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Ron
Ron, ASE Certified Technician
Category: Jeep
Satisfied Customers: 35527
Experience:  34 year working in the automotive field as a Tech.
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My name is matt. my sons 1998 jeep cherokee the tail lights

Customer Question

Customer: my name is matt. my sons 1998 jeep cherokee the tail lights are not working. Everything is working brake lights, reverse and turn signals. I have checked fuses they are fine. The only one I am having problems with is under the hood. #21 & 22 its a 20amp fuse keeps blowing. It might be 20 and 21 can't remember. All I know is I can put a new fuse in it and it will be fine until I turn on the headlights then it blows.
JA: Thanks. Can you give me any more details about your issue?
Customer: I unhooked everything in the back taillights and towing lights. still blows the fuse. #7 & #23 fuses are fine
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Customer: Yes
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Submitted: 1 year ago.
Category: Jeep
Expert:  Ron replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

If the fuse that blowing is #20, Check the wiring going to the rear Oxygen (O2) sensor. There have been reports of the wiring rubbing on the driveshaft, causing the fuse to blow. Repair wiring as needed. Check this for me and post back with the results and we can work from there if need be.

Customer: replied 1 year ago.
My main concern is the tail lights and parking lights they are not working.
Customer: replied 1 year ago.
Will that O2 sensor cause the taillights not to work
Expert:  Ron replied 1 year ago.

If itd blowing the fuse yes. The fuse blowing indicates a short to ground in the circuit.

Customer: replied 1 year ago.
Ok will try looking tonight
Expert:  Ron replied 1 year ago.

Sure thing, Im here if need be. Good luck.

Customer: replied 1 year ago.
Well I looked at both sensors could not find a bare wire
Expert:  Ron replied 1 year ago.

Are you still blowing the fuse and if so which one is it, 21 or 22?

Customer: replied 1 year ago.
According to the Internet pic of the fuse box under the hood it's showing a 20amp for O2 sensor relays. It's not label as a number.
Expert:  Ron replied 1 year ago.

Okay then go back and unplug all the H02S sensors and see if the fuse holds. If so then start plugging them in one at ta time and see if you can get the fuse to blow, if so then suspect you have a shorted HO2S sensor.

Customer: replied 1 year ago.
Ok will try that tonight. How many sensors should there be
Expert:  Ron replied 1 year ago.

There should be three or in some cases 4. Unplug them all and see if the fuse holds. If so, go back and plug them in one at a time to see if you can determine which one is causing the fuse to blow.

Customer: replied 1 year ago.
Ok will try thank you
Expert:  Ron replied 1 year ago.

Your very welcome and thank you as well.

Customer: replied 1 year ago.
Well unhooked o2 sensors still blowing I looked again it's fuse #21  21 is showing PCM ignition coil and 22 is showing fuel relay switch
Expert:  Ron replied 1 year ago.

So which one are you blowing? Which ever one it is indicates you have a short on that circuit.

Customer: replied 1 year ago.
The fuse #21&22 under the hood
Expert:  Ron replied 1 year ago.

Okay so which one is blowing?

Customer: replied 1 year ago.
The only diagram I have shows 21 is PCM ignition coil relay and 22 shows fuel pump relay
Expert:  Ron replied 1 year ago.

Okay I understand that but which one is blowing?

Customer: replied 1 year ago.
They are both on the 20 amp fuse one side of fuse is 21 and the other is 22 they are together
Expert:  Ron replied 1 year ago.

They can not be on the same circuit, they are for separate circuits . So you saying they are both blowing?

Customer: replied 1 year ago.
I'm sending a picture of the fuse box under the hood. The 20amp fuse at 21 & 22 is the one that is blowing.
Expert:  Ron replied 1 year ago.

Okay I have the diagram, in your first question you said the fuse was blowing. In order to point you to the right circuit I need to know which one that is blowing. Is it 21 or 20 or both?

Customer: replied 1 year ago.
Both same fuse
Expert:  Ron replied 1 year ago.

Okay Im not sure what you mean the same fuse, 20 is the flasher fuse and 21 is for the computer and ignition system.

Customer: replied 1 year ago.
I might be looking at wrong diagram I will take a pic but the pic I sent you 21 and 22 f17 is the fuse that keeps blowing. You know more about it than I do
Expert:  Ron replied 1 year ago.

Fuse 17 is the headlamp circuit as well as the data link connector

Customer: replied 1 year ago.
Ok so what should I do. I was told to replace the light switch. What do you think
Expert:  Ron replied 1 year ago.

If its the #17 fuse blowing I would be looking at the tail light circuit. Check the wiring going to the left and right park lights and the license plate light for any signs of a short to ground.

Customer: replied 1 year ago.
Ok will look
Expert:  Ron replied 1 year ago.

If its the #17 that blowing then its likely in the tail lamp circuit.

Customer: replied 1 year ago.
Ok
Customer: replied 1 year ago.
Thank you
Customer: replied 1 year ago.
Do you have a diagram of the wires
Expert:  Ron replied 1 year ago.

See them below.

https://dl.dropboxusercontent.com/u/104923897/Tail%20lamp%20JAn%2010.pdf

https://dl.dropboxusercontent.com/u/104923897/Tail%20lamp%20%232%20Jan%2010.pdf

Customer: replied 1 year ago.
I re-wired so I thank you
Expert:  Ron replied 1 year ago.

Glad to hear you got it resolved and thank you as well. Please take a moment to rate my service so I can get credit for my time, the question remains open for follow up even after doing so, all you need to do is return to this question if need be.

Thank you again.