Juh Juh Jinx

Got a check engine light... use a code reader and it says "Leak detection pump or mechanical failure" not sure what it means... help?

ol"blue

Sounds like an issue with the Fuel Evaporation Control System (EVAP). Some have a pump that checks the system for leaks on start-up. The system consists of vacuum lines between the fuel tank vent line, the EVAP solenoid and/or motor, and the charcoal cannister where the vapors are stored while the vehicle is not running. The vapors are then drawn into the combustion chamber through the intake manifold to be burned.
Check the vacuum lines first, including under the rear near the fuel tank. The vapor line runs alongside the fuel sending and return lines. It has sections of rubber connected to steel lines in the rear. It sometimes becomes brittle and cracks causing leaks.

tjwalker

Post the EXACT code here for the most accurate replies.

And also perform a google search. Search for the code + Jeep Cherokee

For example, use a search string of P0743 + Jeep Cherokee

You will get very good information using these searches.