Hello everybody, new to the forum and hoping someone can help.

2016 Tahoe, 90k miles, bought in Phoenix AZ 2 on 9/6. Truck is originally from Houston Texas. Drove it up to Flagstaff, AZ where we live.

Drove it for a few days, no issues.

On 9/10 I took it to our mechanic who did oil, trans flush, coolant flush, plugs.

Next morning, 7am 9/11, truck won't start. Lights ok, radio ok, no crank. Nothing, dead as a door nail. I moved battery terminals, negative was loose. Tighted it and truck started.

Next morning, 7am 9/12, no issues.

Next few mornings truck started fine.

Temps in the area are starting to drop from low 60's overnight to low 50's overnight.

Morning of 9/15, outside temp high 40's, 7am truck won't start. Mid morning, 60's outside, teuck starts fine.

Morning of 9/16, outside temp of 45° 7am 9/1, truck wont start. Move termials, nothing. Still tight. Around 10am truck starts no issues. It's 66°

Note: temp on 9/16 has now dropped to 40's overnight here.

Called mechanic, suggests I clean all terminals, so I do as well as get a new battery, Duralast Gold H7 DLG 94R.

Incidentally, the new battery is 800CCA old one was 770CCA. FYI, also, the truck has 2 batteries fwiw.

Next morning, outside temp at 44° 6am 9/17, truck starts fine.

Today, 9/18 outside temp 42° 6:30am truck won't start. 10:30am truck starts fine. 63°

I'm baffled!

Does anyone have any suggestions???

After mid morning when temps seem to go into 60's 70's the truck never has a problem starting. Strong, no lag, nothing.

Amp guage reads 14+

Thanks for your help!

 

Does it try to turn over at all, or make a click?

I am wondering if your issue could be a sticky starter solenoid or one of the relays under the hood. Next time it happens, slip under there and beat on the starter a couple times, or tap on the relays under the hood that seem ignition related, then try again. This happened to me recently - intermittent starting with my 1996 C1500 - and I had to replace the starter.

 

JF, it doesn't do anything. Not a single click. Dead. Then as the day goes on and temps rise, usually after 10am, it starts just fine and never has a problem at all until the next, chilly, morning. Except the chilly morning right after I put a brand new battery in, Tuesday. Today Wednesday, back to nothing, until, 10:30, then perfect start up.

I will try banging on Solenoid tomorrow morning as well as any relay related to starting.

Thanks

 

Another diagnostic tool in this case that might be useful would be a hairdryer. I would avoid a heat gun as they get took hot. Hit the relays under the hood with heat for a couple minutes, try cranking again. Hit the starter itself with some hot air for a minute or two, try again. I guess there is no ignition switch on a 2016 vehicle - i.e. its pushbutton. But, warm that switch up too, or the ignition switch if it does use a key to start.

 

JF, good suggestions. I'll try that tomorrow morning.

The really frustrating thing here is that it needs to be cold, in the 40's for me to replicate the symptom.

RF

 

You have a "failure to crank the engine" issue, different from a "engine cranks and doesn't start" issue. This should be straightforward for the mechanic to troubleshoot if you leave the vehicle overnight with him.

Some mechanics would swap the starter relay with an identical one from the fuse box under the hood, and see if the situation is better or same. Others would jump the starter solenoid small terminal from battery positive terminal and see if that gets the starter to spin the engine.

 

Thank you everyone for your feedback and suggestions.

At this point I don't think temperature is a factor. There have been multiple days where the Tahoe wont start even as the Temps get into the 60-70° range. Instead the Tahoe will always start sometime later in the morning without issue usually after 11am.

I dropped it off at my mechanic so he could have it for a NCNS event in the early am. He began troubleshooting at 6:30 am and it wouldn't crank nor start.

He pulled the battery and tested it. Came back good. Fully charged it and put it back in.

Signal gets to the fusebox and isolator which has both batteries connected to it on the firewall next to brake booster.

He said the power dies somewhere before getting to the starter which he tested and claims is fine. He powered the starter directly and the Tahoe starts right up strong.

He cleared over 30 codes for various issues. Mostly electrical. He didn't elaborate so I don't have much info.

I took the Tahoe home at 1pm on Friday. He said it started around 9am that day but assures me time has nothing to do with whats going on. My experience is that after 11am or so it starts just fine all day until the next morning after sitting all night.

I'm taking it back to him on Monday, tomorrow, so he can keep evaluating and testing.

He mentioned the BCM but I'm confused as it won't start in the morning until after 11am sometime and then run all day and night without issue.

Has anyone had an experience similar that can shed some light on the next steps?