Re: 99 4.0 o2 sensor problems
If your jeep is indeed federal only (not california) you will have only 1 main cat instead of that plus 2 mini-cats. On federal there are 2 O2 sensors, 1 each before and after the cat. On California there is 1 before and after each mini cat. So, this code is kind of confusing if your truck is only federal. My guess is it would be the after cat sensor.
My Jeep: 2001 Grand Cherokee Limited, 245/65R17 Falken Rocky Mountain ATS, K&N drop in air filter, Bilstein HD's. De-badged, eagle-eye LED Tails & LED 3rd brake light, Addco front and rear sway bars, Superchips tuned & TM snip, interior 6k LED's, Gen3 ccfl projectors with Volt 6k HID lows, akebono brake upgrade with R1 Concepts premium rotors.