We just published a full guide and video on diagnosing parasitic battery draws across GMT400, GMT800, GMT900, and K2XX trucks — covering letting your modules go to sleep before testing, pulling fuses one at a time, checking for failed alternator diodes, and known issues like GMT800/900 instrument clusters and K2XX door harness pinch points.
Read it here: How to Find a Parasitic Battery Draw on GMT400, GMT800, GMT900 & K2XX - FullSizeChevy.com
If you’re fighting a draw, fill out the template in the post above and reply here with your details — year/make/model, engine, platform, battery age, alternator test result, measured draw, fuse that drops the draw, aftermarket accessories, and recent repairs. Photos of your battery wiring and fuse panel help a lot too.
A few things worth checking first:
- Did you let the truck fully go to sleep (doors closed, key out, 30-40 min) before measuring? A lot of “huge draws” are just modules that haven’t timed out yet.
- Pulled the fuse for any aftermarket remote starter or alarm?
- Checked both the underhood AND interior fuse panels?
- Tested whether disconnecting the alternator’s main lead drops the draw (possible bad diode)?
- Got a trailer harness or hitch-mounted brake controller? Corroded trailer plugs are an easy thing to overlook.
Post your results below and let’s get these batteries sorted out.