01 Yukon wont stay broke long enough to fix

[1slo4.8]

try leavin the pressure gauge on there for a while to see if it drops? or maybe you've already done that

[1BADC10]

Any chance that key has a chip in it that has lost it's link with the 'Kon?

A lost association will yield what you're talking about. I only say this b/c you said you switched keys, and it started right up. Has it always happened ONLY when using her keys, or both?

Just another angle to look into.

[ff_jeff]

Any chance that key has a chip in it that has lost it's link with the 'Kon?

A lost association will yield what you're talking about. I only say this b/c you said you switched keys, and it started right up. Has it always happened ONLY when using her keys, or both?

Just another angle to look into.

thats why i sent him the links for the vats eliminator, it is that.

[1BADC10]

thats why i sent him the links for the vats eliminator, it is that.

But why not have the dealership quote a reprogram price... worst they can tell you is it'll cost ya $40 to reprogram (if that's really the issue).

I'd be curious as to how the bypass kit works, and what's the downside to using it. Sounds like this is to eliminate VATS all together. I wouldn't do that to mine, but to each his/her own.

[86 Silverado LS1]

Any chance that key has a chip in it that has lost it's link with the 'Kon?

A lost association will yield what you're talking about. I only say this b/c you said you switched keys, and it started right up. Has it always happened ONLY when using her keys, or both?

Just another angle to look into.

I'm not sure. That isnt something I have paid attention to before now. It may have been a coincidence that it cranked with the other key but I dont think so. I have done some searching and heres what I have found so far:
The main possibilities are: 1. Bad lock cylinder. 2. Bad ignition switch. 3. Bad IPC. 4. Bad ECM. 5. Wiring problem to either of these components.
Im still not sure about the security system. How does this thing work? What triggers it?