ok my Jeep has had this code since i bought it. The neutral safety switch had been bypassed by the dealership.(yes i know it is not safe that way. but it keeps me from having to buy one...lol) so if i clear the code with my obdii will it come back or will it stay gone forever?

never seen 1899 what is it for?

Trouble code P1899 means: Park/ Neutral switch stuck in park or gear. This is what i keep finding online. I tried to clear the code but it did nothing. came right back in less than a second.

Likely will not be able to clear it until the NSS switch is back in circuit.

I'd recommend you do so as it does more than just allow the vehicle to turn over; it controls your backup lights and also controls some transmission functions.

Try refurbishing it. Often restores full function.

http://go.jeep-xj.info/HowtoNSSrebuild.htm

http://bc4x4.com/tech/2010/jeep-neut...ty-switch-nss/

Like TJ said it wont go away if it's bypassed lol thats just c.s ,X2 on an attempt to refurbish.