2010 GMC Sierra Hybrid.
Sat for 6 days then was completely dead. thought it was the 12V battery so put it on a charger/booster and still no dash lights or anything.
anyone have any idea of what to look for?

Back Story:
Purchased from an Auction and know the history but don't know the history if that makes sense. I know all the maintenance but haven't spoken to anyone who knows the vehicle.
Timeline:
Friday I check out the vehicle in person and start it. All seems good. Shifted gears but couldn't drive it. I was happy.
Saturday auction happens, it is driven through the auction house and my bid wins.
Monday I have a tow truck pick up the vehicle to take it to my mechanic and I drove it onto the lot and parked it. Mechanic says he will get to it the middle of the following week. no rush all still good.
Sunday I go have a look at the truck to put some tires in it for the mechanic. It is completely dead, fob doesn't work, vehicle doesn't start and no dash lights or anything. Completely dead.
I think okey, maybe I left something on. I called the mechanic on Monday to give him a heads up and tell him about the tires and the dead battery. He said no problem, he will figure it out.
Today I get a call that he cant start the truck and even with a big charger/booster on it it is still completely dead with the interior and dash lights not coming on.

That's my story. any help would be great. Has anyone seen anything like this before?
I suggested fuses and the battery cables.
I was counting on the vehicle as my daily driver next week.

Thanks.

 

You've come to the right place.
There many people on here with more skill than me but this is my suggestion.

Take out your 12 V battery, charge it and bench test it.

While it's out, remove your service plug under the rear passenger seat.

Replace service plug, install fully charged 12 V battery.

You should be good to go now.

I have had the same issue and welhen the tow truck showed up about an hour after installing the new 12 volt battery and having the no-start event, I turned on the ignition to shift the truck to neutral to tow it onto the flatbed. I decided why not try it one more time and she fired right up. Never had a problem since installing a AGM 12 V battery.

These trucks draw a lot of power from the 12-volt battery even when off, hence the quick connects on the 12 volt batter y to allow for easy disconnect if you're going to leave the truck sit for longer than a week or so.

FYI the 12 volt battery does not start the truck. It merely activates the electronics to allow the high volt battery to crank the engine through the drive motor.

You may need to clear DTC codes first.

If the high voltage battery for some odd reason has become discharged, which seems unlikely because it drove less than a week ago.

There is a protocol to charge the high voltage battery with a 30 amp charger connected to the 12 volt battery.

Do check fuses 8,9 and 10 in your Hybrid (small) engine compartment fusebox.

Do you have the owners manual with the hybrid supplement?

 

Today I opened the door of the truck after unlocking it with the key.
it started honking so I put the key in and turned it. The truck started.
No one did anything to fix it.
Do I trust it?

 

Check the (-) ground cable from the battery to the chassis.

I have had batteries fail in open circuit, i.e., 0V between terminals, but temperature and vibration (or none at all) can complete the circuit, So still could be a bad battery. Out-of-vehicle bench testing is warranted as that will show high resistance in the scenario I describe.

Concerning the safety plug:

There is ONE reason to remove the safety plug. ONE. ONLY ONE. It is to disarm the HV battery for safety when working on the HV system.

Removing and reinstalling the safety plug has ZERO diagnostic or corrective effect. In fact, it is often detrimental to do so because people unfamiliar with it's operation improperly install it GUARANTEEING a no-start condition.

 

Thank you Sir.
The issue was gone for the weekend until I went to leave for work Monday morning.
Turns out it was a battery cable.
The main cables were tight at the battery but a secondary cable with a 10mm nut was loose. Once tightened everything seems normal. Time will tell.

My next adventure it to figure out what life is left in this 15 year old Hybrid battery and what to do about it.

I saw a testing procedure in an older thread using Torque Pro
I may go that route.
I’ll use the search function to see if there are any ways to get a rough idea from just driving the vehicle to see how it acts.

 

Yep. That was my thread:

https://electricvehicleforums.com/fo...results-31736/

Basically, through the entire battery operating range of the test, the 20 block voltages should not deviate by more than 0.20V. 0.30V is marginal, but in most cases, it's either pretty tight or a mile wide. GM did not handle thermal management well at all on these batteries, and they use them VERY aggressively - way beyond their rating. I've witnessed a Sierra pull 210A out of the battery on a hard launch. They're only rated for about 130A.

In all likelihood, the battery is in bad shape, but I'd love to be surprised.

 

Yes, that’s the thread!
I was hoping you were still helping people with this.

I’ll take a look at it on the weekend.
I hope it works with iPhones.

I saw that you were recommending replacing cells using Prius batteries from the upper 1/3 states so they haven’t had the heat abuse. I’m in Canada (Toronto area) so that’s good.
vehicle has about 110000miles on it. 175000km.

 

It does not work with iphone. There are "torque" apps for iphone, but they are NOT by the same developer. You'll need an android tablet or phone.

Canada + 110K miles actually might be okay. If you drive like a hoodlum, probably not. Hard driving, miles and especially heat are the killers.

x

 

I’ll figure it out.
I have lots of old devices.
I’ve had the vehicle in my driveway for 4 days. Don’t know the way it was used in the past. Could go either way it was owned it’s entire life by the province of Ontario Ministry of the Environment

thanks again

 

My gut says it's got a good chance of being in decent shape.