Why Can't I Retreive DTC CODES????
 

I am not sure why but when I hook up my code reader to my 2002 Avalanche my code reader is not communicating with the truck.
It works fine on my Sierra HD2500.
When I hook it up it turns on,which is what is supposed to do,then I turn on the ignition,turn on my retriever and it just turns off instead of reading codes.
Is there a fuse for the line?
Any help will be greatly appreciated...

Cheers,
Dave

Yeah check your fuses...there is one that controls that I can't remember off hand which one, but just check them all.

Thanks....I'll have a look at those tomorrow.

I know it's old but someone coming along with the same problem might be helped.

The accessory fuse for the cigarette lighter is usually the one that the ALDL is on. If you've done something to blow that fuse by plugging in something too big or dropped something into the socket and blown the fuse the ALDL will have no power to supply the code reader and the code reader will be unable to link.

Many thanks for this advice. I tried to hook up OBDII reader yesterday and nothing would display like no power. I wondered the same thing and after reading this suggestion I remember blowing a fuse with the cig lighter socket using an air pump. Never fixed it because I have like three sockets to choose from. I will now know what to go look for and hopefully will fix my problem for the code reader.

I know this is an old thread but in case anyone does a search and finds this, it was a blown fuse for me on the cig lighter.
... And yes this fixed my problem and we were able to use the OBDII code reader.
... The fuse box for this fuse was under the hood next to the battery.
... My 2002 Silverado has three fuse box panel locations... Under the dash near driver, end of dash between the door on driver side and the one under the hood.
Check your manual if you still have it.