Got "Goofed" on a 2007 Yukon XL SLT 2500 4x4

[Jakeo1962]

After selling my 98 GMC 2500 Sierra Ext Cab 4x4 7.4 Vortec (454) pick up with 190+ miles that I ordered in 97, I found what I thought was a great deal, 2007 Yukon 2500 4x4 with 145k. got sc@ewed is more like it.
Started off by seeing PO hanging 4 sale sign, I stopped, took a short test drive because PO had obligations, I drove it about 3 miles and only about 45 mph. Guy seemed honest was prominent in the area so I trusted....BAD MOVE!. Purchased drove home following day and couldn't go over 50mph or it would backfire and just not run. I called immediately but he stated he was busy but first question was"".IS CHECK ENGINE LIGHT ON?"" I stated wanted my $ back but no ,he said to take it to mechanic, he would pay. Got it to shop getting 6 mpg and told mech all. Called me asking where I got and then told me it was throwing codes like he's never seen and would cost me big $ to repair BUT wanted me to contact PO, I did. PO told mechanic a story and then asked PO why the CHECK ENGINE LIGHT BULB was DRILLED OUT? I guess PO stuttered and said he had no idea BUT mechanic asked enough to know who did it.
I got PO on phone telling him I wanted to be paid for repairs and he told me to take it to a "backwoods" mechanic and not the priciest mech in town. I threatened and he said he would pay.
Mech replaced 2 catalytic converters and said it ran fine but alot of wiring issues. I payed mech, drove it and noticed terrible screeching from sound system, climate controls screwed up, no back up cam, much more but truck runs fine.
Sent PO a bill and he sent me nasty letter and $1k...final. (I'm still dealing with that)
Question is the screeching is whether stereo is on or off, happens when fasten seat belts, hit bumps, driving me nuts. Many other wiring issues but I did tow my 5kboat and didnt even know it was back there. Thats main reason I bought. It gets 12-14 mpg on highway, all 4x4 works as it should but the screeching makes it a pain to drive.
SORRY for long post but for a first I wanted all to know background because I know I will be back on here.

 

[Amaster]

Do the turn single sounds work? Cause if not then someone messed with wiring going to your stereo.

 

[Fless]

Not judging but this is all the more reason, after a thorough test drive, to have a pre-purchase inspection done by the mechanic of your choice (unless, of course, you're very familiar with the vehicle you're looking at and you feel comfortable with your own inspection). Hopefully that's a mechanic you trust and have a relationship with. I find it money well spent, and I've walked away a few times due to the results. If nothing else the results can be a negotiating tool. If the seller won't take it to have it inspected by your shop, walk away.

 

[OR VietVet]

Check all grounds. https://www.fixmyoldride.com/Chevro...e7e5cd24ed24635&at_ab=per-2&at_pos=3&at_tot=4

 

[swathdiver]

After selling my 98 GMC 2500 Sierra Ext Cab 4x4 7.4 Vortec (454) pick up with 190+ miles that I ordered in 97, I found what I thought was a great deal, 2007 Yukon 2500 4x4 with 145k. got sc@ewed is more like it.
Started off by seeing PO hanging 4 sale sign, I stopped, took a short test drive because PO had obligations, I drove it about 3 miles and only about 45 mph. Guy seemed honest was prominent in the area so I trusted....BAD MOVE!. Purchased drove home following day and couldn't go over 50mph or it would backfire and just not run. I called immediately but he stated he was busy but first question was"".IS CHECK ENGINE LIGHT ON?"" I stated wanted my $ back but no ,he said to take it to mechanic, he would pay. Got it to shop getting 6 mpg and told mech all. Called me asking where I got and then told me it was throwing codes like he's never seen and would cost me big $ to repair BUT wanted me to contact PO, I did. PO told mechanic a story and then asked PO why the CHECK ENGINE LIGHT BULB was DRILLED OUT? I guess PO stuttered and said he had no idea BUT mechanic asked enough to know who did it.
I got PO on phone telling him I wanted to be paid for repairs and he told me to take it to a "backwoods" mechanic and not the priciest mech in town. I threatened and he said he would pay.
Mech replaced 2 catalytic converters and said it ran fine but alot of wiring issues. I payed mech, drove it and noticed terrible screeching from sound system, climate controls screwed up, no back up cam, much more but truck runs fine.
Sent PO a bill and he sent me nasty letter and $1k...final. (I'm still dealing with that)
Question is the screeching is whether stereo is on or off, happens when fasten seat belts, hit bumps, driving me nuts. Many other wiring issues but I did tow my 5kboat and didnt even know it was back there. Thats main reason I bought. It gets 12-14 mpg on highway, all 4x4 works as it should but the screeching makes it a pain to drive.
SORRY for long post but for a first I wanted all to know background because I know I will be back on here.
View attachment 356486

Jake, if you like and are going to keep this truck buy a Tech-2 so you can properly, quickly, diagnose and fix it.

She looks leveled with fender flares. Flares are often used to cover up rust. Check your RPO codes in the glove box, Look for GT4 or GT5. GT4 is 3.73 gears and means your maximum tow rating is 7500 pounds, GT5 is 4.10 gears and means your max tow rating is 9500 pounds. Trucks this age often need a few $$$ in repairs to get them back to normal. Highway mileage seems about normal for a 4-speed equipped 2500.

There's a couple guys on here with these beasts.

 

[Jakeo1962]

Thank you ALL for the fast and helpful replies.
Yes turn signals all work and I have put about 3k miles on since I bought. I will check grounds soon (Getting heated warehouse for Winter projects) as I plan on removing stereo and having replaced with a new unit, I'm paying someone.....LOL
I plan on keeping this as it is a nice vehicle in today's market and I have had people want it because it looks as good as it do's. The under carraige and frame is surprising clean for a truck this age. There are spots of rust but honestly not as bad as my 98 was, I know it's a GMC thing but I still keep buying them.
My nephew is moving here and promised that this truck will be like new by Spring (He's a certified mechanic from Minnesota) but I like to ask people who own them and love the help I have seen on this site.
THANK YOU ALL.

 

[Trey Hardy]

Whenever I test drive something I dog it hard I run the shit out of it if something is going to happen it’ll happen right then if it holds and drives good everything checks out then I get it I’m still driving my 300,000 mile Tahoe Dailey I baby it but when I went to buy it the dude said I was trying to kill him lol

 

[Jakeo1962]

Major mistake on my part as far as the test drive but I "trusted" the guy as I was brought up to do if someone has good credentials. That part I will admit I was DUMB!
I've bought and sold many trucks and boats and Yes normally if I don't know the person or if I don't know anything about the vehicle, I drive it like I stole it..LOL
Now we have put a total of 5k on it and besides the screeching of the stereo and inaccurate fuel gauge, we love it. The next purchase is a "Bull guard" for the front end. The deer in this area are scarry and I don't want all GMC's beautiful(BS) plastic-fiberglass broken up when one decides to run in front of me.

 

[Jakeo1962]

TYVM

 

[dnt1010]

If the truck has the rear entertainment and has a radio screech it is most likely the rear control head unit that needs replacement. Next time it is screeching reach back and press on the face of the rear control unit and see if it stops. They are around 100 bones on amazon. I drove wit a screech for almpst a year before figuring it out. GM placed the unit in harms way if the button is hit pretty hard or if say a childs backpack strap hangs on a knob and breaks it off (YUP THAT WAS MINE) it destroys the head unit internals......