P0138 & P0463 at same time

Hi everyone, 98 XJ 4wd 4.0 automatic
P0138- Oxygen sensor high voltage bank 1 sensor 2

P0463- Inaccurate fuel level reading





A few months back I got the P0138 code. I had a spare (but used) O2 sensor on hand so I slapped it in and that fixed the problem. I was sure to verify the connector was clean as well. Fast forward 5 months and now I have the same P0138 code as well as the P0463 code at the same time. My fuel gauge does only read intermittently but I have two Cherokees and over the past 15 years I have never found a replacement fuel pump that doesn't stop reading fuel levels within a year of install. I have never gotten a code for it before.



Do I just assume the replacement (used) O2 is bad and replace it along with a new pump and sending unit assembly? Or are there some other issues I could look into (at least with the 02 issue.)

The 02 sensor the code is for sensor 2 that is the 02 sensor that is after the catalytic , I would say your cat is going bad .

It's possible the cat is going, but it's not throwing a code for cat efficiency though. I would actually suspect the wiring is damaged or the sensor is bad first.

lawsoncl said:

It's possible the cat is going, but it's not throwing a code for cat efficiency though. I would actually suspect the wiring is damaged or the sensor is bad first.

Click to expand...

That's a good point .

Start with obvious, test the sensor, and inspect and test the related wire plug and wire harness.

Thank you all, that cat is original with the vehicle so it wouldn't surprise me if it was going bad. I will have to test the O2 and will check the wiring again just in case something changed from last time. You guys are awesome as usual.