This is a 2008 LY2 4.8 in a Jeep , modded harness and flashed it runs but fuel MPG not to good and very light surge at highway speeds. I have checked volts and the ground at he o2 plug.

The local dealer said they might be failing after warming up so against my better judgement I replaced both O2 and yep no difference .

I'll be tracing wires today, (again)

Here are some live data I have no idea what some of this means. the cat temps I assume are actually o2 temp?? as there are no cats

This reading was after a short drive, the cat temps at speed were about 3x this

Ideas?

 

here are all the codes the first one will come up immediately after clearing the others after warm

the rear o2's are supposed to be deleted

 

Looks like the pink wires for the 02 sensors do not have 12v with the engine running. Does the pcm stay in open loop? That would explain your poor mpg, although 4.8s are not known for good mpg.

 

Nope just tripple checked that and hot both sides while running,

I traced each wire and here is what I found using a cut off end of a o2 sen , a small battery and test light.

I cant seem to find the correct pin out of the 2 big plugs that go to the ecu for MY engine. The ones I have would indicate the wires are WAY off . (hard to believe they are ALL off but possible I guess)

This is what they are

Sen 1 Bank 1

Tan "A" on sensor to pin 36 in X2 plug
Pur/Wht "B" on sensor to pin 37 in X2 plug
Grn/Wht "C" on sensor to pin 72 in X2 plug
D pink 12v +

Sen 2 Bank 1

My doc says these should ALL be in X1 plug but they are in X2 IDK if thats correct.

Tan "A" on sensor to pin 40 in X2 plug
Purp "B" on sensor to pn 39 in X2 plug
LightGreen "C" on sensor to pin 73 in X2 Plug
D pink 12v+

 

Don't depend on the free online diagrams, the 2007+ trucks have WAY more wiring variation from model to model compared to the older 1999-2006 trucks.

Here is some of my work you may enjoy lol

http://www.youtube.com/watch?v=eQ65gApMPyE

 

See the highlighted corrections below.

Sen 1 Bank 1

Tan "A" on sensor to pin 56 in X2 plug
Pur/Wht "B" on sensor to pin 57 in X2 plug
Grn/Wht "C" on sensor to pin 12 in X2 plug
D pink 12v +

Sen 2 Bank 1

My doc says these should ALL be in X1 plug but they are in X2 IDK if thats correct.

Tan "A" on sensor to pin 60 in X2 plug
Purp "B" on sensor to pn 59in X2 plug
LightGreen "C" on sensor to pin 13 in X2 Plug
D pink 12v+

 

Cool vid,

And Im going to the dealer friend of mine and get him to print me a pin out from my vin #

Mine runs ok but with a slight surge at speed, and it just bugs me it has those codes LOL and its got to be hurting MPG

Here is my rev up :-)

 

Based or your pins mine are ALL wrong and the pins you list above is what I have should be as well . What about the X1 and X2 plug diff also? My doc shows ALL the wires to sen Bank 1 , 2 to be going to X1, see below

[IMG]http://www.lt1swap.com/pictures/Engi...20-%20HO2S.gif[/IMG]

 

If I read this right. are the Driver side front and back o2 in X2 plug and both senor 2s on passenger side are in X1 ?

If thats true then this is my problem. As both front sensors of mine are in X2

 

well I went to the dealer and I had it all confused lol. First I was counting the pins from the wire side, thats not correct, it must be counted from the pin side.

Then I was confused by the Bank 1 and 2 thing. It seems that Bank 1 is driver side and Bank 2 is passenger side (not front and rear like I was thinking)

But that adds another mystery as the programmer insists that the rear O2 were deleted but some of the codes are for sensor 2 (that dont exist !!!!)

But over all the dealer said that the codes were having no real affect on running just for the time it takes for the o2 to come up to temp after that he said they were functioning normally.

If thats true the only thing for me is the MIL light on all the time. No big deal as its unplugged anyway. So it sounds like the experts say what I have been doing,,,, drive it LOL It just bugs me that it seems like something was programmed wrong.

Anyone know someone that would be willing to scan it and re flash ? (that knows what they are doing) ??