The battery went out in the key fob. I changed it and now my 2005 Pacifica wont start. It displays invalid key fob. I checked the car battery, tried unplugging it to reset everything. A friend of mine check the computer system and it said code: po513. Anyone know what it could be. Father of four so i cant afford to buy a bunch of parts for trial and error.

 

Looks like an immobilizer fault to me, the chip has probably become de-programmed in the fob when the battery went out. Does it start ok with your spare?

https://www.obd-codes.com/p0513

If you have a key working, this video may help it's for an older Chrysler but could be worth a go

 

Sounds like this may be your only key?? If so you'll have to have it reprogrammed by a dealer or a locksmith. Does your key have a circuit board inside with a microchip on it? I have seen older keys that actually have a small device inside them that can fall out. If you're not careful opening it, it can fall out and you may never know it. It's a very small capsule shaped thing and if it fell out the key will not be able to be programmed without it. If this is the case you will need a new key to be programmed. If your key has the circuit board with a microchip in it it won't have anything inside that can fall out and you will just need to have it reprogrammed. They don't normally need to be reprogrammed because of a battery change but it can happen. I would recommend that you get a couple keys for the vehicle. Once you have 2 working keys you can easily program a 3'rd or 4'th yourself. You can get a complete key FOB (ready to be programmed) on ebay for under $20. Have it cut at a hardware store and program it yourself once you have 2 working keys. Just make sure to get a key FOB with the same numbers that are on the back of your current key because there are different types. The numbers are stamped on the back of the key.