Just had my truck (2004 duramax LB7) in the shop for a no start while cold. They let it sit for 5 hours at -20degC then started the truck no problem, not plugged in. charged me an hour's dianostic time (140 dollars) and found the batteries failed. L was 12.31volts, 503 cold cranking amps, R was 12.3V and 434 cold cranking amps. Dealer wants over $450 for two new batteries plus install costs. Anyone know how out of spec these number are? Would this be enough the cause the truck not to start below -10degC? Seemed to turn over fine when cold but its my first diesel so I have no clue if that is a good cranking speed or not. No codes or problems with the glow plugs. Injectors were replaced less than 3 yrs ago and less than 60,00kms ago under warranty. Can anyone recomend a better place to buy batteries? I've had such bad luck with dealers and overpriced OEM stuff that I figure there must be a better option.