2008 grand prix won't lock!

If the dealer did not check your remote,could be as simple as reprogram your remote or replace it.Other words faulty remote.

Do you know if your car has an aftermarket security system? Or just the factory alarm? In other words, when you set the alarm, do you hear a chirp from a siren or a honk from the horn?

This just happened this winter on my car and I didn't worry because it was only a tiny inconvenience and too cold to play around with. 1/...with all doors closed could lock and unlock with fob or key from outside the car....2/..sitting in the car with all doors closed I could lock and unlock using door switch.....3/... but I was in the habit of opening the driver door and hitting door switch to lock the doors as I got out and that stopped working..... I had electric locks working with key or fob or door switch except for that one method; so it couldn't be a fuse - right( besides there was nothing else not working.) Turns out that even though the electric locks worked in all ways but that one way,and I had dash lights,power windows,map lights,etc.,etc., all working. I found a blown fuse in the trunk . replaced it & thought can't be. It was,back to hitting the door switch as I exit. It's been two weeks and I haven't yet opened the owner's manual to see what else is on that circuit . ..... so check fuses - mine had two fuses to the electric locks..

I have a 2007 Grand Prix with exactly the same symptoms. When it is acting up, all 4 locks will no longer activate with the remote fob, either door switch, or by putting the car in gear. When I try to lock the doors, I do hear a clicking under the dash on the driver's side. The problem is worse when it is warm or hot outside. The un-lock function always works correctly. At first, I was going to replace the lock relay but discovered that there is not one. What I think is that there is a relay but it is soldered to the control module that is under the left side of the dash. My current theory is that it is simply a bad solder joint on that module somewhere between the lock relay and the connector to the body harness. I am currently looking for a schematic of the system to confirm my ideas.

Door locks some time work

Update: I pulled the body control module out to identify the door lock relay and to inspect for bad solder joints. No bad solder joints were found. The relay was a semi custom dual unit. (I was able to find replacements.) Anyway, when I put the module back, I connected and disconnected a few times to clean the contacts. That appears to have solved the problem because I have been a year now with no issues.

Thanks for the update autoX4me . So the relay "pack" is on the back of of the bcm, and you replaced it?

Thanks for the update autoX4me . So the relay "pack" is on the back of of the bcm, and you replaced it?

I was having a problem with my 04 grand prix locks not working. Only one would work, one of others would move up or down a little when I pressed the button, the other 2 wouldn't move at all. I took the 3 actuators that didn't work out because I was going to replace them. Before I spent a lot of money on new actuators, I figured I would by a can of electrical cleaner and see if I got lucky. I sprayed a lot of the cleaner into holes in the actuator. I plugged each one back in to test it and now they all work. One of them is week so I have to press the button twice to lock it but it is better than spending a bunch of money on a new one. Its definitely worth a try

I have 2008 Grand Prix GXP with door locking issiiues same as Arin 43 above. Yes, I did need new key fob, but still wouldn't lock or unlock or remotely start the car. Took in to dealership and diagnosis was that I needed new actuators on all 4 doors to the tune of $1480. Thanks, but No thanks. A friend suggested that maybe the actuators just needed to be cleaned, Thank you Arin 43 for your tips to resolve this issue. I will see if I can find someone to help me take them out and clean them. I only have 61,000 miles on my car and would love to drive it a few more years. I will update with results