Shifter doesn't move from park until I pump the breaks

[Eric H]

So after I start my Denali the shifter wont move from park. I figured out if I pump my breaks 10-15 times it will finally shift. Drives perfectly fine after that until i turn off the vehicle and then the same thing happens next time I try to drive it. I'm thinking it's the shifter lock switch (not sure if that's what it's called) but what would pumping the breaks do? Wouldn't it just not work if it was broken? This started happening after an incident where I had to slam on the breaks to avoid hitting someone in front of me who did the same. Any help would be appreciated.

2006 Yukon Denali

 

[SnowDrifter]

My first thought would be to locate the BTSI, visually inspect for any binding, check for power, then manually apply power to the thing to see if it moves freely

 

[swathdiver]

I think your master cylinder or something along those lines has had it. Not providing enough pressure at start up without assistance for some reason.

 

[jcjc]

Before diving in too deep, a simple thing to check is to look the brake lights to make sure the switch is working and has all the wiring in place. If you busted the switch or inadvertently kicked the wires in the panic stop this could account for it.

 

[Sam Harris]

Sounds like the brakes need some attention. All automatic transmission vehicles I know of within the last 25-30 years require brake pressure before shifting from park. Sounds like you have to build the pressure up before it is detected. I’d be figuring this out before driving it anywhere!