Simply, no clue.

[mrbigles]

Here's the fun I've been having with my 99 Yukon SLE.

Last friday, I drove from work, to the golf course, played, got back in the truck, and, it was in limp mode. The tach, speedometer, and gear display didn't work. Had it hauled to the mechanic and it was diagnosed with a bad ignition switch. It was replace on Monday. I picked up the vehicle and drove it Monday night and Wednesday morning. Wednesday afternoon, it wouldn't start. No codes, no nothing. It turns over for about a split second and then dies.

On Thursday, a buddy of mine brought over a $3000 code reader and scanned the whole thing. No issues. He then tried to start it for giggles. The SOB started!!! Started throughout the day and got me home from work.

Went out last night to go up the street to the grocery and, you guessed it, it wouldn't start. Having the same problem today.

I'm at my wits end here. Any guesses, tests, or hail mary's any of you have will be greatly appreciated!

Have a great weekend!

 

[HiHoeSilver]

Here's the fun I've been having with my 99 Yukon SLE.

Last friday, I drove from work, to the golf course, played, got back in the truck, and, it was in limp mode. The tach, speedometer, and gear display didn't work. Had it hauled to the mechanic and it was diagnosed with a bad ignition switch. It was replace on Monday. I picked up the vehicle and drove it Monday night and Wednesday morning. Wednesday afternoon, it wouldn't start. No codes, no nothing. It turns over for about a split second and then dies.

On Thursday, a buddy of mine brought over a $3000 code reader and scanned the whole thing. No issues. He then tried to start it for giggles. The SOB started!!! Started throughout the day and got me home from work.

Went out last night to go up the street to the grocery and, you guessed it, it wouldn't start. Having the same problem today.

I'm at my wits end here. Any guesses, tests, or hail mary's any of you have will be greatly appreciated!

Have a great weekend!

Start with battery cables and connections.

 

[exp500]

On the work truck I use 3/8 bolts to the battery with 2 nuts and use washers 1 or 2 under and between terminals, take the rubber off, tighten bolt to batt then use nut to tighten terminals. Plus is jumper cables fit easy.

 

[mrbigles]

Battery and cables attached are in good shape. Thanks

 

[willxfs]

My rig, 1998 2 door, used to to something similar. For a while it would run just fine. Then every couple of months it would start for a split second and then die. I could sometimes get it going by moving the steering wheel up and down with the tile lever. I finally put a new ignition switch in it and its been trouble free since. I see you have changed the ignition switch with no luck. Years ago, my rig wouldn't start periodically with very similar symptoms of what I previously described. That time it ended up being the wiring harness connector on the fuel pump. When it wouldn't start, I could sometimes get it going by reaching up around the top of the tank and wiggling the wiring harness. It progressively got worse and worse (happened more and more frequently). I ended up dropping the tank and just changing out that connector. Then a few years later when the fuel pump started making lots of noise, I changed out the whole pump assembly including a new connector for the wiring harness. No more problems starting since. Good luck and keep us posted.

 

[petethepug]

BCU? Prolly a cold solder joint on one of the boards. If it’s temperature related, it will help support the theory. The bad ignition switch may have fried it.

My buddy had an impeccable Bimmer 525 that would intermittently stop cold in it’s tracks. He mentioned it to a coworker that he was ready to light it on fire. That dude was a crack airline mechanic. He pulled the ecu and found a cold solder joint that broke continuity when placed in the fridge for 20 min. A heat gun reversed the break to confirm the theory and they re-soldered the discolored area to cure it.

It’s an odd occurrence that can lemon law a new car. We have an Audi allroad with the 2.7 V6 twin turbo motor. It developed an misfire that the ecu posted a check engine light on. It was a CPO car the dealer pumped 60 hours diagnostic time into.

It got a new ECU, plugs, wires, fuel checked at a lab, new tank of fuel, compression test, injectors cleaned and new knock sensors. The factory finally allowed the tech to follow up on a hunch he had. The head on the bank with the detonation was replaced. Viola! There was a flaw in the casting of the p/s head. It was the 2nd known occurrence the tech was aware of on the 2.7t motor motor, but Audi never issue a tsb.

The weird, uncommon stuff will drive ya [emoji1645] nuts!


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[petethepug]

BCU? Prolly a cold solder joint on one of the boards. If it’s temperature related, it will help support the theory. The bad ignition switch may have fried it.

My buddy had an impeccable Bimmer 525 that would intermittently stop cold in it’s tracks. He mentioned it to a coworker that he was ready to light it on fire. That dude was a crack airline mechanic. He pulled the ecu and found a cold solder joint that broke continuity when placed in the fridge for 20 min. A heat gun reversed the break to confirm the theory and they re-soldered the discolored area to cure it.

It’s an odd occurrence that can lemon law a new car. We have an Audi allroad with the 2.7 V6 twin turbo motor. It developed an misfire that the ecu posted as a check engine light on. It was a CPO car the dealer pumped 60 hours diagnostic time into.

It got a new ECU, plugs, wires, fuel checked at a lab, new tank of fuel, compression test, injectors cleaned and new knock sensors. The factory finally allowed the tech to follow up on a hunch he had. The head on the bank with the detonation was replaced. Viola! There was a flaw in the casting of the p/s head. It was the 2nd known occurrence the tech was aware of on the 2.7t motor motor, but Audi never issue a tsb.

The weird, uncommon stuff will drive ya [emoji1645] nuts!


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Sent from my iPhone using Tapatalk

 

[petethepug]

Huh? iPhone double posting, sorry


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[alpinecrick]

Yes, start with battery cables, then do this:

On the work truck I use 3/8 bolts to the battery with 2 nuts and use washers 1 or 2 under and between terminals, take the rubber off, tighten bolt to batt then use nut to tighten terminals. Plus is jumper cables fit easy.

 

[mrbigles]

Thanks for the input everyone. I've dropped it off at the mechanic but have tested that, when the truck is hot (day temp), it won't start. If it's cool outside, it fires right up. Fingers crossed he'll find the problem.