Gas Cap

Hello! I'm also a fairly new member with a 1999 Tahoe LS 4x4 4dr. in great condition, although the miles are a little high, and the front pads need replacing,(of course)this is the greatest truck! My question is, I'm having a 420 service code, which I know this is the catalyst/sensor-of course it just failed state inspection for emissions and a bad Gas Cap! (doesn't hold pressure, I believe) What are the chances that I get a new gas cap and the 420 code corrects? There must be some relationship in the OBD system.
Any thoughts on this or do I have two seperate problems?
Thanks
John Mc

I've seen 2 different GM vehicles ('99 G. Prix, '04 TBlazer) that had a 'check engine' light come on that turned out to be the gas cap not sealing properly. Didn't get the exact code but I think your chances are decent you'll see the code go away with a new cap.

Update

Just an update--Replaced the cap, replaced the front pads and one sticking caliper. replaced ox sensor, that cleared the code. Good to go! Now-- New tires, Black wall or raised letter?? What was the 1999 originally
equipped with???? I know they are 245-75-16. My "99" is black.
Any thoughts??
Thanks
John
1999 LS