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2008 Grand Prix Door lock actuator failure

gerald

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I bought a 2008 Grand Prix (110k odometer) for my grandson and I'm in the process of clearing up minor mechanical issues. I bought it from an individual and didn't notice that all four doors have locking/unlocking issues (manual & remote). I noticed that some of the doors would lock/unlock some of the time but not one of them worked every time. Most of the time they moved a little but not enough to lock/unlock.
I bought two new remotes on eBay for $18 and carried them to the Chevrolet dealer to have the programmed ($45 for both). While I was there and thinking there might be something wrong with the BCM, I had the service dept check out the door locks. They advised me that all four locks were defective. I was still afraid to buy them all, so I bought only one for the left rear door to install myself. After installation it worked perfect. I ordered the remaining locks online at GM Parts Headquarters and saved almost $200.
Unlike older vehicles with separate actuators, this model has actuators built into the lock itself as one assembly with a 6 pin connector (only five pins used). I had already looked up the connector and found 12v was applied on pins 2 & 3 (Pin 1 not used) to lock and reverse the polarity to unlock. There were screws that hold the cover on the assembly but there was a metal back-plate with two rivets that kept me from taking it apart. I was surprised when I drilled out the rivets from the backside (not the striker plate side) and discovered a small motor with a worm gear drive. By the way, The back-plate can be reinstalled by drilling the shouldered rivet post and tapping for an 8-32 screw. The mechanism was free and worked smoothly so the problem has to be loss of power in the small motor. The motor actually run without a load when I applied 12v to it. The motor body is about 1 1/4" long and 3/4" elliptically shaped.
My question is, has anybody had this much trouble with the door locks on Grand Prix's? Also, does anyone know if there is a replacement motor on the market that will fit these locks. There are several styles of actuator motors for sale on eBay for about $6 but none of them are identical to mine.
It wont help me much this time around but there must be a lot of people out there that don't have $500 to spend on parts alone when they can be repaired for less than $10 each.
 
G

G-343333

Gerald,

What did you end up doing? I have this same issue with my 08. I thought it might be the BCM as well.

Thanks,

Adam
 

melsg5

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OP hasnt been on this site since 2013
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08GrandPrix

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Gerald,

What did you end up doing? I have this same issue with my 08. I thought it might be the BCM as well.

Thanks,

Adam
I have a similar issue and unfortunately found out it was NOT the BCM. I was so sure that was the problem that I bought a new AC Delco BCM and had the local dealership swap and program it.
Afterward, same problems.
When I get in the car after leaving it for several hours (morning, after work), it'll usually unlock all 4 doors. But if I try to lock them, they'll all make a weak noise and none will lock.
BUT, when I put it in reverse, all the locks lock, every time.
All that seemed "obviously" the BCM, but no, several hundred dollars later, a new BCM did not fix the problem.
 

melsg5

Staff member
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Would you consider having the dealer diagnosis and fix the problem? It appears you are stating manually trying to lock the doors with the interior switch does not work which would make me think you have a bad switch.
 

cammerjeff

Member
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Belleville MI
It looks like the front actuators are still available, even rock auto has them, the drivers side is around $50.00 from them and seems to include the latch assembly, the passenger side is just the actuator at under $15.00
 
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