trust96xj

Rough idle. Even more so while in park or neutral. Cel on for o2 but I just replaced it. Can't figure out if it has a fuse or not. What all can cause a CEO light for an o2 that's not technically the o2 being bad?

DFlintstone

I guess you are talking about a 4.0 in a 96? Posting the code really helps....guess you would start with a tune up, check vacuum leaks. Cleaning the throttle body and IAC.....Also I believe there is a fuse and a relay for the 02 heater. It's not rare the wires to the 02(s) get melted/ground and cause problems....

You can try this. I hear sometime in 97 it no longer works.
1984-1990 w/AMC engine are pre-OBD.

1984-1986 w/GM V6-173 are OBD-I (GM control setup.)

1991-1995 are OBD-I (Chrysler)

1996-2001 are OBD-II (Chrysler)

The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

Newer (OBDII) models - Put the key into the ignition, push down the odometer reset button, then turn the key to RUN with your finger on the button - and then release the button. The odometer will go through 1111111 through 999999, then display the car's serial number. It will then show the error codes (it might show them starting with P). If this method does not work, try the OBDI method.

trust96xj

Yea 96 4.0. I don't remember the obd2 code but they're both o2 out of range. Bank 1 sensor 1. So it's my pre cat. But I just replaced both of my o2 sensors. And I can't figure out where the fuse or relay would be.

DFlintstone

Maybe there is something here..https://www.google.com/search?tbm=is...2-7l7l0.frgbld.

tjwalker

The oxygen sensor heater circuit on your 96 is fused. The fuse is in the power distribution center (black box) under the hood on the passenger side.

It is a 15 amp mini fuse. Not exactly sure of the location but somewhere in the 19-24 area.

Check EVERY fuse before moving onto other more complex possibilities.