TLR FUSE 21 is popping at a complete random, no visible bad wires, no bad ohm reading between fuse and pcm.



Guys, please, I am pulling my hair out, my teeth out, ripping my eyes out with this issue.

just purchased a 99 Cherokee sport and it clearly has a wiring issue.

PO stated the issue when selling: “p21 fuse will pop randomly” he also stated “in the three years this has been an issue, I only have to replace it maybe 1 or 2 times every 5-6 months”

I have owned it since this Saturday​​​​, and I have personally had to put in 37 fuses. But it’s not what you think. Hear me out.
Fuse 1: popped and then I touched battery cables together to reset pcm and it was fine.
Fuse 2-14: back to back popping immediately upon start up
fuse 15: popped +\- 45 seconds after startup
fuse 16-28: back to back again immediately upon start up

this was all in the first 2 days of owning it.

did some research found fuse 21 is powering ignition coil, fuel injectors, and pcm.

did my due diligence and check what wires I could see and can’t find any glaring issues. Decided I would replace the ASD relay.

no issues for 3 days, drove 411 miles across the state etc bumpy roads no issues.

then today happened. I changed nothing. Was going for a small drive this evening and blew a fuse in a way I havnt yet, I put my foot to the floor and right as it shifted from 3-4 popped the fuse and it died.

put in another and then it died about 11 minutes later.

put in another fuse and it popped 36 minutes later next fuse popped immediately upon start up. Next fuse died 4 min after, and then the fuse that’s in there now got me home.


conclusjon: I’m at a goddamn loss. I cannot make it do it no matter what wires I play with. It’s COMPLETELY random. I’m about 3 seconds away from yeeting it off a cliff. I paid $11k for the jeep as it’s on very nice axles and is very well built and is in very good shape with very low miles. For the love of all things holy… please help me.

 

Anyone? Anything) ?? Just leave a guy hanging? Everyone is on Facebook now and this forum is dead?

 

No not really dead, but people do leave due to all the arguing - Chrysler wire shields deteriorate and wires spill out and short intermittently and grounds often fail - Get a good shop manual. Page 12-2 in a Haynes Manual tells how to test for a short and it has wiring diagrams
The wiring harness snakes around and it's not always obvious. An electrical terminal cleaner is a good spray can to have too - Good Luck

 

You have a short between fuse 21 contact A-13 and the pcm, or ignition coil or any one of your 6 fuel injectors. Sadly no one can tell you where its at, but thats your issue, it will be hard to find if intermittent but it is there...thats why the fuse blows