Jump mistake now crank no start
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Joined: Oct 2016
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Model: Cherokee
Jump mistake now crank no start
It was very dark out this morning and I made the mistake of crossing jumper cable wires on my 99 Grand Cherokee. (The Cherokee has the bad battery.)
I was able to jump it yesterday afternoon. When I try to start it after the mishap I get a crank, no start situation. All lights work fine but I noticed the fuel gauge and battery gauge are not doing anything.
Can I please get a productive recommendation of things to troubleshoot such as fuses or whatnot? Anything serious and this bad boy is going to the scrap heap as I am sure that it is cursed.
Thank you so very much.
I was able to jump it yesterday afternoon. When I try to start it after the mishap I get a crank, no start situation. All lights work fine but I noticed the fuel gauge and battery gauge are not doing anything.
Can I please get a productive recommendation of things to troubleshoot such as fuses or whatnot? Anything serious and this bad boy is going to the scrap heap as I am sure that it is cursed.
Thank you so very much.
Old fart with a wrench
Joined: Nov 2010
Posts: 14,398
Likes: 741
From: Manlius, east of Syracuse, NY
Year: 2000 XJ Sport & WJ Laredo
Model: Grand Cherokee (WJ)
Engine: 4.0L
My recommendation is to take the PCM to someone and get the power supply tested. There's an internal power supply stage for the 5 volts for the electronics. You may have damaged it with the reverse polarity or triggered a fail-safe function.
CF Veteran
Joined: Jan 2012
Posts: 2,208
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From: Ocean County, NJ
Year: 1998
Model: Cherokee
Engine: 4.0L
My question would be, how long/how many times did you crank it with reversed polarity? More than likely, like Dave said, the PCM is how I like my bacon..... crispyyyyy
Senior Member
Joined: Mar 2010
Posts: 855
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From: Southern California
Year: 1989 Laredo
Model: Cherokee
Engine: 4.0 Inline 6 Renix
CF Veteran
Joined: Nov 2015
Posts: 2,863
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From: syracuse ny
Year: 1997 230,000 miles
Model: Grand Cherokee (ZJ)
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
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Senior Member
Joined: Feb 2012
Posts: 884
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From: Baltimore
Year: 2002
Model: Grand Cherokee
Engine: 4.0L (AMC) Straight Six
I accidentally fried my '94 ZJ's PCM by doing that, and blew all of the fuses and relays... gotta be careful about what you're doing, you most likely fried your PCM. 
CF Veteran
Joined: Nov 2008
Posts: 7,874
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From: Northern Ontario, Canada
Year: 1990, 1999, 2000
Model: Cherokee
Engine: 4.0
yep, the guy that did that at my shop, used my new TJ to jump his 95 xj. at least he hooked the cables up properly on my TJ. not that it matters, but my jeep still ok. this was many years ago.
it fried his pcm, and blew his buss fuse for his alternator.
you could tell where it blew in his pcm when you take the cover off. it was like toasted jelly and stunk like melted crap.
and yeah, you're lucky the battery held up.
it fried his pcm, and blew his buss fuse for his alternator.
you could tell where it blew in his pcm when you take the cover off. it was like toasted jelly and stunk like melted crap.
and yeah, you're lucky the battery held up.