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2005 WK 04-16-2012 11:52 PM

Module wiring, Fuel Saver MPG?
So i was down in the passenger side kick panel the other day and noticed there was a small module looking thing. It says "fuel saver mpg" and has an on and off switch. I followed the wire for it through the firewall and its spliced into the module on the inside of the passenger side fender. The fuel saver doesn't seem to be doing anything and the light on it doesn't even turn on so i don't even think its wired correctly.

I wanted to take it out but i wasn't sure how i would go about doing so. If i unplug one of the harnesses on the module on the inner fender, will i mess up anything? I know i should always disconnect the negative cable but will i have to get my system reflashed if i unplug anything?

Ive had a check engine light on for over 2 years now and i think I've finally found the problem (or i hope so). Basically, the wires on the harness that are suppose to plug into the jeeps module are cut and ran into the fuel saver instead. I need to reconnect the 6 wires to the module but I'm just not sure if i can unplug the harness to do so. Any input would be great, thanks in advance!

SvenskaJeepGuy 04-16-2012 11:59 PM

Re: Module wiring, Fuel Saver MPG?
that thing looks sooo bogus, i would remove it and make sure all the wires are redone correctly. i would also recommend removing the negative first. you shouldnt need anything to be reflashed. hopefully that fixes your problem, what codes are you showing?

2005 WK 04-17-2012 12:26 AM

Re: Module wiring, Fuel Saver MPG?
thanks for the quick response man. Im gonna give it a shot tomorrow and hopefully its not to hard to redo the wiring. Im getting p0420 p0430 and p2096. Ive replace my converters less than a year ago and i was still getting the code even after they were swapped out.

Madanio24 04-17-2012 10:34 AM

Re: Module wiring, Fuel Saver MPG?
Yea definitely doesn't look legit.

2005 WK 04-17-2012 09:01 PM

Re: Module wiring, Fuel Saver MPG?
So i took it off earlier today and reconnected the wires the way they should have been, so far the check engine light hasn't come back on. Im gonna do a few days of driving since my computer was reset from disconnecting the battery. Hopefully this was the solution to my light that has been on forever.

jeepgcoman 04-17-2012 09:07 PM

Re: Module wiring, Fuel Saver MPG?
I concur with all of the above. Their narrative about this thing is just double talking jibberish. The codes you have are all O2 sensor/cat. system related. It's just too bad you had to replace cats. that were probably not defective. Good luck on the removal and let us know if the codes go away. Unless you reset them with a code scanner, it'll probably take 3 good trips (run cycles) to shut them off.

2005 WK 04-18-2012 02:36 PM

Re: Module wiring, Fuel Saver MPG?
Light came back on today, only for p0420 and p0430. I guess I'm done changing parts for now, I've put way to much money into this thing since i bought it. Thanks for everyones input and help tho

01grand 04-18-2012 02:54 PM

Re: Module wiring, Fuel Saver MPG?
If this device was messing with your O2 sensors theres a chance it could have screwed up the cats, or that the sensors are bad.

jeepgcoman 04-18-2012 03:38 PM

Re: Module wiring, Fuel Saver MPG?
The P0423 and P0430 address both left and right bank FRONT O2 Sensors. It'll only cost ~$60-100 for both of them, plus any labor....unless you do it yourself. If they are indeed bad, your fuel economy probably sucks, as they tend to go toward the rich side when they fail. Run them bad too long and you'll end up changing the cats. again. Here's a thread I did on O2's when I had a problem. Hope it helps you in your decision process:

2005 WK 04-20-2012 01:41 AM

Re: Module wiring, Fuel Saver MPG?
Thanks for the post, I changed my O2 sensors about 2 years ago. I had the same codes before and even after I changed all 4 sensors. I replaced the cats with the magna flow ones a few other members on here have used and they claim they have no issues with them. Im thinking at this point the only way to get rid of the light is to get OEM cats which i got quoted $990 for. I think ill hold off on those and drive it the way it is.

jeepgcoman 04-28-2012 08:42 PM

Re: Module wiring, Fuel Saver MPG?
If you have one of the aftermarket tuners, you could do some data logging and see what kind of millivoltage readings you're getting from each of the sensors. That will for sure tell you wassup with them.

robertanderson 05-18-2012 05:07 AM

Re: Module wiring, Fuel Saver MPG?
Well, Everyone wants their automobile to be more fuel economical. Not all gasoline savers are what they're cracked up to be. However, here are some snake oil gas-saving devices that have been thought of by numerous automotive market sources to be fuel-saving hoaxes.

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