Tahoe Starting Problem

2003 Chev Tahoe, drove this morning with no problems. This evening I went to pull it into the drive way and it wouldnt start (or crank). Thought the battery was dead went to jump it and still no start. Tried it again after it sat about two mins and it cranked and startd normally as if there was no problem but then mysteriously shut off on its own after about 3-4 seconds. Wouldn’t start or crank again…waited a little and it repeated the same thing then nothing. All the dash lights and head lights come on normally.

Forgot to mention that its a 5.3 liter, 2 wheel drive, nothing fancy.

Next day:
Turned the key, engine cranked fine and ran for a few seconds then died again. Repeated the same thing and it stared. I suspect something like a relay may be failing or a computer sensor having problems. Seems to be running fine for now.

Sounds like an intermittent sensor. You can go to a parts store to get a scan of stored codes. Post them here. There are just a few that will kill the engine without setting a hard code(ie the dash check engine light).

I will have the computer checked for codes today because the problem occured again this morning. I wasn’t thinking about codes because there were no trouble lights and the check engine light never came on. Never the less, I will have the computer scanned. I agree that it seems like a sensor, just as if you unplugged the MAP or intake sensor making the engine shut down. I would like to get a schematic and/or a system description to see what is controlling the starting and running systems.

I think that you need to check all of your power connections re: the battery - clean the terminals, check the wires for corrosion, check the grounds (especially).

Your battery may be at the end of its life. If it is 5 years old, or more, replace it.
Your battery probably has battery cables attached to the side with 8 mm (5/16") screws. If so, you can improve the electrical connection, if it’s poor, by loosening each screw a couple of turns, turn the cable ends sideways (left and right) a few times, and re-tighten the screws.

I have the problem solved (so far). I was checking it out tonight and started with the battery connections, all were perfect and the battery is not very old. I called my son out to manipulate the ignition because I was still thinking there was a relay problem. With him holding it in the start position I gently tapped on the relays and as I did he said that the check engine light was flickering in a certain area. I thought there was a loose connection under the panel and took it off. We tried it again and nothing happened. I layed the panel back down and he tried it again and it started. I looked closer and saw a partially burnt 20A fuse. Im going to try to link to some pictures, hopefully it works. You will see that the PCM B fuse is burnt on one side but has just enough connectivity to work some of the time. I replaced the fuse and it starts and runs great, Ill drive it for a day and see if it lasts.
The fuse picture is a little blurry but you can see the problem.

Good detective work.

Tahoe started and ran great this morning, I think this was the problem. Thanks to those who replied and hellokit and gigroller for keeping me in the area of the malfunction.