Electric issue or sensor issue?

[atsierra10]

Hello,
I have a 2010 Sierra All Terrain 4wd with a 5.3L. Over the past few months, especially when cold but also when it is warm outside, I go to crank my truck after it has sat overnight and it bogs down to about 300-400 rpm for a couple seconds, like it doesn't want to start, and then revs up to normal running rpms without the normal high rev start. But if I shut it off right then and crank it again it doesn't do it. I just replaced the battery last month and had the old battery and current alternator tested under a load and everything checked out. So i put the new battery in the starter battery spot and put the older battery in the aux. battery spot and set up a dual battery set up. All my accessories in the cab appear to shut off whenever I cut the truck off. Also, my low battery light comes on within a minute or two minutes of having the battery switched on. So my question is, do I have an electrical issue somewhere or do I have something like an ethanol sensor calibration issue like I've seen talked about a couple different times on the site?
Thanks in advance!

[Doug_Scott]

When you did your dual battery setup, did you just put it in like you were boosting the truck, or did you get a proper dual battery kit?

I do not understand what you mean when you say the engine bogs to 300 to 400 rpm, but then you say like it doesn't want to start. Is the truck running at 300-400rpm or are you guessing at the cranking rpm? When you say "when cold", is that -20C like here or 55F like in Florida? Cold days here will cause any vehicle to crank slower than normal.

You should go through your post and make the issue more clear.

[atsierra10]

 

This video I found is an example of what it is doing but mine seems to take a little longer to come up than the one in the video. I live in NC near the coast and it does it worse the colder it is but it's the most noticeable below 60-65 degrees. Also, I'm not sure if it's hooked up right but the second battery is grounded to the block and the positive is going to the aux stud on the front side of the fuse panel area.

 

 

 

Sent from my iPhone using Tapatalk

[Doug_Scott]

If your truck is doing what the video truck is dong, it has nothing to do with battery, alternator, or starter motor. Could be IAC stepper motor and passage needs to be cleaned, or plugs, or IAT sensor not reporting actual temp.

Take the second battery positive cable off of the stud you it connected to, and see if there is power at the stud using either a voltmeter or a test light. I do not know if that terminal is like it is on my 2010, but, if it is, there won't be power there unless you install a fuse for it. That stud on my truck is intended to used as a power supply for a trailor. If there is no power there, connecting a battery to it will not work. You should be using a battery isolator if you want two batteries.

[MikeNH]

GM trucks have not had an IAC system since at least 2003 when they went to drive by wire if not before that.

[Doug_Scott]

GM trucks have not had an IAC system since at least 2003 when they went to drive by wire if not before that.

 

Don't know how or why I thought it said 2001 in the original post. That takes care of IAC. Still should check IAT and see it is reporting the correct voltage. Not sure if this table is still valid, but it gives you the relationship between temp and resistance.

 

°F °C OHMS

210 100 185

160 70 450

100 38 1,800

70 20 3,400

40 4 7,500

20 -7 13,500

0 -18 25,000

-40 -40 100,700