This seems to be an issue that's starting to pop up on older XLRs. Just had it on mine as well. Here are two ways to tell if the shift lock solenoid is working:
Without a Tech 2:
1) Start the vehicle.
2) With your hand on the shift lever, press the brake pedal.
3) Listen for an audible click coming from the base of the shift lever each time you depress the brake pedal.
4) You should also be able to feel the solenoid lever throw through the shift lever.
Don't get crazy with pulling back hard on the shift lever, you'll only raise your blood pressure and possibly break something more expensive. Keep pumping the brake pedal to signal the solenoid to move.
With a Tech 2:
1) Connect the Tech 2 and start the vehicle.
2) Navigate to the Y Body menus.
3) Select F6: Transmission/Transaxel; select Shift Lock Control<rcdlr<f1 p="" data.<="" data="" display<f0="" rcdlr<f0="">
4) There are two status readings on the bottom of the display: Data: Shift Lock Solenoid Comm and Data:Shift Lock Solenoid Status. Both should indicate "Locked" without the brake pedal depressed and "Unlocked" when the brake pedal is depressed.
If you don't feel (or hear) the solenoid actuate, or the status doesn't change on the Tech 2, remove the center console cover plate by slipping the shift lever trim ring down and loosening the T-15 Torx screw securing the shift knob to the shift lever.
Remove the shift knob and pry the console cover off by pulling up on the back and then the front to disengage all four clips. Lift the cover up and slide it over to the left side of the centerline "hump."
The Shift Lock Solenoid is the square component with a rear-facing shaft, sitting to the right of the base of the shift lever. Depress the brake pedal a couple of times to visually verify the solenoid isn't operating. If it isn't, jiggle the wires that come out of and run adjacent to the solenoid, while holding the brake pedal down. The harness in my car had a splice in it that when jiggled, allowed the solenoid to engage, so it was easy to fix. Maybe the guy missed school on the day when splices were taught.
You can manually move the solenoid lever to see how it allows the shift lever to slide back by moving a little white plastic lock out of the way. In a pinch, you can hold this in place to get the car out of Park, then drive it in for repairs.
I'm surprised that there have been so many reports of this problem lately. Solenoids are pretty bullet-proof. They're just electromagnets and need power and a ground path to complete the circuit throwing the lever. In the XLR, the brake pedal switch completes the ground path by signaling the RCDLR. (The reason for the "Comm status" on the Tech 2.)
In a nutshell, there are four main failure areas for this problem: The brake pedal activated switch, the RCDLR which applies the ground to the shift lock solenoid when the brake switch is depressed, the shift lock solenoid, and the associated wiring. There's a mechanical linkage cable from the shift lock solenoid assembly to the tranny that engages the transmission too.
Hopefully this might help someone else with a similar problem.
CC

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