SL/R230: Key fob locking & unlocking
Thread Starter
Newbie
Joined: Feb 2025
Posts: 3
Likes: 0
From: Arizona
2008 SL 550
Key fob locking & unlocking
Hello!
New to the threads, so please be gentle! I purchased a used 2008 SL 550, and I cannot get the doors to lock or unlock with the remote key fob.
Spoke to the prior owner, and he said that it should work fine. I have read threads / posts etc. about this problem, but cannot figure out how to correct.
Figured I would ask for advice here, below are my tests / attempts to correct:Key Fob:
Neither door fobs go down when pressing lock button, but the alarm activates
Neither door fobs go up when pressing unlock button, but the alarm deactivates
Trunk opens as normal
Batteries in fob are brand new
Tried resetting the unlock method by holding unlock and lock (several times)
Keyless Go
New to the threads, so please be gentle! I purchased a used 2008 SL 550, and I cannot get the doors to lock or unlock with the remote key fob.
Spoke to the prior owner, and he said that it should work fine. I have read threads / posts etc. about this problem, but cannot figure out how to correct.
Figured I would ask for advice here, below are my tests / attempts to correct:Key Fob:
Neither door fobs go down when pressing lock button, but the alarm activates
Neither door fobs go up when pressing unlock button, but the alarm deactivates
Trunk opens as normal
Batteries in fob are brand new
Tried resetting the unlock method by holding unlock and lock (several times)
Keyless Go
As neither fob are down, door “unlocks” when grabbing handle
Door arms when pressing handle button, but neither fob goes down
Central Control Button:Door arms when pressing handle button, but neither fob goes down
Click unlock button (both door fobs are down):
Drivers’ door fob goes up
Passenger’s door fob does not (manually opening with door handle causes fob to go up).
Passenger’s door fob does not (manually opening with door handle causes fob to go up).
Click unlock button (both door fobs are up):
Both doors’ fobs go down
Both fobs go down when driving 9 mph as normal.
PSE PumpTrunk opens and closes
Seats work
71 fuse okay behind seat
MiscHave also pulled both door fuses in hope of reset
Both car batteries are good
MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,329
Likes: 365
From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
One thing to keep in mind is that, depending on how the locking is configured, the car may be locking/unlocking up to seven actuators (4 interior compartments, two doors, and the fuel door). Leaks anywhere in the system can drop the available pressure and prevent proper operation.
Also, the dash button function is different than the fob. Locking with the dash button just locks the doors, interior compartments stay unlocked because the car is assumed to be occupied.
Bottom line is that you almost certainly have a leak in the system. My first guess would be passenger door, but you can test each line with pressure and vacuum to properly diagnose it.
One other thing. For keyless go equipped cars, door unlock when grabbing the handle is by an electric solenoid, not pneumatics. Locking with the button on the handle is pneumatic.
Also, the dash button function is different than the fob. Locking with the dash button just locks the doors, interior compartments stay unlocked because the car is assumed to be occupied.
Bottom line is that you almost certainly have a leak in the system. My first guess would be passenger door, but you can test each line with pressure and vacuum to properly diagnose it.
One other thing. For keyless go equipped cars, door unlock when grabbing the handle is by an electric solenoid, not pneumatics. Locking with the button on the handle is pneumatic.
MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,329
Likes: 365
From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
Get one the the had pumps that will do both pressure and vacuum. Most important thing is that it holds pressure or vacuum, don't worry about a specific number. There are separate lines for each door, central locking, and the fuel door.
Thread Starter
Newbie
Joined: Feb 2025
Posts: 3
Likes: 0
From: Arizona
2008 SL 550
Okay I tested the lines from the PSE pump, results:
I would have to take the pump a part to see, but didn't know if anyone here has had this issue before?
Or do I need to buy a whole new PSE unit?
Drivers door held both pressure and vacuum.
Passenger door held neither
Passenger door held neither
Also the black plastic nub that holds the yellow line to the PSE pump (from the gray bar) was broken in side the tube.
Noticed this when I took disconnect it from the unit. It appeared to me that some one tried to glue this back on the PSE pump.
I was able to remove it, but was thinking if it was possible to reroute the line to a different nub?Noticed this when I took disconnect it from the unit. It appeared to me that some one tried to glue this back on the PSE pump.
I would have to take the pump a part to see, but didn't know if anyone here has had this issue before?
Or do I need to buy a whole new PSE unit?
MBWorld Fanatic!
Joined: Aug 2020
Posts: 1,329
Likes: 365
From: Gretna, NE
'03 SL55 Black, '03 SL500's Aegean, Mars Red, Tazanite, Alabaster, '11 S550 Flint Gray
You can try to repair it with super glue and baking soda, or tee it to the driver door and disable the passenger solenoid so it doesn't open the bad port. New pumps run around $850 from the discount dealers and used ones are around $650.
