2008 Yukon Denali electronics going haywire?

[Burgerx]

Here's a video of the truck.

 

https://youtu.be/FH_p9SVT1aM

 

I really have no idea what's going on guys. I replaced the brake switch, cleaned and reseated all positive and negative wiring under the hood. It's absolutely terrible and frustrating.

 

This is my second gm truck. It's been problem free until this happened and I can't drive it because it's also in some sort of second gear limp mode which is like trying to drive a tractor down the road.

 

I've read countless post about similar problems but don't know where to start. I can't read any codes because I can't connect to the ecm, it's like it's not there.

 

So what I've seen so far is: "service stabilitrak' service suspension system' brake light' traction control off' abs light & no indication of where the shifter is ie prndm" so hopefully someone can give me a hand. (Btw I'm new, I've been using this forum for years to fix vehicles and get advice, hopefully I can also be of help in the future).

[BigRic]

As an update to my original post. I ended up replacing the suspension control module this past week (as someone else noted). Was continuing to get this error (especially on really hot days) and a scanner would show a ton of erroneous "bus communication errors" with only one module showing an actual error (Suspension Control). We decided to start there as it's hard to nail these down with even one module, but at least that had an actual code. According to the mechanic, it nearly fell off the truck when replaced as it was so corroded! For the last 3 days I've had no errors (and when not getting the stabilitrak, traction control, ABS alerts and so on, I would almost always get "check suspension"... Hopeful that this was the final fix! Cost was about $790 dealer installed and reprogrammed.

[BigRic]

Can't see the video, but I'm wondering if it's the same as my 07 Avalanche (sounds like it). I get Stabilitrak, then speedo drops while driving, stabilitrack goes on, then check suspension, etc. Eventually, trans goes into limp mode and I had to replace it back in December following similar trend. Mechanic has been unable to find anything wrong. A scanner shows communication errors, basically the bus is dead. Scared to death to drive my otherwise excellent truck. Hoping someone can help!

 

https://goo.gl/photos/R69ncc9AVX76bo94A

 

[Burgerx]

Fixed the problem guys! Haha these trucks are nuts when there is one bad module. Btw I couldn't even check the tail lights via the back, the rear hatch wouldn't open because it also relies on the lan network. So the Suspension Control Module was toast (up near the spare tire area, why the heck is it outside these trucks, idk).

 

Anyway, it caused basically everything else to malfunction. I unplugged it and it runs great. About 600 for the part, so until I want my bags to inflate again, etc, I'll probably wait.

[Jsdirt]

If this started after you installed the brake switch, I would start there - look over everything closely, and make sure everything is hooked up properly, not pinched, something left unplugged, etc. ...

 

One wire could potentially cause all of this. A shorted or semi-shorted 5v reference at ANY sensor will cause a no-communication ... but the fact that the truck is running tells me that's not what you've got there.

 

Check pin 16, and pin 4 of the data-link connector (wide portion of plug at top, #1 will be top left, & #16 will be bottom right). 16 should have battery voltage, and 4 should be ground. Pin 5 is the ground for most sensors. Wouldn't hurt to check them both.

[Burgerx]

If this started after you installed the brake switch, I would start there - look over everything closely, and make sure everything is hooked up properly, not pinched, something left unplugged, etc. ...

 

One wire could potentially cause all of this. A shorted or semi-shorted 5v reference at ANY sensor will cause a no-communication ... but the fact that the truck is running tells me that's not what you've got there.

 

Check pin 16, and pin 4 of the data-link connector (wide portion of plug at top, #1 will be top left, & #16 will be bottom right). 16 should have battery voltage, and 4 should be ground. Pin 5 is the ground for most sensors. Wouldn't hurt to check them both.

Thanks a lot for the blazing fast reply, I'll check those out. It started before the brake switch, I replaced it hoping it would fix it since it worked for some people.

 

Some people said the throttle body can cause this problem, but I'm really hoping that's not the case.

[silveradosid]

ground points.pdfcheck these ground points

ground points.pdf

ground points.pdf

ground points.pdf

[silveradosid]

ground points.pdfcheck these ground points

[BigRic]

An update to my October post - problem not fixed (and now $800 less rich).  StabiliTrak, check suspension, dropping speedo and other problems are back again.  Not often, and once it happens and truck is off for an hour or so, they clear by themselves.  Not sure what to do next...

[BigRic]

They argued that the modules are ECM-serialized once installed and that they have to start with the "most likely" component.  I've opened a ticket with GM corporate, as I agree with you...

[Jsdirt]

Bill would've been half that if you took my advice ...

 

.....

 

Just don't go to the dealer ...

 

... but, glad you got it fixed.

[XSKIER]

Bill would've been half that if you took my advice ...
 
 
... but, glad you got it fixed.

I spent a lot of time and money on the HVAC system of a 2003 Bravada at an independent repair shop. New actuators, new control panel, new control module. Then a trip to a dealer for a $90 diagnosis of a recently replaced actuator. Fed up with nobody loving my 10+ year old car like I do, I had to fix it myself. I bought a $400 tech2 copy from eBay. Then had to spend about three hours figuring out how to navigate through its menus. The answer? Cabin temp sensor reading 140*F at room temperature. $50 part and 10 minutes labor the climate control works like it is supposed to. Now I will be ready when my 2007 Avalanche starts doing old car stuff.

Sent from my SM-G930V using Tapatalk

[Jsdirt]

Your Fuel Pump Control Module is also located right above the spare tire. Without that $280 or so magic box, your vehicle is dead in the water. Fantastic place for a mission critical component! BUT WAIT ... IT GETS BETTER! When the thing takes a shit ... which it will, mark my words, replacing it yourself won't work! It needs to be reprogrammed into the ECM in order to do what it's supposed to do!

 

GM charges $55 for 3-days of access to this programming, or an obscene amount monthly, and a criminally obscene amount annually ... BUT first, you need a J2534 box, starting at about $1000 average ... then a laptop computer to connect it too ($500 minimum for a halfway decent one), plus your internet connection. If anything should happen to ANY of these components, INCLUDING your vehicle's battery, whatever module you just installed and are trying to program has just become as useful to your vehicle as a BRICK. Imagine spending $800 on a new ECM, and the thing is now JUNK because your battery got a little too low during programming!

 

Gotta love how all the 10 or so modules across the vehicle's network are all integrated today. Try and bypass the BCM - not only will your radio and power windows not work, but the vehicle will not run ... ever! On GMs, the Body Control Module is the hub master. EVERYTHING passes through it! It's conveniently located to be the first thing to be submerged in a flooding situation too ...

 

Just bought a new vehicle? Tired of spending money yet? Well you're just gettin' started!

 

 

There is absolutely NO need for this. Manufacturers are doing this on purpose to grab every single dollar they can out of you, AND the professional technicians that have the burden of diagnosing these turds. Why do GM trucks require a FPCM to run the pump? Wasn't a FUSE and a RELAY enough before? What changed? (the answer to that is ethics, among other things ...) The amount of money a tech needs to spend today just to get his foot in the door is downright criminal. Guess who gets all these costs passed onto? Yep - that $60 grand you signed off on at the dealership is just the beginning. And as time marches on, things are only going to get worse for the consumer - you ain't seen nothin' yet!

 

Next time you're wondering why it costs $120 PER HOUR to get your vehicle repaired, well, now you have the answer. The garages really aren't trying to rip you off (well, unless it says GM on the sign ...) - they're just trying to stay afloat!

 

Sorry for the rant ... but it needs to be said!

[SpartanAutoworx]

JSDIRT

 

YouTube that FSCM you will find there is a plug and play solution out there ?

[Burgerx]

ground points.pdfcheck these ground points

Thanks for those diagrams! I checked all the points and the are fine. I really ripped the thing apart yesterday and I'm about ready to give up. I took it to my mechanic just recently and he doesn't even know what's going on and referenced me to an auto electrical specialist, so I'm just going to drop it off and see what he says.

 

One weird thing is my brake lights work, but when I press the brake pedal, my trailer brake controller doesn't light up anymore like it used to. So maybe there's some type of clue there.

 

Either way, I saw this video here -

 

That really made me kind of throw in the towel, so many things could be wrong. I'll post what fixes it once Marv figures it out.

[Jsdirt]

Best thing anyone can do is repair their own vehicles. I've been doing this a long time, but there's 3 things I won't touch - glass, body work/paint, and front end alignments. Any time I pay someone to do those 3 thing for me, something gets frigged up.

 

Was just cleaning the glass on my SIlverado  in the sun - could see all the overspray the body shop got all over my glass, and the attempts to razor-blade it all off. Also can see "fingerprints" all over the paint - someone put a little too much pressure on too thin of a rag while polishing. Looks awful.

 

Had a windshield put in my '93 940 to fix a water leak, and get rid of the sandblasted OE windshield. They stripped my passenger side wiper arm, and mis-adjusted the driver's side one so it was way up on the windshield when parked.

 

Front end alignment in my Grand Marquis - I get home and check the guy's work. Both pinch bolts on the tie-rod  collar were LOOSE! WTF. To top that off, my steering wheel was sideways going straight. Went to another shop for an alignment on our old '89 S10 Blazer - left the shop with another sideways steering wheel.

 

Back before I had a tire machine and balancer, I bought a brand new set of Amercian Racing polished aluminum mags for my '72 El Camino. They stripped a couple studs by cross threading the BRAND NEW lug nuts, then nicked the finish when I made them fix it. Guy comes out of the bay squealing the shit out of my power steering, and he's laughing about it. Took quite a bit of self control to keep from absolutely losing it. Bought a tire machine and balancer the next day!!

 

Those are just the stories I can recall off the top of my head - I've forgotten many more, like when I discovered my upper control arm loose after driving 2,400 miles to Phoenix - alignment guy never tightened the bolt!