Some door lock advice please

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wtgriz

10 Year
Joined
Jul 10, 2012
Threads
2
Messages
19
Location
Florissant, Colorado
I have a 2000 LC with an intermittent door lock issue I'd appreciate some opinions on troubleshooting. Occasionally when using the remote, or key to lock/unlock all of the doors from the driver, passenger, or tail gate, none of the 5 locks will fully lock/unlock. All of them move or make a sound to some extent but it's like there aren't getting enough power. This is a fairly random occurrence, although seems to be increasing in frequency, and much of the time all of the locks work fine with both the key and remote. Another potentially related issue I discovered while trying to follow some instructions for programming a new key is that when using the interior lock/unlock buttons cycling the locks more than 2 or 3 times causes the same issue. They just get weaker and weaker until they just kind of twitch.

I have read the posts on actuator motor replacement but the fact that all of the locks behave the same way makes me think that there may be another cause.

Again, any opinions or trouble shooting advice would be welcome. I'm not an electrician or mechanic but am reasonably handy and am good at following instructions.
 
Thanks for the reply!

I have only noticed all 5 locks acting up at the same time. Of course when using the key on the driver's door, that door unlocks mechanically. However, after that, even using the interior button seems to have the same weak affect on the remaining locks. Sometimes starting the engine helps, sometimes just waiting a few minutes helps. Without knowing all of the locking components or their interactions, if I had to guess, it seems that there is some master control and for whatever reason, occasionally it does not send out a strong enough pulse to operate all of the locks. Also, cycling the locks more than a couple of times even when they are all working correctly, seems to have a draining effect on the system.

I don't thinks it a battery or general power issue as all other power systems seem fine, windows, lights, etc.
 
Regarding the battery not being the an issue, try this:
start the engine and get the rev's up about half way on the tac. The reason is that at idle you generally don't have enough juice going through your alternator to charge the battery. So if your battery is in anyway low, or you don't have clean tight connections on your battery, this might so it.
You might be surprised that what you find.
... but again, maybe not...
 
I guess what I'm really asking is - does anyone knows if there is some central, master control module whose function it is to relay a lock/unlock signal to all of the doors? If so, what is it called / where is it / where is the best place to look for a replacement / and do my symptoms sound like a failure of this module? Or, does my problem sound more like a failure of the individual motors in the door lock actuators? I already have the new motors, just trying to avoid tearing into all 5 doors if replacing these motors isn't the most likely cause of the problem.
 
Sound's a little like it is a per door issue and not the entire system. That's just my 2 cents.
I don't see why a central module would have some locks be snappy and others sluggish at the same time, unless there is some connection issues in your wiring?:hhmm:
 
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As much as I'd love to sell you a set It doesn't sound like an actuator issue to me. I have never read or heard about it occurring on all locks simultaneously and then not at all, it's always a single door or a couple doors and they always seem to act up independently of each other. Sounds like a relay or switch to me.
 
wtgriz said:
I guess what I'm really asking is - does anyone knows if there is some central, master control module whose function it is to relay a lock/unlock signal to all of the doors? If so, what is it called / where is it / where is the best place to look for a replacement / and do my symptoms sound like a failure of this module? Or, does my problem sound more like a failure of the individual motors in the door lock actuators? I already have the new motors, just trying to avoid tearing into all 5 doors if replacing these motors isn't the most likely cause of the problem.
Click to expand...

Yes.

There are two major components in this equation that can be an issue.

1. The Master switch in the drivers door

2. The center ECU (lives above the radio

I suggest checking the wire loom from the drivers door to the dash - looking for broken or crimped wires. Failing that then the above could be an issue.

Edit: there is a wireless door lock ECU as well. It's located on the drivers side behind the knee panel.
 
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Thanks for the replies - I'll check the wiring and hope that I get lucky and find something. That would certainly be the easiest/cheapest fix. I have already purchased new actuator motors but the more I thought about it, it just doesn't make sense that all of the locks either work or not at the same time, and the issue where they all stop working if locked/unlocked more than a couple of times quickly also has me puzzled. If I don't find any broken/crimped wires I'm not sure how to troubleshoot further. May have to pay a dealer to diagnose and then try and find parts and fix myself. Hope it doesn't come to that though.
 
Any update on this? I'm experiencing the same thing. Most of the time it's all the locks on my 99 when it's hot out. Occassionally, it is the passenger or cargo door by itself. Sounds to me that the passenger and cargo are most likely actuator candidates. But I'd like to know what you found when the whole system stops working for a period.
 
mikgrail3 said:
Any update on this? I'm experiencing the same thing. Most of the time it's all the locks on my 99 when it's hot out. Occassionally, it is the passenger or cargo door by itself. Sounds to me that the passenger and cargo are most likely actuator candidates. But I'd like to know what you found when the whole system stops working for a period.
Click to expand...

This happens to me. I'm thinking I need five actuators.....I'm just too cheap to give jonharis $25.......
 
wtgriz, any updates on your lock issue? I can't program a new remote with the locks acting this way...frustrating. :mad:
 
Sorry for the delay in updating - have been traveling and haven't checked in for awhile.

I do have a lead on the cause but do not have it fixed as yet. I was told by a mechanic friend of mine, who will not touch electrical problems on any vehicles but his own, that it sounded like a problem caused by a faulty relay. This guy deals with this type of issue daily at his job testing engines at a small manufacturing plant and said everything that I described, the intermittent nature of the problem, the slowing down of the lock when cycled 3 or 4 times in a row, and the fact that all of the locks act the same in unison, screamed a faulty relay. I'm talking about the small, brown or black plug-in type of relay which I did not know is actually a mechanical switch that frequently wear out, especially on circuits of high use like door locks. I checked online and sure enough, several sites sell a 5 prong "door lock relay" for the 100 series LC for $30 - $50. I picked one up at NAPA just before heading out of town.

Now the problem is that I have been unable to find where the relay is on the vehicle. I just started a new thread yesterday "Location of power door lock relay?" asking if anyone had replaced one and knew where I could find it. I list several places that I've looked in this thread.

On another note, like I posted earlier, I bought new actuator motors for all of the doors and even replaced the one in the passenger front door. It's a JOB and I'm more convinced than ever that these motors are not my problem. I managed the get the new motor in and the door back together and it works just like it did with the old motor in it.

So, when I find out where they’ve hidden the relay and replace it, I’ll let you know if that is the fix we are all hoping for. Besides the general aggravation of it not working like it’s supposed too, I also have a new key that I’m wanting to program and the locks quit working before I can get the correct number of cycles in.
 
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Report back on how that relay works out. I'd much rather replace that than 5 window motors. Keeping my fingers crossed.
 
I am having a similar problem, just started yesterday. When I click my keyless and the drivers side door button, my lock switches move but the door does not actually lock. It seems to be an ittermitent problem. Any idea what this might be? I had a new audio system installed this week, could it have been caused by this. I think yes.
 
Okay, here is the latest in this saga – Thanks to input from re-guderian and RobRed, I located and removed the junction box and replaced all three door lock relays (all the same part). Worst job that I’ve ever undertaken by far. At 6’-2” & 230, I’m not exactly built for working in this location so after spending about 3 hours on the removal, twisted up like a pretzel and thinking I might have to go to the hospital, I paid a mechanic buddy to come over and finish the job which only took him an hour - show-off.

The relays were not the problem. Sorry mikgrail3, I was hoping that this was it too, especially since I had just spent $75 on replacing what turned out to be perfectly good parts. All of the locks quit working after 2 or 3 cycles – except one. Now for some good news, even though it involves admitting something that makes me look like an idiot.

I started on this adventure 2 months ago thinking that I had the well documented actuator problem that so many have written about. I even purchased new actuators and replaced the one in the passenger front door. This was a big job in which I managed to break the clip off of a $45 door lock clip wiring harness while in the middle of, so I had to wait a week for a replacement harness before I had it totally finished and back together. It was about 15 minutes before the wife and kids were to take off on a 4,000 mile road trip in the truck that finished the actuator replacement. I made sure that the new actuator worked the lock, but apparently I was so relieved that I had managed to get everything back together in time for their trip that I guess I didn’t cycle the locks several times to see if this one acted differently. In the mean time, while the truck was gone for 2 weeks, I kept reading posts and convinced myself that it was very unlikely that my problem was with the actuators because the locks in my vehicle stopped working on all of the doors at the same time after cycling the locks 2 or 3 times. How could 5 independent motors all quit working at the same time? There had to be a central cause, right? Even my mechanic agreed and suggested a relay as the likely root cause.

So, imagine how dumb I felt sitting there testing the locks after replacing the relays when all of the locks quit working after 2 or 3 cycles, just like always, except the front passenger door that I had replaced the actuator in 3 weeks ago. I must have cycled the locks 10 or 15 times and this one door worked perfectly every time. So, while it still doesn’t make any sense to me that all of the actuators started failing at the same time, I’m now going to replace the actuator in another door and then re-test. If that door also works after several cycles then I’ll finish the rest of them. I’m hopeful that now that I’ve done one that I can do the rest without breaking any other parts. I’ll post back after the 2nd door is finished. Enjoy your chuckle at my expense and thanks again for everyone’s input.
 
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