I changed out ignition and my car won't start and the transmission light is on. My car is a 2007yukon .

Automatic has a shifter switch to assure you're in park or neutral. Clutch on stick shift has a switch too.

hi there.
this youtube video might help you out.
NISSAN MICAR k12 WON START OR TURN OVER RANDOM PROBLEMS WITH IGNITION
or this google link.
Nissan micra k12 won start Google Search

Ignition switch was my problem after changing fuel pump and main relay. Then had to have transmission rebuilt, all of this was back to back.

For car not changing gears and not shifting out of park mode ,it can be shifter assembly issue, or it can also be transmission issue. Get the shifter assembly inspected with ignition OFF.

For more troubleshooting, I suggest you to get the Following help link checked, its complete step by step procedure to inspect gear shift issues: -----

GEAR SHIFT ISSUES

http://alltypesofpartsreplacing.blogspot.com/2012/11/gear-shift-issues.html

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NO REVERSE ON TRANSMISSION
http://alltypesofpartsreplacing.blogspot.com/2012/12/no-reverse-on-transmission.html
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Transmission fluid leak, transmission gears slip,
http://alltypesofpartsreplacing.blogspot.com/2012/12/transmission-fluid-leak-transmission.html
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These will help.

Thanks.

engine size, etc., I can only make educated guesses, but here goes: You stated "My car will drive, but very slow hardly moving". My first suspicion is that you don't have a transmission problem, but the car is in what Chrysler calls the 'limp-home mode'. This occurs when the computer 'sees' a problem with an engine function or sensor that is serious, but not so bad that the car won't run at all. Limp-home mode allows your car to only operate in second gear so that you won't damage it further by driving normally, but won't leave you stranded either. Is your 'check engine' or 'service engine' light on? If not, check to see that it actually works by turning the key 'on', but not starting the car. All the dash lights should be lit for about 3-5 seconds. No matter what, you need to check your transmission fluid level (on a Crysler, should be checked with the engine running and in gear, NOT park or nuetral). Safety first, make sure someone is holding the brake on - please don't ever trust a 'parking brake' for this. If the fluid level is OK and there's no 'check engine' light you need
to visit a competent transmission shop. Probabably a worn front pump, torque converter, or a hung spool valve in the valve body, none of which is generally fixable at home. If you do have a 'check engine' light on, see a regular mechanic first as there is a mechanical problem probably not related to the transmission. Good Luck!

Could be several things that caused car won't start, inculding starter, ignition, dirty or loose battery connections.
Honda Diagnostic Tool

Not sure if I read your post right, but you have to have a hot wire to the ignition switch from the battery, independent of anything else on the car, before the switch will work.
The CPS is a common problem on the jeeps, though. If bad, you may not get a coil signal.

If it is a 3.8 engine change the crank sensor,they go bad on the 3.8 engines.

Done cars have a kill switch if they are low on oil. Check your oil. If the oil is good, it may be the ignition switch.

you can not bypass the security in that car, it is built into the main computer, they have problems with the ignition switch screwing up and the only way to start it while the light flashes is to turn the key to ON but don't crank engine, leave on for 10 to 15 minutes until light goes out then start car.