Jeep Wrangler Forum

Jeep Wrangler Forum (
-   TJ Tech Forum (
-   -   Scan Tools to check backfire issue (

Kodiak Commando 06-15-2008 10:47 PM

Scan Tools to check backfire issue
I had a wierd event take place on my 05 Rubicon Unlimmited the other day. It has the automatic and has 47k miles on it. I was pulling a tent trailer up a steep hill (out of Oakhurst, CA) and there was what sounded like a backfire. The check engine light came on and power was down to 15% of what it was. I disconnected the battery to clear and reset the computer and it worked much better but still not 100%. It got me home anyway. It ran well all week without throwing codes so we took it wheeling yesterday. You guessed it, the check engine light came back and the power, while not as bad as the first event, is down 20% or so.
Anyone have recommendations on a code reader? I don't want to clear the check again without seeing what was reported.

whitebuffalo 06-15-2008 10:49 PM

does the key on off trick work on jeeps? turn the key on, then off, then on, then off, then on again and it shows the codes (on dodge OBD2 at least)

Triple88a 06-15-2008 11:29 PM

go to autozone, they should have free code checks. They will read your codes for free.

Once you get the codes you can find what it really is.

Kodiak Commando 06-17-2008 11:42 PM


Originally Posted by Triple88a (Post 237788)
go to autozone, they should have free code checks. They will read your codes for free.

Once you get the codes you can find what it really is.

Thanks for the lead! I went to autozone and borrowed their code reader. It showed PO431 Warmup catalyst below threshold (bank 2). Headed to the dealer and am having them replace it under California Emmissions Warranty. Of course that doesn't explain why there was enough fuel in the exhaust to ignite and blow it out! We'll see what happens after I get it back. Ahhhhh Jeep mysteries, you gotta love em. :rofl:

Kodiak Commando 06-19-2008 12:15 AM

So the answer is in! The injector wires melted from the heat from the warm up cats. That's the reason for the backfire as it was dumping fuel due to being shorted "on". The explosion and short freaked the computer into limp mode. When I disconnected the battery, the computer was reset and the injectors worked reasonably enought to get home. The dealer replaced all three cats and the exhaust from the muffler forward and fixed the melted wiring. I noticed the routing is safer that the way it came now as well.
Moral of this story, check your injector harness proximity to the exhaust!

MOz 06-19-2008 06:18 AM

Good information.

Triple88a 06-19-2008 01:14 PM

good to know, what did she cost you for the repair?

All times are GMT -5. The time now is 11:48 PM.

User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.