2004 GMC Yukon XL1500 electrical issues

[flyingdakota1]

Hey Y'all!
So, we just recently rebuilt and installed the 5.3L L59 in my wife's Yukon. I have been driving it to break it in and make sure there were no issues before she started to drive it again.
This last week it has been randomly cycling the locks, door chiming, "Passenger door Ajar" after putting it in gear (actually when you pull back on the shifting lever is when it starts) Also, the "Pass lock" and "Brake" lights are DIMMLY lit up and remain on even with the key out and engine off. The brake light has faded completely out a couple times but the passlock light remains on.

The door lock thing is so annoying! It will do it maybe once or twice....the 10 minutes later cycle MULTIPLE times and sometimes it won't stop at all. If I open the drivers door in motion it stops. But then as soon as I close it, it starts up again.

And not sure it this has anything associated with it but once the engine was in and we were starting to drive it the idle has been rough and it pops a P0300 (random misfiring) I have since replaced the B1 and B2 O2 sensors, which has seemed to help but still has a rough idle.

Any help or input is greatly appreciated!
TIA
Tim

 

[strutaeng]

Sounds like multiple issues. Maybe an issue with Body Control Module (BCM)?

I "think" the door switch module is the one associated with unlocking the doors via the key fob? Try unplugging that and see if that issue stops.

On the misfire, it would be better if you hooked up a scanner that gave you cylinder-specific misfire. A lot of the generic code readers don't do that and it's really difficult to guess why cylinder may be misfiring. I bought the TopDon dongle ($60 on Amazon black Friday) that works with your phone and was surprised how much bi-directional functionality it has over my "high-priced" Innova has, which was much more money when I bought it a couple years ago.

 

[iamdub]

Hey Y'all!
So, we just recently rebuilt and installed the 5.3L L59 in my wife's Yukon. I have been driving it to break it in and make sure there were no issues before she started to drive it again.
This last week it has been randomly cycling the locks, door chiming, "Passenger door Ajar" after putting it in gear (actually when you pull back on the shifting lever is when it starts) Also, the "Pass lock" and "Brake" lights are DIMMLY lit up and remain on even with the key out and engine off. The brake light has faded completely out a couple times but the passlock light remains on.

The door lock thing is so annoying! It will do it maybe once or twice....the 10 minutes later cycle MULTIPLE times and sometimes it won't stop at all. If I open the drivers door in motion it stops. But then as soon as I close it, it starts up again.

And not sure it this has anything associated with it but once the engine was in and we were starting to drive it the idle has been rough and it pops a P0300 (random misfiring) I have since replaced the B1 and B2 O2 sensors, which has seemed to help but still has a rough idle.

Any help or input is greatly appreciated!
TIA
Tim

I'd double-check all wiring surrounding the engine. Could be a loose ground or wire harness pinched or misrouted and cut, causing intermittent shorting. The computers in these things, especially the BCM, does weird stuff with excessive voltage fluctuations, shorts and/or power losses. Start at the battery- how's that main ground that goes to the stud on the front end of the passenger cylinder head? The ground for the ignition coils on that bank of the engine is there, too.

 

[flyingdakota1]

So I do have the Topdan ArtiDiag500 and it seems pretty capable for the codes.....Does live data too...only thing it doesn't access the BCM that I can tell. Still learning it.
The wiring I was pretty careful with and made sure the grounds were clean and all had good connections and back where they needed to be. Tried to be careful with the harness and make sure we got the harness back in place.

Where is the BCM located?

and is there an affordable Scan tool that will read the BCM?

TIA
Tim

 

[iamdub]

So I do have the Topdan ArtiDiag500 and it seems pretty capable for the codes.....Does live data too...only thing it doesn't access the BCM that I can tell. Still learning it.
The wiring I was pretty careful with and made sure the grounds were clean and all had good connections and back where they needed to be. Tried to be careful with the harness and make sure we got the harness back in place.

Where is the BCM located?

and is there an affordable Scan tool that will read the BCM?

TIA
Tim

I'm not the one to have any recommendations for such scanners. But, you still have some free preliminary troubleshooting to do. With it idling, have the windows down and pop the hood. Shake and tug test all the wiring, starting at the battery. I wouldn't worry with the engine sensor harnesses. But you have the PCM, the large one going through the firewall, down to the transmission, etc. Hell, the battery itself could have an intermittently open or shorting cell. Was the engine out for a long time? Did the battery die while it sat? You might have been careful with the wiring you handled, but you still disconnected and reconnected plugs and one could have been weakly pinned from the factory. Is it possible that rodents could have chewed wiring while it sat?

The BCM is up in the dash, behind the knee bolster, above the brake pedal.

 

[flyingdakota1]

Ok, I'll try that....we pulled the engine on the 9th of September and had the other one in and running end of November. Battery was out and I kept it charged. Alternator has been working good too. (14.3Volts running) and it was in the driveway with no evidence of rodents, we are mostly "in town" and typically don't have any of those issues.
I'll check the harness as you suggest tomorrow.

 

[iamdub]

Ok, I'll try that....we pulled the engine on the 9th of September and had the other one in and running end of November. Battery was out and I kept it charged. Alternator has been working good too. (14.3Volts running) and it was in the driveway with no evidence of rodents, we are mostly "in town" and typically don't have any of those issues.
I'll check the harness as you suggest tomorrow.

Gotcha. Just trying to cover all the bases.

 

[S33k3r]

For now, I'd suggest going into the DIC and disabling the auto locking features, and maybe some of the other automatic options. That should bandaid it until you can really tear into things.

 

[flyingdakota1]

Thanks! I did think of that later....I turned it off and it hasn't done it since. With a friends scanner I noticed there was a rear wheel speed sensor that had erratic voltage, so I am wondering if that has anything to do with it?

Also, Friday I went to another friend shop and he did and CPS relearn and a short fuel trim reset and that has seemed to help some. But the one thing that was really noticeable was that when he commanded the idle to be at 725 RPM, actual Idle was 675ish and all the misfires went away and everything was nice and smooth. So, now I need to figure out how to permanently set the idle speed a little higher...

 

[Marky Dissod]

I would not only check and clean every single electrical ground, I'd even consider ADDING electrical grounds.
Tahoe PPVs & SSVs will show you where you can safely add electrical grounds.