Door Locks Cycling Without End

[DavidProehl]

I've been having issues with my power door locks. They lock and unlock on a constant loop. I have the DMCH lock module with remote. I've included a couple videos below on what is happening.

What I've tried so far to diagnose:

I've cleaned wiper switches and contacts on both doors to remove any corrosion.
I've applied pressure with my fingers to the wipers, one door at a time, to test a solid connection is being made.
I've run a diagnostic on the lock module by pressing the button on the module, which displays a lower red and upper green concurrently flashing light. I believe this means it thinks the passenger unlock failed.


I'm wondering if there is an issue with the lock module itself. I'm surprised that the default behavior would be to lock and unlock without ceasing, ultimately this would drain the battery. I've only let it go about a dozen cycles before disconnecting the power, so perhaps it would stop eventually, but I'm skeptical.

The lock module will stop misbehaving if both doors are open with the wiper switches not making contact with either lock or unlock. If either one of the doors is in the lock or unlock position, it goes into the cycle. I'm starting to think maybe there is an issue with the lock module itself?

Any thoughts on next steps to try? I'm wondering maybe I need to test continuity with a multimeter between the wipers and the connector that mates with the lock module. Not sure what else to look at.

I appreciate the help on this!


https://www.youtube.com/watch?v=c2ta-i4oNPU

[David T]

Make sure both doors (and both latches on each door) are in 2nd locking position. If one is not then it would cause the module to unlock the doors. Disconnect the DLM and check each door and each latch. Slowly close each door and listen for 2 clicks from each latch. When properly adjusted you should not be able to lock the door manually if both latches are not in 2nd locking position.

[Bitsyncmaster]

The wiring in the stock harness puts the door switches in parallel so if one switch fails to follow the other then the electronics will see both unlocked and locked and has to decide what to do with that. So my guess is the software did not consider that possibility.

You may have a broken or shorted wire in the harness or the adjustment of the switches is causing that problem. What you could do is pull the connector from one door switch (inside the door) and using an ohm meter at the door lock ECU connector verify the lock and unlock signals follow when you manually lock and unlock the other door. If that door works then do the same to the other door.

[CFI]

I’ve never been a fan of the central door lock system. In stock form it’s probably one of the worst offenders as fas as battery drain is concerned, and even if it’s functioning correctly (which it probably won’t do for very long) it’s gimmicky at best. Central door locking for a tiny, two door car? Really?

I’d unplug it and call it a day. The hassles it creates aren’t worth the service it’s supposed to provide.

[DavidProehl]

Make sure both doors (and both latches on each door) are in 2nd locking position.
The doors seem to latch properly after re-checking. Without the DLM connected locks and doors work as expected as well.


You may have a broken or shorted wire in the harness or the adjustment of the switches is causing that problem. What you could do is pull the connector from one door switch (inside the door) and using an ohm meter at the door lock ECU connector verify the lock and unlock signals follow when you manually lock and unlock the other door. If that door works then do the same to the other door.
Apart from a faulty DLM a short is probably the only other situation that makes sense. So essentially you are saying I should confirm the lock/unlock signal makes it to the DLM? I'll give this a try tonight. If there is a short, then it is possible both doors could work with the other disconnected but not together right? I'll test the signals first and theorize more later.


I’ve never been a fan of the central door lock system. In stock form it’s probably one of the worst offenders as fas as battery drain is concerned, and even if it’s functioning correctly (which it probably won’t do for very long) it’s gimmicky at best. Central door locking for a tiny, two door car? Really?

I’d unplug it and call it a day. The hassles it creates aren’t worth the service it’s supposed to provide.
I can't disagree with you on the trouble this system causes. It's never been 100% for me. Even so, I still really like my remote locks despite the headaches.

[David T]

The electronics won't correct a mechanical problem, if the doors are not set up and adjusted perfectly the DLM won't work. Make sure all the latches get to 2nd locking position.

[Elvis]

I’ve never been a fan of the central door lock system. In stock form it’s probably one of the worst offenders as fas as battery drain is concerned, and even if it’s functioning correctly (which it probably won’t do for very long) it’s gimmicky at best. Central door locking for a tiny, two door car? Really?

I’d unplug it and call it a day. The hassles it creates aren’t worth the service it’s supposed to provide.


I tell people to update and use it.

[DavidProehl]

Verified latches, they are good.

I've now also disconnected the wipers and set both to unlock and both to lock using alligator clips on the connectors. No dice. I've also tried:


With only 1 door connected, both still cycle.
With only 1 door connected, I can short the other lock or unlock with alligator clips and they both cycle.
I tested continuity between the door unlock and lock wires and the harness in the relay/fuse compartment and it is good for all wires.
I tested if I could get continuity between lock wires in one door and unlock on the other door, I could not (no short between them)
I replaced my DMCH DLM with the factory DLM...AND IT WORKS!

So I imagine it is now conclusive that my DMCH DLM has a fault in it correct? I wonder what the warranty period is on these. Crazy that my 41 year old DLM works fine and my new fangled one won't.

OEM Door Lock module with everything working as it should, although without any remote functionality:

https://www.youtube.com/watch?v=CWplRbqUV2I

[DavidProehl]

More fun video of my issue in action with my jumper wires in place:

https://www.youtube.com/watch?v=jAN7zYennzg

[Bitsyncmaster]

If there are any remote wires feeding the ECU, try disconnecting those.

[DavidProehl]

If there are any remote wires feeding the ECU, try disconnecting those.

Genius! That did it! I disconnected the remote box from the DLM, and then it worked properly! I then reconnected the remote and now it works with the remote as well!

Thanks so much Dave!

[Ron]

If there are any remote wires feeding the ECU, try disconnecting those.
+1

A side thought-
I'm thinking, in the last vid, if the jumper wires were removed, it would act the same -- Disconnecting the switches ("sensors") and grounding their harness connectors does nothing but remove the ground source used as input to the module.

Glad it's working in any case!

[DavidProehl]

Jumping back on this thread as the locks started cycling again. If I disconnect the wireless receiver from the lock ECU, then power locks function normally (like stock) on both sides but without remote functionality obviously.

Does this sound like the receiver plugged into the ECU might be defective? I'm wondering if is starting to fail entirely which explains why it worked after resetting previously, but now it won't. I wouldn't expect them to wear out over time, but I imagine it could happen.

[MrChocky]

Jumping back on this thread as the locks started cycling again. If I disconnect the wireless receiver from the lock ECU, then power locks function normally (like stock) on both sides but without remote functionality obviously.

Does this sound like the receiver plugged into the ECU might be defective? I'm wondering if is starting to fail entirely which explains why it worked after resetting previously, but now it won't. I wouldn't expect them to wear out over time, but I imagine it could happen.

The ECUs can fail over time - old electronics, etc. I do have some NOS units, but there's also some modern versions kicking around. But it's always worth cleaning connectors.

[David T]

The ECUs can fail over time - old electronics, etc. I do have some NOS units, but there's also some modern versions kicking around. But it's always worth cleaning connectors.

It's worth checking the battery voltage, electronics can act weird of they do not get what they want. Low voltage an cause weird things to happen. After a long period of inactivity (which many Deloreans get) the battery can get low.

[DavidProehl]

The ECUs can fail over time - old electronics, etc. I do have some NOS units, but there's also some modern versions kicking around. But it's always worth cleaning connectors.

The ECU/DLM seems to be functional without the receiver attached. I have a DMCH Door Lock Module I bought and installed in 2012 that it is connected to. I suppose that the issue could be in either of them.


It's worth checking the battery voltage, electronics can act weird of they do not get what they want. Low voltage an cause weird things to happen. After a long period of inactivity (which many Deloreans get) the battery can get low.

Good call out. The voltage seems fine, I keep it on a battery tender, but I can certainly verify the voltage is a strong 12v.

[DavidProehl]

Hopefully my final follow up on this. Last night I found the remote receiver was attached to a bad ground. Couldn't find it with the multimeter but bought a 12v single wire light for $8 that found it right away.

Painful lesson about the proper way to verify ground connections. I've heard "check your grounds" a lot on this forum, should have known better.

The bad ground was caused by a tap connector I received with my door popper kit. After all this trouble I can assure you I won't be using tap connectors any longer! I knew better when I installed it, but did it anyway.