Dose the same key start the car and unlock the doors on an 04 cavalier? the key i have does not unlock my car?

sorry most of the cars ive had need two keys but some only have one but since you key dont work then try it in the trunk and then it could be that the switch has been replace and that key only fits the switch

l cant say for certain but most cars are like that now.the days of a separate key for the trunk and doors are long gone. I'd be willing to bet it does.

Sometimes, the key wears over time in such a way that it works better in certain parts of the car, usually the parts it is most often used in, like the ignition switch. Try having a new key made, but NOT by the hardware store, have a GM or Chevy dealer get original key number, this is usually on the passenger is side door lock assembly, (putting on the key itself is no longer legal) and have them cut a fresh key based on that number, that key should work all locks

l think it does have the same key for ignition & the door- the lock on the door may have been replaced or the ignition lock may have been replaced & instead of re keying the lock they had one precut & keyed- u might need to get a locksmith to make a key, either that or u can buy the lock cylinders & have them keyed to match the ignition lock. some parts guys that have had many years of experience can tell the key code just from looking at the key. u could have a worn out key too, try getting it re cut at a chevy dealership.