No ground to coils.

[Khaan86]

Hello, I have a 2006 Envoy Denali that has been giving me problems lately. It stalled while driving two and a half weeks ago, leaving my friend and I stranded in the middle of the street. The truck would crank and crank but it wouldn't start. I decided to get out and grab my tools so that I could disconnect the battery and hopefully clear any sensors that were causing me problems. Well, I couldn't have picked a more terrible time to open my liftgate and lean for my tools... A drunk driver plowed into the back of my truck at 40 mph. Luckily, my buddy saw him coming and yelled at me about 3 seconds before impact. I looked over my shoulder and jumped as he struck my leg then the rear of my truck. I landed on his hood with a sore leg, but greatful to be alive! Anyways, the next day at the tow company's yard, the truck fired right up. It was fine for a week and then started acting up. It stalled at a friend's house and wouldn't start for two days. Finally, it started and ran fine for a couple of days. Then, it started mising occasionally while driving. The RPMs would completely drop down to zero and if I pumped the pedal, sometimes they would kick back up to over 1,000 and the truck would stay running. This all mainly happened while I was going about 55mph. Other times, it would just stall completely and I would be forced to shift it into neutral and start it back up. For some reason, when I was moving, it seemed like I could get it to start again. Then it ran fine for a few more days, no problems at all. It wouldn't start again at the end of last week for a whole day. I got it to start and it ran for one day. I was driving home and going about 25 mph and it suddenly stalled. No warning or anything. I coasted to a stop and tried to start it but nothing. I had to get it towed home. It's been sitting in my driveway ever since. I've been trying everything I can think of. I put a fuel pressure gauge on the fuel rail and verified that the gauge jumps to 60psi when the key is turned and then settles to about 58psi. I've checked for any codes and the only ones I was able to pull were while it was running like crap and it stalled so I threw the code reader on it before starting it back up while driving. I ended up getting two codes: P1133-Heated oxygen sensor insufficient switching bank 1 sensor 1, and P1153-Heated oxygen sensor insufficient switching bank 2 sensor 1. I have not gotten these again, and was wondering if I got these because of it running rough and stalling or if they are a symptom of the problem. I checked the throttle body to make sure the butterfly wasn't getting stuck as some members have reported and all was well. I took it off and cleaned it while I was at it. Then, I decided that since I had checked fuel and air, I would check spark. I pulled a plug and cranked the motor and didn't get any spark. i put the plug back in and decided to replace the crankshaft sensor since i had read that it would cause the motor to crank and crank, but wouldn't give me any spark. Nothing changed. I had replaced the ignition switch since i also read about those doing crazy things and just wanted to rule out the cheaper and easier culprits. I grabbed my test light and checked for voltage to the coils. I'm getting voltage to the coils as well as the reference from the PCM. However, I'm not getting any ground. I read a wiring diagram that says the coils are grounded to G109 on the left side of the motor. I could not locate any such ground and I looked very thoroughly. My diagrams and pictures show the ground being in the same sheath as the knock sensor and then continuing above the sensor where it should be bolted into the engine. There is no bolt, no wire, and no indication of a ground having been there. Any chance the diagram i have is wrong? I have followed the ground cables from the coils to the underhood fuse box and I don't know where they go from there. I really want to get this thing started! Any suggestions? I'm wondering if the PCM has something to do with it or if that is unlikely since I'm getting voltage and reference ground at the coils from the PCM?

Thanks in advance!

Kyle

 

[c good]

I had similar problems but mine would blow the fuse for the coil packs, fuel injectors and something else I don't remember. I would replace the fuse, it would run for a few days and then act up again...blow another of the same fuse and turn over but not start. Turns out it was a shorted out coil pack. It would short out when it got hot and blow the fuse. You may have one on the edge of complete short. I ended up replacing all the coil packs and never had any trouble since. HTH c good

 

[Khaan86]

I forgot to mention that I had already disassembled the fuse box to check for any blown fuses. I also checked the inside of the fuse box to see if there was any corrosion or broken wires and didn't see any. I'll check the fuses again to be sure. This one has me stumped. Like I said, I was wondering if the PCM could be acting up, but I would think that there would be more symptoms. Never had a PCM problem though, so I"m not entirely sure of what the symptoms would be. Any other ideas?

 

[IllogicTC]

Strange that the grounds are running to the fuse block, you're right that the diagrams don't mention this.

I'm looking at G109, it's toward the back on the left (right when looking in from the front) of the engine. Looks to be by the third cylinder back a few inches from where the block meets the oil pan, and it also appears according to the picture to be at least partially obscured by something.

Or are we talking the I6 engine here? I was under the assumption that with the Denali you'd have the V8. The I6 has them running through the fuse block first. They then still wind up on "lower left of engine."

 

[jimmyjam]

G107 & G108 are on the driver side engine block

G109 is on the passenger side cylinder head, on the front on the right (toward the intake manifold), behind the water pump inlet.

 

[Khaan86]

Strange that the grounds are running to the fuse block, you're right that the diagrams don't mention this.

I'm looking at G109, it's toward the back on the left (right when looking in from the front) of the engine. Looks to be by the third cylinder back a few inches from where the block meets the oil pan, and it also appears according to the picture to be at least partially obscured by something.

Or are we talking the I6 engine here? I was under the assumption that with the Denali you'd have the V8. The I6 has them running through the fuse block first. They then still wind up on "lower left of engine."

I thought it was strange too that they ran to the fuse box.

I was hoping to follow the wires down to G109, thats why I followed them in the first place. No such luck. As I had mentioned, when searching for G109 on the lower left, I found nothing. I see where it could bolt to, and I believe it to be the spot that the diagram is referring to. It looks like the ground is supposed to be in the same sheath as the knock sensor wiring and then continue past the knock sensor according to the diagram. Wouldn't you agree? However, I have peeled back the sheath from the knock sensor wiring and do not see any extra wire, especially a ground.

Its the V8 motor.

 

[Khaan86]

G107 & G108 are on the driver side engine block

G109 is on the passenger side cylinder head, on the front on the right (toward the intake manifold), behind the water pump inlet.

G109 for the V8 is on the passenger side cylinder head? Or do you mean for the I6?

 

[jimmyjam]

Yes v8.

There's only one cylinder head on an i6

 

[Khaan86]

Yes v8.

There's only one cylinder head on an i6

Touche, lol. I'll have to remember not to reply to posts when just waking up. Didn't even think before asking!

So how do you know G109 is on the passenger side? Every reference I have found shows it to be on the driver's side lower left. Also, any should I expect the grounds to go straight to G109? Or is it likely that they enter the fuse box, and then leave and go to G109.

 

[jimmyjam]

So how do you know G109 is on the passenger side? Every reference I have found shows it to be on the driver's side lower left. Also, any should I expect the grounds to go straight to G109? Or is it likely that they enter the fuse box, and then leave and go to G109.

IDK what you and illogictc are smoking but please pass that lol

heres 107 & 108 for shits and giggles

 

[Khaan86]

I have a subscription to mitchell online, and it shows G109 as being the ground that your diagram calls G107. I don't see that ground, whether its called G107 or G109. Where did you get your diagrams from?

 

[jimmyjam]

i got them from alldatadiy sub for my 2006 tbss. I also have the paper service manuals for 2006 and, while i find it impossible to find any info in them, I was able to find the pic of g107 and 108 that i posted prior in the 5.3 engine controls

 

[chicagotransam]

This sounds EXACTLY like what happened to my 05 about 6 months ago. Turned out to be the fuse panel under the hood itself. Had to swap the entire unit and has been running fine since.

 

[Khaan86]

This sounds EXACTLY like what happened to my 05 about 6 months ago. Turned out to be the fuse panel under the hood itself. Had to swap the entire unit and has been running fine since.

I thought it could be the fuse box, that's why I tore it apart completely to look for any signs of corrosion, broken wires in the traces, or any other failure. I had the thing almost completely apart and didn't see anything that would indicate that it was the problem. I had heard and read about many guys having issues and having to replace the fuse box since it is directly above the front suspension and has taken a ton of abuse over the years. However, that being said, I've also read many different stories of dealer's telling them they needed a new fuse box and the problem continued.

i got them from alldatadiy sub for my 2006 tbss. I also have the paper service manuals for 2006 and, while i find it impossible to find any info in them, I was able to find the pic of g107 and 108 that i posted prior in the 5.3 engine controls

I almost went with an alldata subscription, but decided to go with Mitchell since a lot of people were saying that Mitchell has better wiring diagrams. I'm starting to regret my decision since this is the first thing I've needed it for and it pointed me in the wrong direction!

 

[IllogicTC]

I almost went with an alldata subscription, but decided to go with Mitchell since a lot of people were saying that Mitchell has better wiring diagrams. I'm starting to regret my decision since this is the first thing I've needed it for and it pointed me in the wrong direction!

With the actual pictures or in the diagrams? How are the diagrams?

 

[Khaan86]

Okay, so I wanted to keep you guys all updated. I got the truck to start! I followed the coils to the G109 ground as shown in jimmyjam's diagram above. The bolt needed to be tightened down considerably. Jumped in and she fired right up. I let it run for a minute and then shut it off so that I could restart it and see if it fired right up again. Well it didn't! Every time I had been trying to start it, it would crank all day, just not turn over. Now, the starter clicks once when I turn the key, the motor doesn't crank at all. Did my starter decide to give up? Or would you suspect a relay? Seems strange that it started up for the first time in days and then wouldn't even crank... I had hooked jumper cables to it from my other vehicle just to make sure it had enough juice to engage the starter, but that changed nothing.

 

[Khaan86]

With the actual pictures or in the diagrams? How are the diagrams?

Both are misleading. The wiring diagrams state that the coils ground to G109, then in parenthesis it says (located on lower left of engine.) The pictures show G109 as being on the lower left of the engine. However jimmyjam's pictures showed G109 as being on the front of the motor towards the passenger's side. Following the grounds from the coils, I was able to verify that jimmyjam's pictures were correct and the Mitchell ones were wrong.

 

[KNBlazer]

that same ground you moved, inspect it closer, clean it up with a wire brush...

 

[linneje]

If you are getting one click, from my experience, the starter is getting current but it is seized. Multiple clicks would indicate poor elect - like weak battery or such.

It does seem like a coincidence, but the symptom as you describe should have you suspect the starter.

 

[Khaan86]

that same ground you moved, inspect it closer, clean it up with a wire brush...

I plan to remove and completely clean this ground since it had an air gap, which would allow for corrosion to build up, however, I don't believe that the ground is the cause of the new problem. The ground caused intermittent problems since it was making intermittent contact with the motor, but not once would the engine not crank. So for it to now not crank, I believe that it must be starter related...

 

[Khaan86]

If you are getting one click, from my experience, the starter is getting current but it is seized. Multiple clicks would indicate poor elect - like weak battery or such.

It does seem like a coincidence, but the symptom as you describe should have you suspect the starter.

I figure that I'm going to put the battery on a charger just to be sure I'm getting full juice to the starter since it was cranking but not starting for a week. However, I expect to get the same results. I just want to be sure before going through the hassle of pulling the starter. I see from other posts on these forums that it is a 3 hour job to swap the starter! My question is, is there a motor mount or two that I could disconnect in order to raise the motor up a couple of inches and make things easier? I'm still new to this motor and vehicle, so I figured I would ask. Thank you to everyone who has helped me so far!

 

[jimmyjam]

If I can get my starter out with long tube headers, there is no excuse without them. you may have to remove the cross member behind the steering rack for clearance for removal.

try tapping the starter solenoid with a pipe while someone else turns the key first before you do anything. I've had mine get stuck once.

 

[C-ya]

try tapping the starter solenoid with a pipe while someone else turns the key first before you do anything. I've had mine get stuck once.

This is always on my list of tricks to try before I pull one off. If it works, it can confirm (or deny!) theories you may be pursuing.

 

[linneje]

This is always on my list of tricks to try before I pull one off. If it works, it can confirm (or deny!) theories you may be pursuing.

Definitely try that first. I am not sure that it is a three hour job, though. I was stuck away from home when mine seized, and the shop only charged 1.5 hours labour. Of course they have probably done many before. If it is the first time it usually takes double for me.

I read the repair guide, and it does list removing the crossmember.

 

[Khaan86]

Hey, guys. I cleaned the ground as I said I would, and made sure the battery is fully charged. It cranked and started when I put the starter back on and connected the battery. However, it died after running for about 5 seconds. I tried to start it and nothing. No cranking, no click, nothing. I was left scratching my head. When I got home from work this morning I figured screw it, maybe I'm not getting juice from the ignition for some reason. Don't know why but I just figured I'd disconnect the ignition switch and reconnect it. Well, the truck fired up again and then died after 5 seconds. I can keep disconnecting the ignition switch and plugging it back in and the truck will start for 5 seconds before dying every time. My doors also do not work with the key fob now, and the electric switch on the door doesn't do anything either. Is my PCM screwed? I don't see my anti-theft light blinking. I am beyond frustrated with the electronics in this truck at this moment.

 

[Sparky]

If fiddling with the ignition switch makes a difference, then maybe the switch itself is to blame. Not an uncommon failure, and when they go all sorts of wacky problems crop up.

 

[Khaan86]

If fiddling with the ignition switch makes a difference, then maybe the switch itself is to blame. Not an uncommon failure, and when they go all sorts of wacky problems crop up.

I thought the same thing, so I put a brand new ignition switch in and I have the same results. Starts for 5 seconds then dies. I believe something is staying energized or the computer is looking for something 5 seconds into the truck starting and that's what makes it stall. Then when I disconnect the ignition switch, that eliminates electricity flowing through that circuit, so when I reconnect it and turn the key, it starts once, and 5 seconds later it stalls again when the computer or security system looks for something again. If I leave the truck sit for 30 minutes or so, it will start up and run for 5 seconds then die. Doesn't it automatically turn power off to everything after 10 minutes to keep the battery from dying? I think when it does that, it is having the same affect as me disconnecting the ignition switch. Please tell me if this sounds reasonable or not. It seems logical to me, but as I mentioned, I'm completely new to this truck and motor.

 

[KNBlazer]

have you touched the PCM? if you haven't, can't hurt to take connectors off and reseat them...make sure battery is disconnected prior....


Have you checked fuel pressure while this happens?

 

[Texan]

Could this be a fuel pump/relay problem? What changes when the ignition switch goes
from start position to run position? Just a suggestion.

 

[IllogicTC]

Is it like a good start, then it slows or peters out to a stop? Or runs as it should, then a curt and clean shut-off like you turned off the ignition?

And you said the window doesn't want to respond, nor your transmitter? If you turn the headlights on manually, do the door modules in the front light up like they should? I am curious if there is indeed a communications issue causing some security feature to set off. I know when you're starting up the PCM and BCM chat with each other and decide whether or not it was legit or not; a bad communication path or faulty module would obviously interfere.

Since we're doing a cold-engine start here, I'm also curious as to if the SAIS system is somehow affecting the operation. Both pumps share a common ground for one, and secondly maybe the high draw (the air pump is SERIOUSLY high-draw) is showing some fault in the electrical system, maybe a fuse that's partially failed or something.

There should be no difference between START and RUN ignition switch positions, except START also sends a signal to run the starter. There's three key outputs from the switch: Accessories, Run, and Start.

KEY POSITION: Outputs
LOCK: No selections.
ACC: Accessories
RUN: Accessories, Run
START: Run, Start

 

[Khaan86]

Hey guys, I got this whole issue sorted out! The truck has been running great for about a month now. I just wanted to be sure to thoroughly test it before stating that it was all good. For starters, the initial problem was definitely the G109 ground. So I was on the right track with that and would like to thank jimmyjam for pointing me in the right direction as to the location of this ground. The other problems, as far as the no crank condition, running for 5 minutes before dieing when it would start, and the windows not working, all came from a loose positive wire heading the fuse box. When, I was tracing the ground from the coils to find where they were ground to the motor, I had to move the wire out of my way. It appears that I didn't tighten it down all the way, so I'm guessing I wasn't making a good enough connection for my relays and fuses. Stupid mistake and something I overlooked while pulling my hair out from the original problem lol. I decided to go back over everything I had touched and I found out that wire was loose. It pays to be thorough. I would like to thank everyone for their input and their advice! Thanks guys!

Kyle