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2009 CTS
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Discussion Starter #1
Starting a few months ago, the rear door locks on my 2009 CTS starting acting up. They work about %40 of the time. Based on my research, I'm tempted to blame the actuators but what is confusing is that both rear doors either work or don't work together. In other words, if the rear driver side lock works, then so does the rear passenger side. They either both work, or both don't work. If each door has it's own actuator, how can this be? Could it be something else? Thanks.
 

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2009 CTS-V
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Not exactly sure on the coincidence for the doors but I have an '09 and had one door starting it about two years ago. Bad actuators were the key. Dealer replaced both under extended warranty. No problems since.
 

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2009 CTS
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Discussion Starter #3
Not exactly sure on the coincidence for the doors but I have an '09 and had one door starting it about two years ago. Bad actuators were the key. Dealer replaced both under extended warranty. No problems since.
Thanks. Yeah, I was thinking the actuators. I just can't get past the coincidence, though. I mean really...they both work or don't work in unison 100% of the time. Something is fishy with that. I'm going to do a little more snooping before replacing them...especially since I'm no longer under warranty.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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All I can think of is some type of electrical gremlin.
 

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2011 CTS-V wagon
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You might check the voltage when you hit the lock button. If engine is off, it will be around 12.7. If engine is on, it could be anywhere from 12.7 to 15.4. I don't see why it should matter, but something to check.
I'd guess the CAN bus transfers a message to each door module to do lock/unlock. For both modules to act the same seems pretty unlikely. So that would imply it is the message send
not happening, but if front doors are locking normally, then it doesn't seem like a send issue. Are you sure the lock works on the front doors?
 

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cde010 said:
Thanks. Yeah, I was thinking the actuators. I just can't get past the coincidence, though. I mean really...they both work or don't work in unison 100% of the time. Something is fishy with that. I'm going to do a little more snooping before replacing them...especially since I'm no longer under warranty.
Keep your eyes on it. You'll think the car is locked and it's not.
 

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2009 CTS
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Discussion Starter #7
You might check the voltage when you hit the lock button. If engine is off, it will be around 12.7. If engine is on, it could be anywhere from 12.7 to 15.4. I don't see why it should matter, but something to check.
I'd guess the CAN bus transfers a message to each door module to do lock/unlock. For both modules to act the same seems pretty unlikely. So that would imply it is the message send
not happening, but if front doors are locking normally, then it doesn't seem like a send issue. Are you sure the lock works on the front doors?
Yep. The front locks work 100% of the time. And the back locks "flinch" even when they don't work.

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Keep your eyes on it. You'll think the car is locked and it's not.
Yea, I have to double check all the time. Thanks.
 
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