I need some help. I am a 23 year old DIYer...and am not the best when it comes to electrical gremlins.

My CEL light came on after about 2 weeks i had a remanned 4.0L put in with better pistons. I looked under the XJ and saw I must've ripped the wires from my O2 sensor on the CAT when I was climbing through snow

Anyways, I went to replace the O2, of course no anti-seize was used before so I couldnt get the O2 out without taking a part of the cat with it. I took this as an opportunity to weld in a new magnaflow CAT with O2 slot, and Flowmaster 40 series, new bosch O2 all hooked up and tucked up.

Reset the battery/ECU, still have the CEL on. So I run to the "trusty" autozone and have them pull the codes- they can't connect it. It won't read anything. I went to O'Rielleys and had the same experience. I thought it was a simple O2 fix- it acts like I don't have a new one in either. I can smell gas out the exhaust- rich.

1) Wouldn't my mechanic that put in my remanned motor, have to use the OBD2 port to read that the motor is running things at right temp/volt/pressure?

2) Where do I start to try to read the codes the CEL is throwing?

All my sensors work, and work well. ( I manually tested it.)

I appreciate the knowledge in advance.

 

There's a grounding wire bolted on the stud where the oil dipstick bolts on the block, it's for OBD2 connection. Make sure the wire is properly bolted on the block, or if it's already bolted on, clean the connection.


Also I wouldn't trust that Bosch O2 sensor. NGK is the best as seeing as it was the oem brand.

 

Here's a fuse layout for the PDC. This is a '99 but the '98 will be the same.


Check the O2S Heaters fuse.

 

I found a wire near the Alternator that looks as if it is a ground, freely hanging. But its not near the dipstick/block area at all. I don't see a ground near the dipstick in general.

The fuse is still fine. Thanks for the info thus far!

 

Here's the ground point area you are talking about- I think.


Note the small ring terminals listed in the pic.


Below this is a pic of the ground point at the dipstick. It's the ground for the data link connector.

 

Is the first pic near the alternator, looking upward? Sorry, new to Jeeps...this one is racking me..

 

Yes, if you were laying on your back under the alternator it would be right there. Note the location of the coil mount bracket.

 

that's great pictures, I just saved them.

 

Thanks for the update! It is hanging loose near the alt. It doesn't look like I can ground it anywhere though (my underneath is not as clean looking as yours is LOL)

Nor does it have the small terminals like you show... I will update with a picture tomorrow when I can get it under some light and a lift at work! (Love big *** hi-lo's)

 

Did you check the O2S heaters fuse in the PDC?


Do your headlamps work? The fuse for the headlamps also powers the data link connector.


Did you check to see if the wire(s) are hooked up at the oil dipstick tube? These are the grounds for the data link connector.


If the grounds at the coil mount bracket weren't hooked up you would loose some functions, like the PCM and TCM. Or the transfer case light or O2S heaters.


The ring terminals for the grounds at the coil mount bracket look like the ones in the pic below. The connector is for the coil.

 

Did you check the O2S heaters fuse in the PDC? YES. All good.

Do your headlamps work? The fuse for the headlamps also powers the data link connector. Yep, they work,

Did you check to see if the wire(s) are hooked up at the oil dipstick tube? These are the grounds for the data link connector.

If the grounds at the coil mount bracket weren't hooked up you would loose some functions, like the PCM and TCM. Or the transfer case light or O2S heaters. Would this cause VERY POOR MILEAGE? And just a CEL that can't be read?



BRB, taking pics..

 

.

 

To the left is the alternator, and on the right is the mounting nut that this wire goes too; I assume/..

 

Hard to make things out in your pic.


Is there two larger wires connected at the two studs at the coil mount?


One should go to the battery and the other to the alternator.


I will look this thread up in the morning...got to go.

 

Do you have an upgraded Alternator?


Do you have upgraded ground cables?


You can check to see if you have power at the Data Link Connector (DLC) from inside the vehicle.

If possible, use a digital Volt/Ohmmeter.

Below is a diagram of the DLC pin cavities.

Pin cavity 16 is power, coming from fuse 17 in the PDC.

Pin cavities 4 and 5 and the grounds that are attached at the oil dipstick tube attach stud.

Using the voltmeter, touch pin cavity 16 with the (+) probe and pin cavity 4 with the (-) probe. You should see battery voltage. Repeat test using pin cavity 5 as the ground. Do not shove the meter probes in to the pin cavities. Inspect the pin cavities for corrosion.

If you don't get battery voltage, Inspect/clean the wire connection at the dipstick attach point.




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