Rick's Free Auto Repair Advice

Power door locks not working — How to diagnose and fix

Learn how to diagnose and fix power door locks that don’t work

Power door locks are pretty simple devices. Most have just This image shows a typical door lock actuatortwo wires, and they lock and unlock when power and ground polarity are reversed. If your power door locks don’t work, the problem can be caused by a bad actuator, a bad door lock switch, an issue with the wiring harness, or a module issue.

Symptom tips to diagnose a power door lock problem

Is the problem limited to just one door?
If so, that means the fuse is good, and you can eliminate it as the problem. That leaves the wiring or the actuator as the problem.

Does the problem happen only when you use the door switches?

If all the door locks work when you use the remote key fob, but one or more don’t work with the door switch, that eliminates the actuators as the problem and narrows it down to a switch or wiring issue.

The easiest way to start your diagnosis is by testing for power and ground at the actuator

To perform these following tests, you’ll need a image of a door lock actuator connectorcomputer-safe test light or digital multimeter. You’ll also have to remove the door lock switch and even the door panel itself. Refer to a shop manual for directions on how to remove the door panel.

1) Unplug the door lock actuator electrical connector.
2) Connect your meter leads to the electrical connector and operate the door locks; lock and then unlock. You should see the voltage polarity toggle. If you see that, it proves the switch and wiring to the actuator are good, and the door lock actuator bad. If you don’t see the voltage toggle, work backward to the switch to isolate the problem.

If the vehicle uses a door module or BCM to operate the locks

You’ll need a scan tool with live data and a wiring diagram. I’ll assume that you’ve already tested for toggling power and ground at the actuator connector. If not, do that now.

1) Connect the scan tool and navigate to the live data for the power door locks.
2) Operate each door lock switch and monitor the scan tool to see if the module or BCM is receiving the lock/unlock request. If so, that confirms the door lock switch and wiring to the module are good. If the module isn’t getting the door lock request, trace continuity between the module and the switch. If that’s good, the problem is in the door module or the BCM.
3) If your scan tool shows the lock/unlock request but there’s no power at the actuator, use a wiring diagram to locate the power and ground terminals to the actuator at the module or BCM. Backprobe those terminals to check for toggling power and ground. If you see that, the problem is in the wiring harness from the module to the actuator. If not, the module is bad.

How to replace a failed door lock actuator

The actual procedure depends on the year, make, and model of your vehicle. Late-model vehicles have the actuator built into the door latch assembly, forcing you to replace the entire latch. Older vehicles usually have a separate actuator. The actuator can be located away from the latch and operate the latch via linkage, or it can be attached to the latch by plastic clips or screws. To see and operate the latches/screws, you’ll need a mirror and curved picks.

Which lock actuator should you buy?

Lock actuators are failing more often, and that increased failure rate has created a business opportunity for aftermarket suppliers to sell replacements at a fraction of the dealer’s price. Many of these units come with a lifetime warranty despite the fact that they’re often poor-quality units. If you don’t like replacing the factory door lock actuator, I can assure you that you won’t like it the second or third time around when the aftermarket actuator fails. Before buying an aftermarket door lock actuator, check out the reviews. Also, check online OEM prices from sites like parts.com.

Normal versus abnormal door lock actuator sounds

A solenoid-style actuator makes a single clunk sound when locking and unlocking. But a DC-powered motor makes a much different sound because these units have gears. In normal operation, you’ll hear a short whirring sound. However, as these units fail, the noise gets door lock actuatorlouder, indicating they’re worn and about to fail. Any grinding sound during the lock/unlock operation is also an indication that the actuator is failing.

Door lock actuators can also behave erratically

Some lock motor-style actuators are designed with a rubber bumper stop component. The bumper stops the lever at the end of travel and cushions the movement to prevent gear breakage. The door lock controllers in these vehicles look for the current spike once the lever reaches the end of its travel. If the rubber bumper breaks or fails in any way, the controller won’t be able Honda door lock actuatorto tell when the lock has finished its travel. In some cases, the controller interprets the lack of current spike as a sign of a problem, causing the door lock actuator to lock and then immediately unlock. The actuator/controller can do this consistently or erratically. If you notice the door locks behaving erratically, don’t automatically assume you’ve got a bad controller. It’s most likely a failing door lock actuator. Unfortunately, it can be caused by any of the vehicle’s actuators. Worse yet, since all door lock actuators operate at the same time, they also wear equally. So you can replace the suspect actuator only when you discover that the others require replacement as well.

Erratic operation can also be caused by a frayed wiring harness in the door hinge area or inside the actuator itself.

Another symptom of a potential problem with the power door lock actuators are door locks that behave erratically. If the actuators have any sort of internal or wiring issue, it may cause them to rapidly lock and unlock unexpectedly, or cause them to function intermittently.

©, 2016 Rick Muscoplat


Posted on by Rick Muscoplat


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