* Radio Code: This is the most common issue. After disconnecting the battery, your radio may require you to enter a security code to reactivate. This code should be in your owner's manual or possibly on a sticker inside the glove compartment. If you can't find it, you may need to contact a Chevrolet dealership with your VIN.
* Clock and Other Settings: The clock and possibly other settings (like your seat memory if equipped) will likely reset to default. You'll need to readjust these manually.
* Power Windows/Seats (Rare): In some rare cases, the power window or seat memory settings might need to be re-learned by cycling the switches a few times.
* Check Engine Light (Unlikely but Possible): While unlikely from just a battery change, a temporarily disrupted electrical system *could* trigger a check engine light. If this happens, you may want to drive the vehicle for a while to see if the light goes out. If it persists, have the system scanned for trouble codes at an auto parts store or mechanic.
In short: Replacing the battery in a 2003 Avalanche is a relatively straightforward process. The main thing to be aware of is potentially needing to enter the radio code. Other minor settings may also need readjustment. If you encounter any persistent issues after the battery change, consult your owner's manual or a qualified mechanic.
