I recently purchased a 2005 Bonneville GXP from a friend, who kindly explained everything he knew to be wrong with it. I fixed most of the little issues already. He told me it had a bad o2 sensor, and that's why the Service Engine Light was on, I took it to Autozone today, had them run their OBD2 tool, and came up with this:

P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)
P0455 Evaporative Emission System Leak Detected (gross leak/no flow)
P0442 Evaporative Emission System Leak Detected (small leak)
P0442 Evaporative Emission System Leak Detected (small leak)
P0741 TCC System Stuck Off - Mechanical (4T65-E)

*Yes, there was two of the exact same P0442 code on the scan, though I'm not sure why?

1. First question is, would/could all those EVAP leaks be related to each other, as well as the Lean Bank codes?
I pulled the beauty cover, looked around, shot some carb cleaner st every hose I could, and didnt notice an idle change at all. Gas cap seems tight. It's possible some sort of fuel tank exhaust line is broken, as there is a line under the carpet in the trunk that appears broken, I'll have to get a picture of it, but not sure if it could cause all those codes?

2. The TCC code kind of confuses me, as I was under the impression that the Northstar GXP cars came with a 4T80, not a 65? My build sheet (I emailed GM and got the original build sheet) has a code of MH1 and MX0 for transmission, but doesnt specify from what I can find, which it has. Also, there is no drivability issues whatsoever with the transmission. It shifts fine, the traction control turns on and off, and seems to be working as intended, and there are no lights that come up when flooring it and slipping, so I'm not sure if that's an erroneous code or not?

Mostly I'm just unsure of where to start with the vacuum leak codes? Any help anyone could provide, would be greatly appreciated!

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2005 Pontiac Bonneville GXP
White Gold TriCoat

P0171 (and 174)

bonneville-gxp-northstar-powered-cars/topic30881.html?hilit=p0171

P0455 and 442 answered at a high level here;

post447739.html?hilit=p0455#p447739

P0741

bonneville-gxp-northstar-powered-cars/topic51329.html?hilit=p0741

1) EVAP codes can work in tandem and yes it could drive the lean codes.
2) The code is a generic titled GM code and can flag if the fault is there regardless of actual transmission as both most likely use the same base program table.

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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

Thank you for the links! I had already read through the 741 one for transmission, and the 442 one, but hadn't seen the 174 one. I did take a picture of the line I had a question about, that's in the trunk. I hooked it back up, after work I can run it again and see if it makes a difference. I just gotta figure out how to post a picture to show the line I'm talking about, I'm sure you could tell me exactly what for.

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2005 Pontiac Bonneville GXP
White Gold TriCoat

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2005 Pontiac Bonneville GXP
White Gold TriCoat

That is a rear sunroof drain and will not cause any of your DTC's. Of course it will cause you other water leak related problems. You can simply use something like a wire tie/tie-wrap to fix it. If necessary, there is also information on the numerous water leaks these cars suffer and how to fix them (including the sunroof drains - most notably the front drains).

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Bose Luxury Sound System w/Touch Screen Navigation, Addition of Factory XM, 2005 MY Antenna, OnStar Upgrade (3G),
RainSense Wipers, Backup Camera, '00 Style Door Panel Courtesy Lights, Heated Washer Solvent, 2X Remote Trunk Release,
Turn Signal Mirrors, Center Console Courtesy Lamp, Rear Outboard Heated Seats, PVD Chrome 18" Factory Rims, Upgraded
Carbon Fibre Appearance Interior Trim, Highly Modified Main Body Harness, Instrument Panel, Door, Door Panel & Headliner
Wiring Harnesses, Custom Fuse Box & Tire and Loading Information Decals, Additional Acoustic Insulation

Thank you for clarifying what that line was! I was hoping it was something to do with the EVAP codes, but I guess I'll do some more digging to try and find the problem.

I was browsing these forums when I first started looking at buying this car, and was impressed at the knowledge you all have. I am happy for the internet and places like this! Hopefully I can contribute something someday!

Speaking of which: I'm not sure if I found it on this forum, or somewhere else, but if you email socialmedia@gm.com they will gladly send you an original build sheet, with RPO codes. I asked about production numbers, but they dont have that info. In either case, if that info isnt somewhere on this forum, let me know and I'll make a new thread, or a mod could put it somewhere so others could find it.

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2005 Pontiac Bonneville GXP
White Gold TriCoat