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resetting PCM?

M

mitsumotors

NAXJA Forum User
Location
Winnipeg
i looked at a couple of different threads and followed the steps. I unhooked the positive cable, held it on the a/c compressor for ground for 30 seconds, then with the cable still unhooked i turned the ignition to "on" then turned the headlights on then off then turned the ignition off then hooked the battery back up. then when i drove it i noticed that the clock still kept the time from before i did this. does that mean it didn't work?
 
what year?

dont know the exact procedure, but shouldnt you disconnect the negative battery cable and then cycle the key a few times.

for my 89, i disconnect both cables and touch them together and let sit for a few minutes. not sure if it does anything or not other than losing the clock and radio presets.
 
The reasons home computers keep time (and all bios information, even if unplugged) is because there is a small battery which keeps the bios running.

There should be no such battery in an XJ. Infact I've never even heard of an aftermarket head unit that had a built in battery for this purpose. I suppose that would be the only way it is possible, is through aftermarket.
 
just did it again to be sure. I pulled the positive cable, held it to the a/c compressor to ground it for 30 seconds, hooked it back up, turned the key on, turned lights on, then off, turned key off. still kept the time on the factory clock on the dash. what is the deal?
 
What kind of battery? You don't have an Optima with another lead coming out of one of the auxilary terminals on the side of the battery do you?

Probably not likely but I just thought I'd toss that out there!
 
Unbolt both cables, remove them from the battery post... Let them stay there without touching the battery.. Now turn on key, go have a beer.. After you have been gone for 15 min turn key off.. Now rehook battery cables..If you drank a beer to kill time do not drive your jeep..
 
I put a factory clock in my 95' and I noticed that when i disconnected my battery when I did my M.O.R.E plates, that it read the time when I first disconnected the battery :dunno: . Took me an hour and a half to do the job :cheers: .
 
mitsumotors said:
aftermarket radio, but its not the radio that is keeping the time, its the clock on the dash.
Click to expand...

OH are you talking about the small clock in that black space to the right of the gauge cluster and to the left of the radio?

That MAY have a small battery in it to keep the time! The newer XJ's do not have that auxilary clock, although you can add them in.

This is the clock you speak of which auto dims when you turn on your headlights, yes?
 
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