SLK/R170: Locking and alarm issue
Thread Starter
Junior Member
Joined: Dec 2001
Posts: 36
Likes: 0
From: The Woodlands, TX
slk 230
Locking and alarm issue
When I lock the car all the locks function normally, then the alarm sounds. Unlocking the car stops the alarm, then about 20 seconds later the car locks itself and the alarm sounds again. The only way to stop this cycle is to open a door when the car is unlocked.
I checked the PSE, it doesn't show any sign of corrosion. The car has been garaged since new.
I replaced the K40 relay last year when the car would turn over but, not start.
I checked the PSE, it doesn't show any sign of corrosion. The car has been garaged since new.
I replaced the K40 relay last year when the car would turn over but, not start.
Newbie
Joined: Apr 2025
Posts: 2
Likes: 0
slk320
Old thread and hopefully solved, but for anyone else, I had the same issue and it's supposedly somewhat common.
Likely cause: plugged drains under the trunk lid.
A clogged drain allows water into the trunk area which flows down into the spare tire area.
This matters because adjacent to the spare behind the foam piece in a box made of soft foam (I don't know if it's standard but mine looked like it was wrapped in duct tape or some silver poly fabric) is the a part someone else called "the PSE" whatever that stands for.
This part controls the locking mechanism of the car. Water enters this and corrodes the electrical connectors. The black connector on my unit was caked in green corrosion.
Thankfully I was able to clean them with alcohol, get some grease on them and everything is normal now.
However, if the problem isn't fixed by a simple cleaning, leaving the unit unplugged will stop the alarm, definitely at the cost of you key fob functioning, and I'm not certain, but I'd image the top won't function either.
Likely cause: plugged drains under the trunk lid.
A clogged drain allows water into the trunk area which flows down into the spare tire area.
This matters because adjacent to the spare behind the foam piece in a box made of soft foam (I don't know if it's standard but mine looked like it was wrapped in duct tape or some silver poly fabric) is the a part someone else called "the PSE" whatever that stands for.
This part controls the locking mechanism of the car. Water enters this and corrodes the electrical connectors. The black connector on my unit was caked in green corrosion.
Thankfully I was able to clean them with alcohol, get some grease on them and everything is normal now.
However, if the problem isn't fixed by a simple cleaning, leaving the unit unplugged will stop the alarm, definitely at the cost of you key fob functioning, and I'm not certain, but I'd image the top won't function either.
Thread Starter
Junior Member
Joined: Dec 2001
Posts: 36
Likes: 0
From: The Woodlands, TX
slk 230
Previous research had said to check the PSE for water damage. Others had reported that cleaning the connections or replacing the unit solved the issue. My car has always been garaged so I didn't think that was the problem though I looked at it anyway. I didn't see any indication of water leakage in the trunk or on the PSE unit. I didn't want to spend the money to replace it without knowing if that was the problem.
I'm glad cleaning yours fixed the problem.
I'm glad cleaning yours fixed the problem.
