The power door locks do not lock all the time in my 2007 Pontiac Grand Prix GXP. They are intermittant. The UN-lock works good. Locking sometimes fails when: Putting the car into gear; Pressing the lock button inside the car; Or, pressing the lock button on the keyfob. Note that when using the key fob, the horn blows indicating that the alarm set but, the doors don't always lock. The problem is occuring with all 4 doors. I am assuming that the lock relay needs to be replaced but, I don't know where it is. Can yo help?

SOURCE: power lock wont lock door on 99 grand am will only unluck them.

it is more than likely your buttons, if one button is bad neither will work.

Try changing the buttons, if that does not work, then it could be one of the motors,
same as the buttons if one is bad neither will work.

to change the buttons, simply remove the screw on the panel, if there is one, if not then insert a small flat head screw driver on the bottom of the panel and gently push down this will pop the panel out.

once you get it out pull the plug off, there is 2 8mm screws holding the switch in, then screw your new one in and plug it back in, do the same on the other side. the panel will just snap right back in.

If this does not work, check the motor, you have to remove the door panel, then the silencer pad, once you get in, it will be inside the door near the back. about half way down, it is round with a rubber boot, it is held in with some rivets. If you need to replace it you will have to drill them out, and replace with nut and bolt.

To test it, if you have a corless drill... pull the plug from the motor, and stick 2 wires into the plug, one for positive and one for negitive, and touch the ends to the battery. if it does nothing then it is your motor, but make sure you switch the wires from one side ot the other to test both up and down.
One wire is for up and one if for down.

If you do not have a cordless drill battery just use long peices of wire and use the car battery.

Don't worry there is not enough power in a car battery to shock you.

SOURCE: 2004 Pontiac Grand Prix: Just started having

These cars have a body control module which could be faulty,have a mechanic check this out.

SOURCE: I own a 2006 Pontiac Grand Prix and the key fob

i had the same thing happen to me i just replaced the battery the had it reprogarmed. by a pontiac dealership mechanic

SOURCE: key locked in 2001 pontiac grand prix battery is

lock smith or someone authorized to use a slimjim[can do more damage if dont know how to use ]--or-- key fob wont work if vehicle battery dead if u can reach up under car at front and release hood latch then jump battery and then use key fob to unlock door

Testimonial: "thank u"

SOURCE: my key fob will only unlock, pop my trunk and set

You need to replace the FOB. I had the same problem. The contact points under the touchpad go bad. Find a local locksmith to proagam the FOB you will save about $40.00 compared to the dealer.