The 1999+ is nothing like your 1996. 1999+ do have heater blend door issue, but
using advice from a 1999 is like repairing your 1996 using a GMC Jimmy manual.
Now with that said, on a 1996 Mil code 23 translates to OBD2 codes P0112 & P0113 both of the codes point to the same problem "air intake temp too high or low".
QUOTE=adamsetzler]According to the error code list, yes, but the person with the 1999+ Jeep heater fix (jeepheaterfix at yahoo.com) said that a loose vacuum line on an older model could be causing my problem.
What do you know?

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His, 96 Limited, 5.2 Magnum, Magnaflow CatBack System, HID Head & Fog Lamps, 242 T-case swapped , Rear Trac-Loc. Chrome grill added to match the wheels.

Hers, 96 Limited I6, 242 T-case, HID Head & Fog Lamps.