2007 Yukon Denali Xl - Power Loss - No Start - Help!

[07 Denali Xl]

OK, so my wife goes to leave school with kids and the Denali wouldn't start. For about a week I noticed when cranked the headlights were pulsating or flickering with the engine speed. Another night I then noticed the interior lights, dash, instruct, overhead all pulsating.

So when I get there I think it the alternator has been failing. I go get one and change it out. All this time I have the battery on charge. Before I started with new alternator I took battery to be tested. It was fully charged and good had 800+ amps. I went back hooked back up. Tried to crank. Nothing. No click, no turn over. Checked all fuses nothing blown. When turning key fuel pump comes on, radio works, info taiment comes on, headlights work, power seats work, horn works, power windows work. Butttttt, what doesn't work is this... interior lights do not come on, power locks do not work, keyfob to lock does not work, brake lights do not work, rear lift gate doesn't work. My dad is a retired mechanic, he tested fuse panels with light tester for these accessories and I think half lot up some didn't. Nothing burnt. Power coming in to everything. Also when pressing keyfob the locks didn't work but the bscklights of the center dash would light up. So it is reading the keyfob. It's still sitting at the school as I'm trying to avoid the dealer ship as I know their trouble shooting will result in over $1000 in fess before they even possibly figure it out. Thinking "bcm", def electrical, but I'm looking for anyone who has experienced this....

 

[#1taho]

I am not familiar with this model truck and electrical but how's the starter relay and the ignition wire going to the starter. I have read somewhere about the relay. You can switch it with another one in the fuse panel for testing and replace later if that's the problem

 

[07 Denali Xl]

I am not familiar with this model truck and electrical but how's the starter relay and the ignition wire going to the starter. I have read somewhere about the relay. You can switch it with another one in the fuse panel for testing and replace later if that's the problem

I switched some around but I think my dad tested those. But how does that explain all of the power losses to certain components? This vehicle does have remote start as well. Haven't towed it yet and its to low to get under it in the parking lot it's at.

 

[#1taho]

My thought was they use power from one system to feed another.
Have you cleaned the power and grounds. They are a problem on all these trucks. I wish I could help you more but haven't had to do much work on your year truck.
If it has remote start I would go over all the conections. Guys who install them are hacks 90% of the time. Could be a loose wire or bad control box. Now I am grabbing at straws.

 

[#1taho]

Have tried jumping power across the starter? Just see if it's a starter or ignition switch ?

 

[07 Denali Xl]

My thought was they use power from one system to feed another.
Have you cleaned the power and grounds. They are a problem on all these trucks. I wish I could help you more but haven't had to do much work on your year truck.
If it has remote start I would go over all the conections. Guys who install them are hacks 90% of the time. Could be a loose wire or bad control box. Now I am grabbing at straws.

Yeah possibky, if power doesn't turn on

Have tried jumping power across the starter? Just see if it's a starter or ignition switch ?

Have tried jumping power across the starter? Just see if it's a starter or ignition switch ?

Not yet, after all the other things I did to it Friday it was dark and temps had dropped and after working all day I was zapped. Bout to go back up there and put old alternator on it so I can get my $165 back. Then will see if I can get to starter to check. There is alot of oil from a leak I see there so it could have shorted something out seeing how everything not working is what can be controlled with the keyfob. Remote start, power locks, and rear lift hatch. Gotta be something dealing with that.

 

[#1taho]

Good place to start for sure. Post back what you found when you get back. I am interested to see what you find.
Weather should be a bit better today with less wind. Still cooler than one would like for out door car repairs

 

[07 Denali Xl]

So I went back. Pressed remote locks still nothing. Manually opened door and left it open. I put key in turned heard one light click. Turned back turned again one light click, on third time heard door chime and think interior light came on. Pressed door locks and they worked. So I then turned key once more, cranked right up. I drove it home and shut it off. I put original Alternator back on. Now keep in mind the first time I put new alternator I disconnected positive cable from battery while working. When I got it home I disconnected the positive again to put the old one back on. Once all was done I reconnected all plugs to alt and battery. Then got in to crank. This time no click, no locks, no lights back to square one. The alternator is not the issue, plus the battery was charged by the new alt on that drive home. Another key note not sure if I mentioned is all the items that don't work ate the things that the key fob controls. The locks. The starting, the interior lights, The rear lift gate. Discussing with my dad it's seems like its acting as if it's in a theft mode. No locks, cranking, etc. But when key turns lights on dash along with theft come on and go off as normal. Another key point. The gear positions PRND1D2 are lit up, but the dash that is usually under the gear your in is not showing. So if I go to neutral or whatever it never underlines that gear.

 

[#1taho]

Yes. Definitely puzzling. Something like this had to diagnose over the Internet. But at least it started and it's home.
I know you had the battery on charge but I would get it load tested. With the weather going hot and cold like it is this is the time of year they go. It may have 12 volts but not be able to hold any amps. Do you know how old the battery is ?

 

[07 Denali Xl]

Yes. Definitely puzzling. Something like this had to diagnose over the Internet. But at least it started and it's home.
I know you had the battery on charge but I would get it load tested. With the weather going hot and cold like it is this is the time of year they go. It may have 12 volts but not be able to hold any amps. Do you know how old the battery is ?

Three years old. I'm putting it on a charger. We will see what's next.

 

[07 Denali Xl]

So been gone all day with battery charging. Almost full when I got home. Hooked all battery cables back got in nothing. On the display some things it's been showing are service suspension system, that changes to park assist off, and some times stabiltrak off, TRACTION CONTROL OFF as well. Now when messing with radio FM plays but when I went to X it now says "XM THEFTLOCK" SO IM STILL thinking its in a theft lockup mode somehow. How I unlocked it today to get it to run I don't get. Also the headlights come on but I can't make them high been. Emegercncy flasher don't work either but when it started working today that is what came on so I knew it was working then.

 

[#1taho]

I think you can do a relearn on that. But not sure how to do it. I will try to find something on this if I can.

 

[07 Denali Xl]

Been researching still. I've ran in to a few post about a ground wire on the passenger side cylinder head. I can't get back there or under it to see this wire is my issue. Gonna dig into it today.

I have the shift indicator issue as this guy did

"The key to me figure out my issue was that the position of the shift lever changed the behaviour of my problem. I don't remember how I figured that out, but it turned out to be very important info. I started tracing the wiring diagrams in my repair manual. I focused on the shift position switch that's mounted on the side of the transmission. I individually checked each wire against the repair manual for ground, power, etc. I found that the ground wire to the switch did not have ground. Traced that to a broken ground connection on the rear of the passenger side cylinder head. Apparently the ecm, bcm, or something along those lines used this same grounding point and due to the lack of ground they were backfeeding through other circuits. Fixed that ground point and everything was fine!

So, I never really did find out about the BCM programming issue since I didn't have to replace mine. I think it's rediculous that I'd be at the mercy of GM to program a part - that makes it impossible for me to work on and repair my own vehicle - I think that's illegal or something!
"

 

[#1taho]

At least you found it and cost you 10 cents for a conector and a few days of down time.
Great job.
Now if you were at the dealer that's a $1000 repair!!! Saved your self a bundle

 

[07 Denali Xl]

At least you found it and cost you 10 cents for a conector and a few days of down time.
Great job.
Now if you were at the dealer that's a $1000 repair!!! Saved your self a bundle

Actually I havnt fixed it. That was a quoted post. I have not been able to locate this ground the guy is talking about. I'm under it right now Ive ran jumper cables from ground to different parts of body. I'm assuming the things not getting power are not getting a ground at the body. I'm tracing wires under car. But I can't see anything on passenger cyclnder head. There is a grounding strap from the body, beside master cylinder, to rear of drivers side cylinder head. Everything looks good on that ground. I was also able to touch wire across starter. It's working other than the key is not telling it to fire. Waiting for a friend to bring a code reader. There is an engine light on the dash. But again that gear shift indicator not getting power seems to be same as the guy I quoted. I just got trace it to the issue. A lift wud be nice. ..

 

[Nguyt518]

On my 2009 denali, IIRC, interior lights very dim, remote lift gate didnt work, and the truck would sometimes die. Ground wire issue. Problem solved.


On my folks 2009 escalade, IIRC, some parts of the dash was lit up, parts of the climate control worked, some interior lights worked. Towed it to nearest Cadillac dealer, diagnosed it as a ECU issue. Replaced ECU. Problem solved (if you can diagnose ECU issue, its relatively inexpensive/easy to replace...dealer got us for like $1500)

 

[07 Denali Xl]

On my 2009 denali, IIRC, interior lights very dim, remote lift gate didnt work, and the truck would sometimes die. Ground wire issue. Problem solved.


On my folks 2009 escalade, IIRC, some parts of the dash was lit up, parts of the climate control worked, some interior lights worked. Towed it to nearest Cadillac dealer, diagnosed it as a ECU issue. Replaced ECU. Problem solved (if you can diagnose ECU issue, its relatively inexpensive/easy to replace...dealer got us for like $1500)

Which ground wire on yours?

 

[07 Denali Xl]

Which ground wire on yours?

I've added a YouTube video of my issue here

 

[Nguyt518]

Which ground wire on yours?

I don't remember, the shop fixed it.