How do I change the ignition key lock cylinder on a 2009 Chevy Aveo? Does it have to be recoded?

Yes anti-theft system and immobilizer lockout. Number one tip, always keep voltage to the ECM using wires or jump leads to the starter motor or the battery leads..

https://www.google.com/search?q=2009+chevy+aveo+reset+security+system

You may have a bad sensor or a problem. that needs attention.

is the indicator in the park position really in park ? was the replacement cylinder installed properly? could it be hanging up on locking in steering collum .? try moving steering wheel hard left and right while trying it remove key.

Sounds as if you may have blown fuses or stuck relay.

Electronic Park Lock (EPL)/Ignition Lock Cylinder Control Actuator: If the vehicle is equipped with automatic transmission and a floor mounted console gear shift, it has an ignition lock cylinder control actuator system in the steering column. The ignition lock cylinder control actuator purpose is to prevent the ignition key from being turned to the OFF position when the transmission is in any position other than PARK and the vehicle may still be moving. The column ignition lock system consists of an ignition lock cylinder control actuator, and a park position switch that is located in the automatic transmission shift lock control switch. The ignition lock cylinder control actuator contains a pin that is spring loaded to mechanically prevent the ignition key cylinder from being turned to the lock position when the vehicle transmission is not in the PARK position. If vehicle power is lost, and/or the transmission is not in the PARK position the operator will not be able to turn the ignition key to the lock position and will not be able to remove the ignition key from the column.

Does your impala have floor shifter ?

FYI this is now a free dealer fix--Service Bulletin--not a recall. chevy sent letters reregarding issue. Mine was the lock cylinder housing was faulty, the piece that holds the springs to the pieces in for the key shape poped out. temp fix is you can unplug wiring harness under steer wheel to disable the car and remote will still lock door and alarm still works. Of course mine went out on a saturday afternoon. you can remove the lock cylinder yourself and take to locksmith, they can fix the cylinder probably for under 10 bucks. i luv it a 16000 car stuck because 1/8" by 1/2" piece of metal comes loose.

I would have gotten a locksmith to remove the old key, its cheaper than a new cylinder, plus you need to install it.

There is a TSB on this issues if your having ignition lock issues.
Service Information
2009 Chevrolet Cobalt | Cobalt, G5 (VIN A) Service Manual | View All Bulletins | Document ID: 2325129
#09-02-35-005: Ignition Key Difficult to Remove, Ignition Key Binds or Sticks in Cylinder (Replace Ignition Cylinder) - (Aug 10, 2009)

Subject: Ignition Key Difficult to Remove, Ignition Key Binds or Sticks in Cylinder (Replace Ignition Cylinder)

Models: 2008-2009 Cadillac CTS (Built Prior to VIN Breakpoint 90163371)

2005-2009 Chevrolet Cobalt (Built Prior to April 14, 2009)

2006-2009 Chevrolet HHR (Built Prior to April 14, 2009)

2007-2009 Chevrolet Equinox (Built Prior to July 2008)

2005-2006 Pontiac Pursuit (Canada Only)

2006-2009 Pontiac Solstice (Built Prior to April 14, 2009)

2007-2009 Pontiac G5 (Built Prior to April 14, 2009), Torrent (Built Prior to July 2008)

Attention: This bulletin only applies to vehicle equipped with automatic transmission.

go to link the year is diff but the procedure is the same. scroll to bottom of page

http://www.2carpros.com/forum/1994-chevy-s-10--ignition-lock-cylinder-vt197051.html

Add Duplicate Key (PK3 or PK3+ key)
1. Insert an existing working key into the ignition cylinder.
2. Turn the ignition cylinder to ON (RUN) and back to OFF.
3. Remove the existing key and, within fifteen seconds, insert the new key
and turn it to ON (RUN).
4. The security light will light up for two seconds to indicate success in programming
the key into the vehicle.