Been doing a lot of research on this and cannot find what I'm looking for. Very cold yesterday, about 3 above. Got in the Sierra at one point and "click, click, click". The battery didn't seem dead but it would not start. Got a jump, got it home, the positive cable was badly corroded. Cleaned it, still would not always start. We found if we wiggle the positive cable we could get it to start. Did some more cleaning and made sure the positive cable was tight. Seemed OK. Later in the day it didn't start again, then went into limp mode (NOT fun!). I got it home and checked the code, P0606, power train code, inferring a problem with the PCM. Shut it off, started it again and the code was gone. Got it in my dad's garage (he has heat) and tried a spare battery. The positive post on the old battery has a little back and forth movement which could explain why wiggling the cable got it to start. That battery tested at 12.7 volts. The spare battery tests at 13.8. Also the voltmeter on the truck was way over 14 with the old battery. It's just a little over 14 with the spare. With the spare battery everything seems fine now. So here's my question, I thought I've read that a bad battery can cause the PCM to wig out. I know it can happen with a bad alternator. Am I on the right track here? I'd hate to buy a new battery and find out I still need to looking at something else. Thanks!