I have a 06 Chevy Tahoe that is experiencing parasitic drain.  Has happened twice before, and I thought it was battery related.  But have been doing more research and convinced that something is draining it.  The current battery was put in in May '11.

There were service bulletins for 03 and 05 tahoes, but not the 06.  It relates to reprogramming the BCM...is this something that has to be done at the dealer only?  I am wondering if mine needs this since my specs are the same as both the 03 and 05 models, and the symptoms are the same as well.

I think you meant ECM instead of BCM

If it deals with the ECM sometimes you have to take it to the dealer so they can use their fancy computer to try and fix issues like that. Other times a regular garage will have about the same computer to hook up to it and see what they can do. However, if it is a relatively common issue then I would take it to the dealer because they may have already fixed that particular issue with other customers vehicles and have experience doing so.

Something else to think about is your alternator. If it is bad it will drain your battery faster than you can mag dump a pmag. Well, maybe not that fast, but fast enough you can watch your volt gauge go down while driving.

The BCM is a different component than the ECM.  It's quite possible that the op really was talking about his BCM.



 

yep, the reprogramming was on the body control module....

I agree with the alternator. It may have a bad diode or two that's shorted. If you find your battery dead after an overnight park, try disconnecting the bat wire off the alternator, tape or slip a piece of hose over the end of the wire as it's hot so it doesn't ground on something. Of course you'll have to have the battery charged up before the overnight park. Then you can check if it'll start.

How many amps is it drawing when its off?

Or you can use a multimeter and know instantly. No need to play guess and check.

As far as I remember the proper procedure is to check the current draw at the battery and then one by one pull your fuses until you find which circuit is drawing the current. This should narrow it down big time.

you need to start by measuring the drain, A regular old test light in between the negative terminal of the battery and the negative cable,
stab the cable and try not to disconnect the cable with out the test light touching both the cable and the battery as you disconnect it.
will show a approximation of the current. You will need to pull the bulb on the hood and wait about 10 min in a chevy for the computers to power down
bright light is about 150 miliamps plus, a dim pulsing light is usually around 30-60 milliamps.
bright light, dead the next day, dim light 3 days sitting and probably dead.
start pulling fuses one at a time and see whic one kills the light. first out under the hood then move to the drivers door.
take a small screwdriver and close the lock. wait ten minutes, and pull the fuses one at a time from the inside fusebox.
Post or PM the results.

I realized that OP didn't say how fast the drain was and the fuse checks is a good idea but some wirings have fusible links instead.

The drain is sporadic, due to how much the truck is driven.  It is fine to sit overnight, but if you run the radio with just the ignition on it will drain it enough so that it won't start.  The check engine light is remaining on since I jumped it yesterday, gonna go get the codes read today hopefully.

Ok, so now another component comes into the mix.  I had the codes read at AutoZone this morning.  Both Bank 1 and Bank 2 of the engine (5.3 v8 flexfuel) are running too rich.  My understanding is that the PCM can screw itself up if the engine is jumped, and that a reprogram may be in order as it sees the alcohol content of the gas as too much.  I put a bottle of Lucas injector cleaner in it just in case, as those codes could mean anything from a dirty injector to an O2 sensor that is going bad.

Use a scan tool to perform an Alcohol Content Relearn.
Do not replace any parts.

It is a flex fuel vehicle correct?

8th  spot of the VIN a Z?

You sure it's not the battery? Have you had it tested? Just because it was replaced in 2011 doesn't mean it's not bad. Batteries these days are designed to last 3 years on the lower end. 5 years for a premium battery. Have it tested would be one of the first things I do.



Then find someone thathas a DMM capable of reading current.  Disconnect the positive terminal from the battery. Put the negative lead of the DMM to the positive battery terminal itself then take the red lead of the dmm and attach it to the battery.



Truck like that should read about 80-90ma for the first 2 or 3 minutes after you close the door. Then afterwards drop down to about 40-50ma

did that...and had autozone test the battery...it is gtg.