Joshcherokee1997

My check engine light is.on for high voltage to both o2 sensors and it keeps blowing the oxygen sensor fuse. But i have no clue why its already gone through 3 what could it be?
Thanks for any help

Joshcherokee1997

fuse 11 in fuse box under the hood.

salad

Which fuse are you blowing? There's one for upstream and one for down.

High voltage codes are usually cause by a wiring harness that has been shorted out, jumping the heater +12V and other wires. I'd look around your manifold for melted and hanging wires, as well as underneath by the drive shaft

Joshcherokee1997

it says fuse 11 labeled auto engine shut off and oxygen sensors its the only fuse that has blown then set CEL off. but i will look for wires that could be shorting it out. but wouldnt a loose wire cause other fuses to blow?

salad

Not if its the harness feeding an O2 sensor lol

CCKen

There is no fuse #11 in the fuse box (aka, Power Distribution Center (PDC)) under the hood on a '97 XJ.

Are you sure you have that right?

There is a fuse #11, however, in the Junction Block (JB) that feeds the following:

ASD Relay
Cooling Fan Relay
A/C Comp Clutch Relay
Fuel Pump Relay
TCM
PCM
Duty Cycle Evap/Purge Solenoid
Tans Range Switch

Does this ring a bell?

Joshcherokee1997

really im looking at my manual now and it is in my PDC and say slot 11: 15 amp blue auto shutdown, oxygen sensor. and thats the one that keeps blowing

CCKen

What manual are you looking in?

Here's an image of a 1997 XJ Body PDC, taken from the 1997 XJ Factory Service Manual. Can you tell us which fuse it is that you call fuse #11.



Here's a photo of the 97-99 PDC showing various fuses.

Joshcherokee1997

its the 7-8 one labeled O2S Heaters, but my manual is the one that came with the jeep and is labeled different

CCKen

The manual that came with your Cherokee is probably the Owner's Manual. It shows the fuse arrangement in the Junction Block (JB) in the passenger footwell.

Here's the 1997 XJ Body Junction Block. Fuse #11 powers the Powertrain Control Module, The Automatic Shut Down Relay control coil, and the Fuel Pump Relay control coil.

If F11 in the JB blows your Cherokee will come to a stand still.

CCKen

To isolate which O2S heater is blowing the fuse you can disconnect the downstrean O2S and try starting the engine with a fresh fuse in the PDC and see if it blows. If not I would suspect the upstream O2S as being at fault. If it it blows, leave the downstream O2s disconnected and disconnect the upstream, and try it again. If the fuse still blows you have a short in the wiring way upstream of both O2S's. If it blows, well, you found the bad guy.

Commonly, the harness for the upstream O2S gets chafed where it passes over the intake manifold on its way down to the upstream O2S connector. Check the wiring at this spot and along its run up to the fuel injector wiring manifold. Also check the wiring as it leaves the fuel injector manifold at that wicked bend it takes, for chafing/shorting to ground.

The downstream O2S wiring gets butchered in the drive shaft if the connector isn't secured properly. Inspect this wiring for chafing, etc.

Edit: What brand O2S's are installed? Bosch? NTK are the OEM O2S's.

nickxj94

Had this problem with my 2000 xj I had to change both o2 sensors I used Bosch from Oreally haven't had a problem since.

Joshcherokee1997

okay ill try that tonight

salad

Have you looked for melted/chewed wires yet?

nickxj94

Mine was shorted on the o2 sensor wires close to where they go in the sensor