low idle.....

[charlie_the_tuna]

so I go out to start my truck yesterday and there's not enough battery to turn it over, so I throw it on the charger for a half hour and it starts right up. only now it's idling at like 400 rpm. what gives??? should I raise the idle or will it come back?? ferm? spare?
2002 gmc Yukon xl 6.0

[THEFERMANATOR]

For starters, you can't raise the idle speed without pissing the PCM off. Chances are you need to disconnect the battery for 30 minutes and let it reset. When the battery goes dead and you charge it with a charger, it can throw the adaptive memory in the PCM off and cause all kinds of wierd idle issues as well as not running right.