Automatic Truck Wont shift from Park

1998 GMC YUKON
187,000 MILES • V8 • 4WD • AUTOMATIC
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STPHNHRRLL
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Yesterday my Vacuum booster went out and I replaced it. The brakes work great, but now the car doesn't want to go out of park. Sometimes it will but usually it wont. I have a mechanically inclined friend who said that I may have pinched the gear cable, but I checked it and the cable is fine. I need to know what is wrong, & what part will fix it.

Thanks
Aug 21, 2011 at 6:52 AM
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RASMATAZ
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Check and test the shift interlock control system shift control soleniod
Aug 21, 2011 at 6:56 AM
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STPHNHRRLL
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How do I do that?
Aug 21, 2011 at 7:01 AM
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WRENCHTECH
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That would be called the shift interlock feature. It operates on the same circuit as the brake lights so the first thing you want to do is to make sure the brake lights are working when this problem is present. If the brake lights are working, that proves the circuit is good up to that point, then you'll have to get to the solenoid in the console/column. Disassemble as much as you have to to access the solenoid near the shifting mechanism. Us a 12v test light to test for power coming and going at the solenoid when the brake is applied. If power is arriving and switching and the solenoid is not triggering, the solenoid is bad and will have to be replaced.
Aug 21, 2011 at 1:02 PM