I unhooked the negative cable on my battery this afternoon for 30 mins to clear my brake and abs lights (had a brake line blow out last week, just finished fixing it today). Now after I hooked the cable back up, it will crank but not start. I can hear the fuel pump buzz when I turn the key to on. I can keep it running if I give it gas as I'm starting but as soon as I let up on the pedal it dies. This is really frustrating because it just ran fine before unhooking the battery! Did I trip the security? I read through the owner manual but it didn't say much. I also waited an hour or so to see if it could come out of it (older GM's do this) but still no go.

The worst part is it doesn't seem like it even cleared the codes

Rob

 

It needs to relearn the idle. Just give it enough gas to keep it running, and drive it around a bit. (carefully, expect it to stall every time you stop) Eventually, the computer will figure it out.

 

Wow really? I've never had to do this before with any car. This is normal on these trucks?

Rob

 

Check and make sure the cable is back on tight, also check battery voltage. The PCM in these trucks needs and certain amount of voltage to run properly. I think it's 10.5 volts but I'm not sure. Giving it gas causes the alt to produce enough power to keep the truck running.

 

Chevy does that as well. They just aren't quite as obvious about it.

My truck, when I replaced the battery, fired right up, and ran fine right away. But, that was a brand new battery. Don't know if that makes a difference.

You could check the TPS, and verify the IAC is actually doing something.... Probably need a friend to help you do that though.

 

Yes after searching around it looks like the IAC possibly is bad or going bad and the computer was compensating for it and would now need to relearn. Seems like somewhat of a common issue after unhooking the battery.

Rob

 

Perfectly normal. Run the truck as long as it takes to idle on its own.

 

yep had to do it on mine too...more than once when I had a slow drain on the battery killing it if it sat a few days...

 

Mine doesn't do that when I pull the battery cable. When I reconnect the battery, I start it up and it idles just fine.

 

It's not just pulling the cables that cause this, but rather how long the PCM goes without power. Eventually it will lose the idle strategy and it has to be relearned.