CY, if it has it, the check engine light will blink a number of times for the code or codes.
Code 13 will show up as the light comming on once then pause and then comming on three times quickly.
If you got it, be ready to write the code(s) down. We got the numbers if it works.

You can try it and see. I know my 97 did, and some of the 99's did as well. It only takes a minute to try and see. The main thing to watch for is the check engine light to flash, but the odometer should also give a digital read-out of the actual number if it will do it. I know on the trucks 99 was hit or miss wether it would do it or not. So your WRANGLER may be able to.

so ON and OFF....wait two seconds....on and off.....2 seconds.....on and off.....2 seconds......on then see if the check engine light blinks and look for a code number on the odometer??? think i got it.....give me 5 minutes and i will be back.....

well just tried it several ways 3 ons and then 4 ons, and no luck.....

did i do it right? do i have to start it or just turn the key on and off?

If that don't work, do it all within 5 seconds.
The book on the Caravan says 1989-95 just turn the key on but it was published in 1996 and may include newer models.
By the way, you're not cranking it up, just turning it on till the dash lights come on.

will my owner's manual tell me how to do it? or are you looking at a repair manual?

Either 3 on's within 5 seconds or just turn the key on.
If nothing then you may need a code reader.

Repair manual.
FERM, get back here!!

looks like FERM is gone...... tried the on off thing several ways and no luck. wish we had an autozone close. all i have is a advance auto. and several of the local repair shops i use said at least $65 to plug her in.

Go with the ON-OFF-ON-OFF-ON-OFF-ON. Make sure you go to run and then back to off, and do not start it. If you bump it to start you have to start over. But the cycling needs to be smooth, if you have any breaks in it it will not go into self diag. Just go through them smooth and steady and see if that works. If not then yours may not be capable of it. Not all the 99's will do it. AUTOZONE is still free, or you can pick up a cheap OBDII code reader at WAL-MART for under $50.