" intake pipe after my 4" filter and 4" MAF housing and i think there some turbulance tripping the maf out.
apparently thats what happens with a 4" with a certain shape.


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

its still doing this rarely, but everynow and then.
it seems to happen more when its sticky and humid out.....


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

anyone??


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

ive heard stuff about how my 4" custom intake pipe i made could be causing some sort of turbulance in the intake thats making the MAF sensor freak out.
my intake consist of a 4" k&n filter/ 95mm I.D (4"O.D) MAF housing / 4" intake pipe about 20 some odd inches long / and a 4" to 3" 90 degree silicone elbow going into the 3" turbo inlet....

is some sort of turbulance actualy whats causing this??


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

I've heard of guys using "air straighteners"...?

can some one enlighten me


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

AND as of tonight ive eliminated one other option i thought it could of been.
For the turbo project i extended the Throttlebody wiring to the front of the car for the SRI and i thought that the extra bit of wiring harness was causing Throttle body sensor issues.
it was a bit longer than it had to be, so ive made a nice new extension harness thats the perfect length, but it still came on after about a good hour of solid cruising...............















so now my options are either (T/B adaptation needs to be done, or the MAF sensor is freaking out cause the 4" intake maybe???)
its really starting to frustrate me, cause when the lights off, the car hauls ass and runs soo strong and idles good and everything. i just dont get it.
wish i had some help on this one, i guess i should just invest in a VagCom setup and be done with it, id have my anwser right away 
i know im getting the following codes
P0101( Mass Air Flow (MAF) Circuit Range/ Performance Problem.)
p1432( secondairy air injection) this one is being ignored for now,till i can have it deleted 
p1142 (- Load Calculation Cross Check Lower Limit Exceeded)








i just dont get it, 

anyone???????


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

I also have the MAF wiring extended from the driver side over to the passenger side, and is there anyway that i used to big of a gauge of wiring??
its quite a bit bigger than the gauge of wiring out of ther stock MAF harness plug....
i think i used 18 gauge.
maybe its too big,causing some sort of impedance problem..


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

Has no one ever had this problem with there VRT????????????????????????????????????????????


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## KubotaPowered (Jan 27, 2005)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

What kind of wire did you use, copper or aluminum? What did you use to make your connections to the stock harness?


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (KubotaPowered)*

im pretty sure i used copper primary wire, soldered each every connection to the stock plug and harness and shrink wrapped everything.

but i think i used like atleast 16 gauge wiring, which is much bigger than the stock stuff.
i used this gauge on both the t/b extension and the MAF extension.
im thinking it might be throwing off the sensor..??


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

So tonight i rewired both the t/b extension and the MAF extension and match the wiring to the identical gauges that are in the stock harness.

the maf has one 18gauge wire and four 22gauge.
the t/b has 6 that i used 18 gauge on all of.
didnt make a difference at all.
cruised for about a half hour, felt great, then this ****in EPC light came on again.
and to be honest im getting really fed up with it, it seems to burn so much more gas when that light is on!









it sucks big time


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## sgolf2000 (Mar 2, 2003)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

wire gauge should not make much difference. i would guess an issue with airflow to the maf. i looked at a guys jetta in my neighborhood who was throwing the epc light and it was because he put a cheap 2.5in filter with a reducer onto his maf, which messed up the flow. is your maf right on the filter?


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (sgolf2000)*



thats how mine is setup.

4"x 9" k&n filter to the 95mm maf housing, then the rest is all the same size 4" intake pipe all the way back.
could the filter be too big??


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## KubotaPowered (Jan 27, 2005)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

A. There is too much of a straight shot to the turbo and nothing in the way to break up any swirling air ahead of it. I had a similar set up witha mandrel bent 45 degree bend just ahead of the turbo and the AFRs would dip into the 9's.
B. C2 software works better with a 3 inch draw pipe.


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (KubotaPowered)*

is there any way of making an air straightener??

i have some Lexan plastic and was thinking of cutting a 4" circle and drilling tons of holes into it like some honey cone....
and placing it right before the MAF housing/
think that would work??


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## KubotaPowered (Jan 27, 2005)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

I wouldn't make one out of lexan. I can only imagine that wouldnt end well if the turbo ended up munching on it. Check out this link, this is what a proper straightener looks like
http://dieselpowerproducts.com/Turbo_Air_Guide.php


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (KubotaPowered)*

yeah thats what im thinkin.
i got a buddy hunting for a 95mm O.D( roughly 3.74" O.D ) air straigtener from the yard he works at that i could put inside the MAF housing before the sensor.

hopefully he comes up with something soon, im waiting on a new turbo from Clay tomorrow so i can slap it on and head to Quebec to have it tuned by Uni and cruise back with them to Vagkraft!


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

so i got a 95mm air straightener off a 2003 GMC sierra and it fit perfect inside my MAF housing Juan made me.

and it seems to make a huge difference in the way the car feels!
and now the light wont come on for a few hundred km's.
but its still coming on!!
im in Montreal right now and ill be visiting the Unitronic shop this afternoon to have them Vagcom the ECU and hopefully figure things out for me. needs a throttle body adaptation and what not.

wish the luck http://****************.com/smile/emthup.gif


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## KubotaPowered (Jan 27, 2005)

*Re: EPC light turning on and off (CorvetteKillerVr6)*

Its amazing what one of those will do for the driveability of the car. Check your connections as well, make sure there aren't any that are loose or broken


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## TONYESC76 (Jul 4, 2007)

*Re: EPC light turning on and off (CorvetteKillerVr6)*


_Quote, originally posted by *CorvetteKillerVr6* »_so i got a 95mm air straightener off a 2003 GMC sierra and it fit perfect inside my MAF housing Juan made me.

and it seems to make a huge difference in the way the car feels!
and now the light wont come on for a few hundred km's.
but its still coming on!!
im in Montreal right now and ill be visiting the Unitronic shop this afternoon to have them Vagcom the ECU and hopefully figure things out for me. needs a throttle body adaptation and what not.

wish the luck http://****************.com/smile/emthup.gif 

do you have a pic of what your took off the gmc? was it a gas or diesel truck?


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## KubotaPowered (Jan 27, 2005)

*Re: EPC light turning on and off (TONYESC76)*


_Quote, originally posted by *TONYESC76* »_
do you have a pic of what your took off the gmc? was it a gas or diesel truck?

click this link
http://dieselpowerproducts.com/Turbo_Air_Guide.php


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (KubotaPowered)*

So here's the anwser gentleman........

while in Montreal this week, i got to visit Unitronics new shop today!
and its definatly incredible, engine dyno room and all.

sick sick place to hang out for the day!








either way, Michel helped me out getting to the bottom of this.
turns out the MAF housing they write the 440cc program with is a Audi A8 housing, which is around 3.50" the one i had made by Juan is is a 4"I.D(95mm)housing, the same as the C2 motorsport setup.
sooo, turns out the sensors are suupppeerrr sensitive to any size increases in the housing, buttt
Michel was able to fine tune it to work with the 95mm housing i had.

In the end, no EPC light all day for the first time since its been running on boost,
1500km or so.

im a happy boy









runs like a champ now,im installing the new Rotomaster tomorrow too!


_Modified by CorvetteKillerVr6 at 9:18 PM 8-12-2009_


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## TONYESC76 (Jul 4, 2007)

*Re: EPC light turning on and off (KubotaPowered)*

thanks... glad to hear your car is running good now http://****************.com/smile/emthup.gif


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (TONYESC76)*

and it also turns out that the air straightener is a must for any chip tune!.

i used the straightener out of a 2003 gmc sierra maf housing.
its a Delco product and it did take some gentle force to get the straightener out as it is one peice with the whole housing.
but it worked great


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## boravr6NS (Jan 5, 2008)

*Re: EPC light turning on and off (CorvetteKillerVr6)*


_Quote, originally posted by *CorvetteKillerVr6* »_So here's the anwser gentleman........

while in Montreal this week, i got to visit Unitronics new shop today!
and its definatly incredible, engine dyno room and all.

sick sick place to hang out for the day!








either way, Michel helped me out getting to the bottom of this.
turns out the MAF housing they write the 440cc program with is a Audi A8 housing, which is around 3.50" the one i had made by Juan is is a 4"I.D(95mm)housing, the same as the C2 motorsport setup.
sooo, turns out the sensors are suupppeerrr sensitive to any size increases in the housing, buttt
Michel was able to fine tune it to work with the 95mm housing i had.

In the end, no EPC light all day for the first time since its been running on boost,
1500km or so.

_Modified by CorvetteKillerVr6 at 9:18 PM 8-12-2009_

I seem to remember mentioning this to you back in may when first fired it up..







c2 95mm.....uni audi a8


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## CorvetteKillerVr6 (May 9, 2007)

*Re: EPC light turning on and off (boravr6NS)*









i think i do recall.......

yeah but its crazy how the difference is only lie 3mm
its insane.
either way, i now have a custom tune setup from Unitronic especialy for my 95mm I.D housing









they say im the first one theyve tried this with








so far so good. http://****************.com/smile/emthup.gif


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## boravr6NS (Jan 5, 2008)

ah yes 3mm, however, flow is proportional to area, therefore diameter squared!!








It's good that they have this figured out now, this was one of the reasons i went with c2 when i changed from the 36# to 60 # tune. I wasn't sure if they could do a custom tune....And they never answered any of my emails.
Did they charge you for the remap?

_Modified by boravr6NS at 11:33 AM 8-28-2009_


_Modified by boravr6NS at 11:33 AM 8-28-2009_


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## CorvetteKillerVr6 (May 9, 2007)

*Re: (boravr6NS)*

Nah, there hook me up and spend probably an hour or two helpin me out.
there great guys.
there moving into there new bigger facility, and theyll get better anwsering and what not.
http://****************.com/smile/emthup.gif 
seems to have fixed it so far!
cars running strong


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