'02 Trailblazer needs to be jumped after sitting for a couple of days.

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! Sounds like your Trailblazer has a slow drain or a weak connection somewhere. Since you’ve got a new battery and alternator, I’d start by checking the battery terminals—make sure they’re clean and tight. Corrosion can cause just enough resistance to make cold starts miserable. If that checks out, you might have a parasitic drain. Try disconnecting the battery overnight and see if it still struggles in the morning. If it cranks fine, something is slowly draining power—common culprits are aftermarket accessories, a faulty module, or even a stuck relay. A shop can do a parasitic draw test to track it down. If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554.