Having problems with door locks on 08 Cadillac CTS. Driver side door especially and will not lock or unlock with key. Others loc

I am experiencing problems with the door locks on this vehicle. The key does not lock or unlock the vehicle and power locks did not work on any doors. The module on the drivers side was replaced and all doors except drivers door locked and unlocked with main control. However, after a while all doors including driver side were inop. Problem with door lock appears to be intermittent except for driver side which is consistently inop.

My car has 150000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
This is often related to a malfunctioning door lock actuator, a blown fuse or a faulty power door lock switch. When you use the door lock switch in the car it sends a signal to a relay which then activates an actuator inside the door. The actuator is the final step in the process in that it is a small motor with a set of gears that actually locks and unlocks the latch mechanism inside the door allowing the door to open. When this motor is bad, the latch mechanism will fail to operate and cause the door not to unlock as it is designed to. In the case of a bad door lock relay, the power, normally needed to send the signal from the switch when you activate it to the actuator motor is not there. This means the relay is not allowing the circuit to be completed and the actuator motor is not activated. Any of the above may cause your power door lock switches not to work properly and should be diagnosed by a qualified mechanic. I would suggest having a professional from YourMechanic come to your location to take a look at the door locks in your vehicle.

How to Identify and Fix Common car Problems ?

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The most common cause of a door not unlocking with your remote key is a broken door lock actuator. To keep from needlessly removing and installing a new door lock actuator, there are a few ways to diagnose a bad door lock actuator that we`ll discuss further.
A problem with one lock is probably due to the lock actuator or another malfunction inside the mechanism of the door itself. But if none of the power locks work, check the fuse box in your vehicle. A blown fuse can cause the power locks to stop working.
Lack of lubrication. Moving parts always experience friction, so a possible cause of the driver-side door locks not working is a poorly lubricated door latch. For this issue, check if the latch mechanism on the door has any corrosion that could be hindering the lock.
If the battery dies, the fob chip loses power and will not open or close your car doors. To avoid such frustrations, ensure you are stocked with spare batteries or a backup key. Another major issue in the key fob is misaligned buttons and broken contacts. You can open the key fob to check if it has any issues.
One common reason the car door lock is stuck in the locked position is due to broken connections within the door panel or lock assembly. These include a broken link from either the handle, lock cylinder, or interior locking post/switch to the car door latch.
In most cases, when a single door will not open, it`s due to a broken latch – which will require replacement. As long as you can get into the vehicle, you should be able to climb into the driver`s seat and drive home safely until you have time to contact a mechanic to find the issue and make the right repairs.
One of the first symptoms of a possible problem with the door lock relay are door locks that function intermittently. If the door lock relay has any internal or wiring issues, it can cause the door locks to function intermittently. The door locks may function correctly one moment, and in the next will cease to operate.
The most common culprit behind an electric key fob`s failure is, as you might guess, the battery. This is a relatively easy issue to fix, although you may need to get a ride to get to buy a replacement fob battery.
Chances are, the switch is simply not allowing enough voltage through to actually unlock the doors. Again, check the unlock button for a poor wiring connection, a dirty switch, or any other sort of obvious damage. If nothing seems to be wrong, it is a good time to do electrical testing while you have access.
Door lock problems are often caused by a malfunctioning lock mechanism or latch assembly, but there are several common reasons why locks stop working: The lock is dry or dirty. It doesn`t fit in the door properly. The latch and strike plate don`t align.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Having problems with door locks on 08 Cadillac CTS. Driver side door especially and will not lock or unlock with key. Others loc
ANSWER : This is often related to a malfunctioning door lock actuator, a blown fuse or a faulty power door lock switch. When you use the door lock switch in the car it sends a signal to a relay which then activates an actuator inside the door. The actuator is the final step in the process in that it is a small motor with a set of gears that actually locks and unlocks the latch mechanism inside the door allowing the door to open. When this motor is bad, the latch mechanism will fail to operate and cause the door not to unlock as it is designed to. In the case of a bad door lock relay, the power, normally needed to send the signal from the switch when you activate it to the actuator motor is not there. This means the relay is not allowing the circuit to be completed and the actuator motor is not activated. Any of the above may cause your power door lock switches not to work properly and should be diagnosed by a qualified mechanic. I would suggest having a professional from YourMechanic come to your location to take a look at the door locks in your vehicle.

all doors lock only by inserting key in passenger side door and locking
ANSWER : Your central locking system may have been designed with a control module in the circuit. This is a small computer that is responsible for controlling the different functions of a particular system. It is possible that the module for your central locking system may have shorted out internally preventing particular functions from working properly. I would recommend having a certified technician test your central locking module to determine if all of its functions are working properly.

Driver side door lock button not working, and passenger side sliding door makes a buzzing noise
ANSWER : Hi there. These door issues are common on this vehicle. Most of the time the main issue is the master door lock switch on the driver door. It sounds like you already replaced that. As for the sliding door problem, most of the time, this is a failure within the door module or it can be a connection issue.

I typically take the door apart and check the connections on the module and inside of the door just to make sure that there is nothing apparent in there. If the connections and the wiring are fine, then I use a scan tool to check the module to see what the inputs and outputs are doing. If you need to have this looked at, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your door problem and recommend a repair.

Driver and Passenger doors won’t lock, but I hear them click and see the locks twitch.
ANSWER : If the same problem is happening even when you use the inside door lock switch then the most likely cause of the locks not moving is going to be weak actuators. You should replace the drivers lock actuator first since it is used the most and you will see it fixes the problem. Then you can replace the other doors as needed.

Door lock problems
ANSWER : Hi there. There is a resistor for the door locks that keep a voltage on the driver door lock cylinder to activate the secondary door locks electronically. If the resistor is leaking (losing power) it tends to cause the door locks to not work. You can try unlocking the driver door, then open the driver door and use the key to unlock the other doors. This will supply power directly to the driver door lock cylinder and bypass the resistor. If the other doors unlock, then the resistor needs replaced. If the doors do not unlock with the key and the driver door open, then the door lock cylinder on the driver door will need replaced. If you need further assistance with your doors not unlocking when turning the key twice, then seek out a professional, such as one from Your Mechanic, to help you.

Passenger side door not unlocking manually with key. Key won’t insert into the door. Trunk lock works fine.
ANSWER : Hi there. The door lock cylinder has either an object in side it causing the key to not fit or the pins inside the cylinder has fallen into the key hole. I recommend replacing the door lock cylinder. If you need further assistance with your key not working in the door lock cylinder, then seek out a professional, such as one from Your Mechanic, to help you.

Doors wont lock or unlock with fob or switch?
ANSWER : Hello. Further testing should be done to help solve your problem. Being that the door unlock reprogramming procedure has already been done and the fuses have been checked there’s not much left it could be. When you hit the unlock button you should hear a little noise in each of the doors. If you hear the noise that means that the motor inside of the door actuator is working therefore it is likely the actuator itself as the problem. Though if you do not hear any noise that means it is likely the motor inside of the actuator. The actuator motors are very common failure on Lexus. The Lexus Community is almost an uproar because the a L in Lexus should also stand for luxury but there have been widespread simple problems reported such as this. A technician such as those we have here at yourmechanic will be able to diagnose your door lock issue for you firsthand. But if you consider following the test I suggested that should help you narrow down to a solution as well.

It may also be a beneficial to take a door panel off and probe a multi meter to the door actuator connectors to ensure they are receiving the proper power and ground when the buttons are pressed. If they are that only leaves two things that can be at fault. The door actuator or the motor inside of the door actuator.

Door unlocked alarm, no power window or door lock on driver door only, interior light comes on with L turn signa
ANSWER : Hi there. In general, wiring harnesses are sold by the manufacturer as a whole harness; not individual wires. It is much easier, cost-efficient and safer to replace the entire harness if it’s determined that it is faulty and the source of your alarm / door issue. It would be best to have one of our mobile mechanics come to your location and complete an electrical problems inspection though, as it’s possible that this issue is related to an error code trapped in the ECU. If this is the case, simply clearing the code will resolve the problem. If the issue is determined to be the wiring harness or an exposed wire, they can recommend and most likely complete the repairs as well.