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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #1 ·
I've read a few of the door microswitch threads, but I think there is also the possibility of electromechanical lock actuator malfunction. I would like to diagnose this behavior: intermittently, both rear doors appear not to electrically raise the rear lock pull knobs. Pulling the driver door or front passenger door handles causes a solenoid sound, but the raising of the rear lock knobs seems to be intermittent. Manually raising the affected rear door lock knob of allows the outside rear handles to open the doors. I guess I haven't been checking to see if the rear doors are actually locked when I walk away with the keyless fob and the car locks itself.
 

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2009 CTS4 Premium & 2021 Blazer 2LT
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825 Posts
Intermittent unlocking electronically (buttons or fob) but consistently with manual knob indicates the actuator needs replacing.
 

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'12 CTS Performance Sports Wagon AWD
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The rear doors also have microswitches. I had to replace both front doors and the rear door on passenger side within 2 weeks of each other. The rear door has a switch in it that unlocks all 4 doors but it mechanically opens. The front doors on the keyless start cars have 2 positions. One unlocks the door(s) and the other releases the latch. On key starts the front doors are similar to the rear doors and only unlock the door requiring the door to be mechanically opened If I recall properly. (Coupes may work differently.)
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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The rear doors also have microswitches. I had to replace both front doors and the rear door on passenger side within 2 weeks of each other. The rear door has a switch in it that unlocks all 4 doors but it mechanically opens. The front doors on the keyless start cars have 2 positions. One unlocks the door(s) and the other releases the latch. On key starts the front doors are similar to the rear doors and only unlock the door requiring the door to be mechanically opened If I recall properly. (Coupes may work differently.)
No, misinformation...
Sedans and wagons


The driver and front passenger power door lock switches are integral components of the driver door lock/window switch and passenger door lock/window switch. The switches consist of 2 positions, lock and unlock, and are in the normally open state. When placed in either the lock or unlock positions, the switches provide a direct input to there respective door control module. When a power door lock switch is operated to the lock or unlock position, the associated door control module responds by sending a serial data message indicating a change in the switch's position. This serial data message is received by the opposite door control module as well as the BCM. The driver door lock/window switch and passenger door lock/window switch respond to the lock/unlock request by activating there associated power door lock motors to the appropriate direction to lock or unlock the front doors. The BCM is responsible for controlling the left and right rear passenger door lock motors. The BCM, upon receipt of a lock or unlock serial data signal, will control either the rear door lock or unlock relay. When the appropriate door lock relay is energized, the rear power door lock motors will lock or unlock the rear doors.

Power Door Lock and Unlock Switch Operation (Coupe)

The driver and front passenger power door lock switches are integral components of the driver door lock/window switch and passenger door lock/window switch. The switches consist of 2 positions, LOCK and UNLOCK, and are in the normally open state. When placed in the LOCK position, the driver door lock/window switch and the passenger door lock/window switch will disable the interior and exterior door handle switches preventing the doors from being open. Pressing the UNLOCK position on either power door lock will enable the interior and exterior door handle switches providing normal door opening and closing operation.

Power Door Lock Deadlock Motors

Some vehicles may be equipped with the deadlock feature, which includes a reversible deadlock motor contained within each door latch assembly. Each deadlock motor is wired to the lock and unlock relays through 2 control circuits; the door lock actuator lock control circuit and the door lock actuator unlock control circuit. To deadlock a door, the door locks are activated by momentarily supplying voltage to the door lock actuator lock control circuits, and ground to the door lock actuator unlock control circuits. The voltage to the door lock actuators is provided through the normally open switch contacts of the theft deterrent alarm relay. To complete the deadlocking, the theft deterrent alarm momentarily energizes an internal relay causing the switch contacts to close applying voltage to the deadlock actuator control circuits for both front and rear doors. Ground to the deadlock actuators is provided through the door lock actuator unlock control circuits. Once the doors are deadlocked, the mechanical lock/unlock linkage within the door lock actuator is physically disconnected so that the door can not be opened even when manually unlocked. If the content theft feature is armed at the same time, the interior door lock switches will not operate the locks.

To undeadlock the doors, the BCM unlocks the doors by momentarily applying ground to the deadlock motor unlock control circuit. This energizes the rear door unlock relay coil causing voltage to flow through the switch contacts to the door lock and deadlock motors. Ground for both motors is supplied through the door lock motor lock circuit through the normally closed contacts of the lock relay to ground.

Driver Door Key Cylinder Switch

The vehicle may be equipped with the central door unlock feature. With this feature, all doors can be unlocked from the driver door using the door key. To operate the feature, the door key is inserted into the driver door lock cylinder, turned to the unlock position and held for 3 seconds or longer, or turned to the unlock position twice within 3 seconds. A mechanical linkage rod connects the driver door lock cylinder to the key cylinder unlock switch, which is built into the driver door latch assembly. The key cylinder unlock switch contacts, which are normally open, receive a constant ground via the ground circuit. When the door key is turned to unlock, the switch contacts close and the driver door lock/window switch detects a switched ground. The driver door lock/window switch sends a serial data to the Remote control door lock receiver, indicating the key cylinder unlock switch request. The remote control door lock receiver is the master of all lock and unlock operations. If the remote control door lock receiver determines that the key cylinder switch request is valid and conditions are correct, a serial data message will be sent to the driver door lock/window switch, passenger door lock/window switch, and BCM to lock or unlock there respective doors.

Passive Keyless Entry System Description and Operation

Passive keyless entry allows entry to a locked vehicle without pressing any buttons on the keyless entry transmitter. You must only have the transmitter with you. This passive system is also part of the vehicle starting system. It allows you to start and run the vehicle having only the transmitter as your key. The passive entry and starting system use low frequency antennas in several different areas on the vehicle to determine the location of the transmitter. When passively opening a locked door, trunk or the liftgate, you must have a programmed transmitter with you in your pocket, purse, or briefcase. As a customer opens the door handle or presses the trunk/liftgate touch pad, the low frequency antenna sends out a challenge to the keyless entry transmitter. The transmitter should be in a one meter range of the door or trunk/liftgate in order to receive the challenge. If the challenge is met, the transmitter will respond, allowing the door to be unlocked and opened by pulling the appropriate door handle or allowing the trunk/liftgate to open by pressing the touch pad.
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #5 ·
No, misinformation...
Sedans and wagons


The driver and front passenger power door lock switches are integral components of the driver door lock/window switch and passenger door lock/window switch. The switches consist of 2 positions, lock and unlock, and are in the normally open state. When placed in either the lock or unlock positions, the switches provide a direct input to there respective door control module. When a power door lock switch is operated to the lock or unlock position, the associated door control module responds by sending a serial data message indicating a change in the switch's position. This serial data message is received by the opposite door control module as well as the BCM. The driver door lock/window switch and passenger door lock/window switch respond to the lock/unlock request by activating there associated power door lock motors to the appropriate direction to lock or unlock the front doors. The BCM is responsible for controlling the left and right rear passenger door lock motors. The BCM, upon receipt of a lock or unlock serial data signal, will control either the rear door lock or unlock relay. When the appropriate door lock relay is energized, the rear power door lock motors will lock or unlock the rear doors.
In spite of the massive amount of pasted Alldata text, I don't actually see anything pertaining to the rear electric lock actuators. From observing slight movements in the upward direction this morning, it sure does look like the electric lock actuators are weak. Which is a strange state of an electric solenoid, causing me to suspect possible mechanical stickiness.

I can't think of how this would be a microswitch issue. When I pull the driver's door handle to the first position, triggering passive keyless unlock of all sedan doors, the actuators try to unlock. They just fail much of the time.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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Its scattered in there. Your back doors are both mechanical and electronic. If both the doors are having the issue of the locking mechanism not doing what it should that would lean towards bcm territory. To help me try and peice my thoughts back together,you have the keyless entry correct? if you pull the driver handle with keys in pocket when the back doors fail does the passenger door unlock, or make the unlocking sound?
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #7 ·
Yes, if you read my post your questions were answered already.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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Deleted? Does not mention the passenger door, ive read it twice. But, I am sleep deprived. My issue that I 2as having with my locks was a lose pin at the bcm. I took my meter to ever actuator and switch. It was miserable . I used this video as a reference to test. Its not a walk through for your issue but it helped me a lot since I just got the car in October.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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The dts forum with your oriblem description ended with this
"The power lock actuator is built into the door latch. Spray WD 40 in the latch and manually lock and unlock the doors. Sounds like the back doors were never opened. I would say you're getting power to them because you can hear them engage. Hope it's an easy fix. The latch lock compo isn't that expensive and readily available if needed"
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #11 ·
Deleted? Does not mention the passenger door, ive read it twice. But, I am sleep deprived. My issue that I 2as having with my locks was a lose pin at the bcm. I took my meter to ever actuator and switch. It was miserable . I used this video as a reference to test. Its not a walk through for your issue but it helped me a lot since I just got the car in October.
When I pull the driver's door handle to the first position, triggering passive keyless unlock of all sedan doors, the actuators try to unlock. They just fail much of the time.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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Proof positive, drugs are bad. Especially the prescribed ones. I was better off as a teenager at the street pharmacy 😖

.....I found it, yeah, the dts fix?
 

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Discussion Starter · #13 · (Edited)
Proof positive, drugs are bad. Especially the prescribed ones. I was better off as a teenager at the street pharmacy 😖

.....I found it, yeah, the dts fix?
Maybe. I looked at the parts catalog, and found a lock and cable assembly for $113 (passive entry with theft deterrent version) that shows the solenoid is remote to the lock, working through what I am guessing is a push/pull cable. Given the cable involvement I'm not optimistic about the schmutz-spray approach, although this is often appealing for it's ease and low cost. Until the problem recurs.

Looks like a $300 fix even if the diagnosis is correct. While the rear doors aren't used as often as the front, the locks are locked/unlocked daily as part of keyless vehicle entry, so I don't think this is a case of lack of use.

I'm guessing the cable is getting sticky, and getting a new one means getting a new door latch as well. While I suspect it is possible to disassemble, clean and re-grease there could be some wear involved as well. I'm all for saving $$, but I appreciate even more only doing the job once.
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #14 ·
Now that I think about it, there may have been a few occasions where the front passenger side door didn't unlock at the first tug of the front driver's door handle, or push of the unlock button on the remote. I'll have to pay closer attention and see if the either of the front door lock mechanisms are becoming unreliable as well. For now I think I'll replace both rear door locks and cables, as the evidence is pretty strong. Particularly when I looked at the left rear door lock knob this morning as it weakly attempted to push up with the front driver's door handle microswitch. Sure sounds like a sticky cable.
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #15 ·
The child locks are already disabled, thanks. A pair of locks and cables for the rear doors have been ordered. Last night I activated the electric unlock three times on the left rear door. Each time the lock knob moved up a couple millimeters until the third time when it fully unlocked.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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Its possible that the cable being "sticky" could have lead to the actuators demise from being stressed. Everything you mentioned in the last posts make a pretty solid case for your remedy. Hopefully the passenger door is operating normally. If it has been wearing down also that would point towards the central locking mechanism would it not?
Mine seems to be working after fixing the connection issue at the BCM in the X2 connector if I remember right, but after reading this I will be paying better attention. Fingers crossed to not have to reference this information soon
 

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Discussion Starter · #17 ·
Hopefully the passenger door is operating normally. If it has been wearing down also that would point towards the central locking mechanism would it not?
I'm afraid I don't follow the logic here. The electrical activation of the unlock mechanism from the handle microswitches seems to be 100% reliable, but the solenoid/cable/lock portion seems not to be.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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I was thinking along the lines of some sort of drag. My mental picture is all wacked out now, my focus is somewhere else as im starting to do the timing chain and fuel pump for the supercharger kit. I have just been keeping an eye on this since it may be relevant to my issue
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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Discussion Starter · #19 ·
I finally got around to replacing the rear locks. I had the local body shop do it as they had sat in my tool box for too long. And I don't like messing with interior panels, something always seems to break.

The new lock assemblies work great , operating with a more powerful-sounding thunk. I think the cable is just a pull cable (not push/pull as I speculated) for the mechanical interior release handle with an internal spring in the mechanism to keep it taught.

I'm pretty sure solenoids don't weaken much over 12 years, so maybe the mechanism was worn or sticky.
 

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2011 CTS4 Coupe, 2014 ELR, 2018 XT5 AWD
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I finally got around to replacing the rear locks. I had the local body shop do it as they had sat in my tool box for too long. And I don't like messing with interior panels, something always seems to break.

The new lock assemblies work great , operating with a more powerful-sounding thunk. I think the cable is just a pull cable (not push/pull as I speculated) for the mechanical interior release handle with an internal spring in the mechanism to keep it taught.

I'm pretty sure solenoids don't weaken much over 12 years, so maybe the mechanism was worn or sticky.
The door lock actuators are not solenoids they are small DC motors. The motors have a gear that meshes with a straight rack to push or pull depending on the polarity of the voltage applied to the motor. The plastic gears can wear down and cause the actuator to fail.
 
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