New to me 05 Yukon has me scratching my head

[4Eyedturd]

I just picked up a 255k mile 05 Yukon that had been sitting for a few years and trying to make it a daily driver. I think the previous owner got tired of trying to figure it out and parked it. He said it would go into reduced engine power on the highway.

Since it had been sitting the fuel pump went bad but it came with a new “Ultra power” brand pump. With that pump installed and fresh gas it ran, kinda had a rough idle. I found a plug wire rubbing the steering shaft, fixed that with a new wire. Checked plugs and found a new set already in it. Chalked it up to maybe needing to have some fresh fuel ran thru it. It developed a P0332 while idling, so 2 new knock sensors and harness went in. I was expecting that to fix the previous owners problems.

So, no check engine light, but the ABS, TC and brake light are on which after changing the ABS module I found the rear end has been changed out at some point and doesn’t have the provision for the driver side ABS sensor so it’s zip tied up.I decided to test drive it. I had a problem with anything over say 1/4 throttle and seemed to die, while it was cutting out I gradually gave it more gas and it would come alive and take off. I could repeat it and it didn’t cause a check engine light for the brief 10min test drive.

I checked new fuel pressure and at idle is 70psi, verified with a separate gauge. Seems high and wrong. The rear not having the abs sensor has me questioning if it’s effecting how it moves and no codes makes me question if it’s the throttle pedal/throttle body. So I’m not sure how or where to start. I’m currently trying to find a rear end while I work thru the bugs.

 

[Scottydoggs]

pull any and all fuses related to the abs, then test drive. the rear sensors not seeing any activity, aka "wheel speed" might be making the pcm shut it down to prevent damage.

 

[Tonyrodz]

Also The Reduced Engine Power might be your plug going to your throttle body. It's a known common issue for the copper wire to break at this point. You can't tell because the outer wire insulation still looks fine.

 

[strutaeng]

Look up a wiring diagram for the throttle body (charm.li website will have it, along with diagnostics procedures), then backprobe at the ECU and the the throttle body and connect with temporary jumper cables. You are basically running an extra set of wires and an alternate path of electrical conductors. Drive it around and see if that does anything. If issue goes away, then you know where the problem lies.

 

[4Eyedturd]

Thanks for the quick replies. For the short time I’ve had it, the reduced engine power code hasn’t popped up. I went ahead and tried another throttlebody I had laying around just to see if it made a difference. It seemed to not hiccup at 1/4 throttle but still did it at 3/4. The more I drove it around the better it got. Maybe sitting for 2 years didn’t do it any favors. I put a few miles on it around the neighborhood and it got way better. Added some fresh 93 gas and it hasn’t hiccuped. It did pop a P1810 code so I’m gonna change the trans filter and fluid and see if it helps. I also managed to find a good rear end with the abs sensors so it’ll go in soon.

 

[4Eyedturd]

Short update, the new transmission pressure module seems to have fixed my bucking/almost dieing symptom. I’ve been daily driving it for a little over a week and it’s been great. The correct rear end solved the ABS and stabilitrack lights. 2 new knock sensors and harness didn’t fix the P0332 code. Ive got a rattle from the front suspension that needs addressing soon but besides that its a great car, and I’m glad to be back in a GMT800, best cars ever made