2007 Yukon Electrical Problems

[shanetx]

Apologies if this is a duplicate, but I searched around and couldn't find another thread with exactly this problem.

Here are the current symptoms:

The engine does not start or even turn over. After turning the ignition switch to on, the following messages flash on the green LCD info screen:
STABILITRAK OFF
STABILITY CONTROL OFF
PARK ASSIST OFF

The Check Engine, Traction Control and ABS lights stay on.

The following do work:
A/C (not the compressor, just the fan and controls)
Radio/ NAV system
Headlights
Heated seats (although the indicator lights don't work)
Windshield wipers (although they only work when turning the switch to the highest position)
Front power windows

The following do NOT work:
Door locks
Dome lights
Remote key fob (I hear a faint click when I try to lock/unlock, but nothing happens)
Rear power windows

This is not an exhaustive list; just what I've noticed.

I hear the fan from the ambient temperature sensor above the driver's head running, whether the A/C is on or not. I'm not sure if this is new, or if it's just the first time I've heard it due to me sitting in the car in complete silence.

When I turn the ignition to the start position, absolutely nothing happens. Motor doesn't turn over.

Here's how I got here: Leaving the office, after turning the ignition switch to start, I heard a pop about half a second before the starter engaged. On my 25-minute drive home, noticed the headlights would slightly dim occasionally for a few seconds.

At home, when I turned the ignition off, everything electrical died immediately, and nothing happened if I turned the key back to on. Power doors wouldn't unlock, etc. As if the battery was unplugged or completely dead.

I connected a battery charger to "jump" mode (50 amps) and turned the ignition on, and it started acting like I've described above. I charged the battery for 6 hours overnight (10 amps) and nothing changed. I pulled the battery and took it to an auto parts store, they said the battery is charged and normal. I also tried jumping the vehicle using another car and cables.

I cleaned and scraped (wire brush and sandpaper) the battery and cable terminals at the battery, as well as the connection of the ground cable to the engine block.

I used a test light to determine there is power on the other side of the 175A mega fuse, so I assume it's not that. I tightened the nuts on this fuse.

I'm hoping to avoid having it towed to a dealership.

Any ideas would be very appreciated! Thanks.

 

[joshcarl]

you could try replacing the starter relay first, but it sounds like you might have to take it to get looked at. do you have a code reader to do a quick scan?

pic of the starting circuit:

 

[shanetx]

Thanks for the reply joshcarl. It seemingly randomly started working last night. As a last resort I started the passlock reset procedure and had left the ignition in "on" position for about 20 minutes. After pulling the key for 30 sec and reinserting, it started. So I drove it to the dealership this morning before it happens again and I have to tow it.

I'll post the results when I hear back.

 

[fiatdale]

Mine had some ghost electrical issues like this too. I traced it back to the air ride compressor. Unplugged it and never looked back. Havent had that issue again.

 

[dragthepaint]

Any further info.......I'm dealing with exact issue now, mine was caused by a completely drained battery tho.

 

[osidesurfer365]

I had this exact issue. It was the negative battery cable. I had my mechanic replace it and it works perfectly now. Here is the link to the thread I started.

http://www.tahoeyukonforum.com/forum/showthread.php?t=62488

 

[shanetx]

Followup

After taking it to the dealership back in January, they were unable to replicate the problem. They did note that both battery cables were showing high resistance, and the ECM had lost contact with the BCM (body control module).

I replaced the negative battery cable and that seemed to work for several months.

The problem started again, this time even worse and more frequently. One day while driving, if I took my foot off the throttle my NAV system would reboot and the battery voltage meter would drop to almost nothing, then would recover. Stuck in a traffic jam, I had to keep slight pressure on the throttle to keep the RPM's up and avoid this. As soon as I turned the ignition off, everything died; same symptoms as my original post.

I replaced the positive cable last weekend, and no problems since. Hoping that was it.

So it appears the half-functioning electronics situation is related to the BCM losing contact, which could probably be caused by various things in the battery/charging system, including battery cables having issues, loose contacts, a fully drained battery, etc.

Sidenote: if you're replacing the positive cable, don't overtighten the nut on the starter solenoid. I messed mine up and had to replace the starter assembly. I believe it was the original and I'm at 151K miles.