If the light is still coming on, it's could a bad sensor in the oil pan but there was also a TSB on the subject that indicates increased oil capacity and a new dipstick.
Here is the TSB
Oil Level Sensor Light - Comes On Prematurely
Oct. 19, 1992
Oil Level Sensor Light
THIS BULLETIN APPLIES TO VEHICLES BUILT PRIOR TO MDH 08-22-XX AND EQUIPPED WITH A 5.2L ENGINE AND A VEHICLE INFORMATION CENTER (VIC).
1993 (ZJ) Grand Cherokee
The oil level light in the VIC may remain on with the oil level 1/4" below the full mark.
If the oil level light comes on prematurely, add one pint of oil. If the light turns off perform the following repair procedure, and advise the customer of the increased oil capacity.
Label package 4740967
This bulletin involves increasing the oil capacity of the engine to 5.5 quarts.
1. Remove and discard the dipstick and replace it with the part number 4740796.
2. Add oil to bring the level to the full mark on the new dipstick.
3. Apply the oil capacity label on the radiator shroud as close to the dipstick as possible. Make sure that the label is in clear view.
4. Affix the appropriate labels to Page 4-16 and to the rear inside cover of the owners manual.
Reimbursable within the provisions of the warranty.
Tuesday, February 8th, 2011 AT 12:56 PM