2009 sierra denali electrical help please

boilermakermock · June 28, 2013

I just got this truck yesterday and idk whats going on. The cd scanner will randomly scan with no disc in it. No keys in and its shut off. The lights are set on auto amd stay on all day. While driving at night the gauge cluster will dim then brighten. If its dim and you turn it up nothing happens. If its bright amd turn it down nothing happens. I replaced the alternator thinking that was the problem and it wasnt. Theres nothing blocking the sensor on the dash either. Need some help bad cuz its annoying to be driving then blinded by your dash lights. Truck is a 2009 1500 awd denali with the 6.2 liter flexfuel

ujtruck · June 28, 2013

please don't think your alternator is bad, you have to test it.

blocking / unblocking the sensor will not tell you it is a bad sensor, did you measure its resistance ?

boilermakermock · June 28, 2013

I did test the alternator. It was bad so thsts y I replaced it but still didnt fix the cluster lights. And idk how to measure the resistance of the sensor. Besides tearing the dash apart.

gmtech4 · June 28, 2013

,where did you buy the truck ? did you call them and ask WTF ?

oldscsc · June 29, 2013

Is the battery original? I'd be taking a look at and testing it.

ujtruck · June 29, 2013

yeah; before you troubleshoot this thing, you must call that guy and ask, as per Rob what the ???k

ok alternator bad, was it producing over voltage? if yes

then you have to check BCM (Body control module), you will need a DVM, nice Test light etc... to find out whats going on. it could be even loose wire (ground),

what else ? is your power windows working ok?

or take it to a Qualified electrician

boilermakermock · June 29, 2013

No it was under voltage. Yea power locks still work and windows. I work 13hrs on nights 7 days a week. I dont got much time to crawl around and look for ground wires so where r they putting those now days. Im an old chevy guy not to much into wiring

txab · June 29, 2013

As mentioned, check battery. Check both battery connections. Clean and tight. There have been a few members actually have battery cables that went bad internally. Check body grounds