2003 Chevy Impala wont start

sounds like your not getting any power from battery at all, who ever replaced the starter didn't connect your cable from battery correctly. one hot cable runs from battery to starter , you can start there, check battery and fuse, in not a mechanic, but I've changed a few starters on Chevy truck, hope this helps, good luck!

Chevy Impala 2008 won't crank and won't start, fix found ...

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https://www.youtube.com/watch?v=ITvU_vXMrDY
Nov 26, 2012 - Uploaded by Artome001
Chevy Impala, 2008, does not crank or start. ... 2003-2007 Chevrolet/GMC Silverado/Sierra No Start/no crank/electrical issue FIX - Duration: ...

2006 Chevy Impala / MC No Crank/start FIXED - YouTube

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https://www.youtube.com/watch?v=dGF0Ohbj5xg
Jun 8, 2015 - Uploaded by Jair Duarte
2006 Chevy Impala / MC No Crank/start FIXED .... 2003-2007 Chevrolet/GMC Silverado/Sierra No Start/no crank/electrical issue FIX - Duration: ...

Passlock Security system... - Discussion on Topix

starter solenoid got short to ground,it is probably stock,tap it lightly with hammer,if it works,after that go ahead and get new starter

I sounds like you have a fuel flow problem. Replace the in-line fuel filer located in the fuel line in front of the rear tire. Check out this web site for "how to" replace the in-line fuel filter.
http://www.ehow.com/how_6724057_install-filter-2003-chevy-impala.html

I was told u cant bypass security light - it may be a broken wire or a wire came off starter or it could be the key switch - mine would do that - leave key in the ignition (may have to leave ignition on) for any where from 11 - 30 minutes and see if it starts then - if it does I had to have the ignition replaced and there is a recall on those for that - it costed me $605 to get it fixed - waiting to here back from Chevy about getting reimbursed for it!

Check antitheft or aftermark inmobilizrer there.

You mean the engine dosent turn or the engine dont start. If it dosent turn then try to turn it manually by a socket and ratchet in the crank pully bolt, I have changed the starters only to find out the engine is seased.

remove and clean the battery terminals ,

neutral safty switch is out of adjustment!!!

Sounds like the neutral safety switch is faulty. Slamming the shifter into Park has temporarily solved the condition for some, but the switch may have to be replaced.