One problem related to ignition module has been reported for the 1999 Jeep Wrangler. The most recently reported issues are listed below.
The check engine light keeps coming on. I have returned it for service 4 times, and need to bring it back in again. First they said it was a solenoid. Then they traced all of the wiring. The time after that they replaced the module. Next they replaced all of the spark plugs (recall service). They replaced the spark plugs 2-3 weeks ago, and the check engine light is already back on. The dealership's service has been good, but they nor Chrysler seem to know why this is occurring.