I discovered on the JeepForum that there was a police package available on the XJ. It included an Extended Idle switch on the dash. When that switch was engaged it grounded a wire that went to the PCM which raised the idle to 1000rpm in P or N. It did that to improve cooling and alternator charging under severe conditions like flashing lights being on for long periods. But what a maintenance tool to be able to let the computer raise the idle without setting a code that the desired idle was not being met. So I learned that the solid grey wire at PCM connector terminal A-12 is the one. It is in the factory harness but dead-ends at another connector if you don't have the police package. So I just opened the harness where there was more room and separated that grey wire. I cut it and soldered a wire to that and then made a ground wire too. I sealed and shrink-wrapped all that and tucked it all back into the harness. Now I need to run that wire through the fire wall. Then locate a small toggle switch and install it on the dash. This is all I got done before it got dark and cold out.