In 1998 2wd Grand Cherokee cruise control stopped working

cruise is last. the brains in the car dont allow this dangerous device to run, if things are bad. (even dead brake lights)
imagine cruise control out of control for a moment or with grand ma driving?
same with over-drive.
so what is wrong. well 1 simple answer
you failed to scan the PCM, and see those errors, causing those
symptoms.
scan it
get it scanned
win.

You either have a short or blown fuse

Check the vacuum hoses it is easy to notice if one is missing or not. If that doesn't work, I'd try the cruise control switch. Hope this helps

I press the control switch on my 1999 Jeep cherokee. the cruise light doesn't come on and the cruise does not engage. Please offer a solution.

Check fuses/relays and make sure they are all good; if so check the electrical wiring/connectors in the dash. Jeeps are notorious for loose wires in the dash.

Could be the plunger motor/ vaccum plunger under the hood. If the cruise light is on, the computer thinks it is working.

Ok, the '03 Jeep Grand Cherokee uses a small vacuum line to control the servos. Since your light comes on, it's obviously getting power. 9 out of 10 times it's the vacuum hose.
Pop the hood and look on the passenger side towards the back for the engine coolant reservoir. It's most likely underneath it so you may have to remove the res. Check the vacuum hose and all vac. connections then check the electrical connections. If that's not the problem, check the cruise control connection to the throttle linkage.
If that still doesn't do it, you may need use scan tools and diagnostic procedures that are out of the scope of home mechanics.
Wish ya luck!

check for power supplies and brake fluid level. if to low the cruise will not work.

Check your vacuum hose routing to the cruise control servo, it's a hard plastic hose and sometimes breaks. Does your vents work properly? An indication that you have a vacuum leak.

It is a vacuum leak under the hood. If it is a six cylinder, look on the driver side of the intake manifold for a L shaped fitting that usually pops off. If it is a V8 the leak may be near the battery.