Step back a bit. Either a) the GP light is coming on and you are not noticing it (doubtful as you are aware it comes on briefly), b) the GP light is burned out but the GPs are working fine, or c) GP light is burned out but GPs are NOT working fine.
Ignore a)
For b) invoke the bulb/gauge test by holding the trip odometer button down while turning the ignition which will cycle all the lights and gauges. If GP bulb is good it should light. If not go to
http://colorado4wheel.com/manuals/Jeep/KJ/ and download my tech tips PDF. In bookmarks go to Instrument cluster removal and bulb replacement - includes LED bulb replacement for how to replace GP light LED.
For c) if the GPs are not working right Flash is correct that will throw a CEL/code but if your MAF is unplugged you won't be able to "see" the problem via the CEL because it's always on. Choices a) plug MAF back in and drive for say 5 days for enough engine cycles to turn off CEL caused by MAF, if CEL does not go off you probably have a GP problem or b) possibly check for current at key on to GPs with volt/ohm meter, I'll leave to others how to do that check or c) get the code reader Flash mentions or find a shop with a DCJ code reader or equivalent (not just any old reader will do) to check for codes other than MAF.
NOTE - for those that disconnect the MAF it's not a good idea to do so unless you also load a free ECU flash that will disable the MAF CEL. The obvious problem of driving around with the CEL on all the time due to the MAF being unplug is as noted you cannot see the CEL come on for other reasons.
PS as WWdiesel notes below my memory or his may be off re. DIY tunes and MAF light but as he says let's see what Marco says.