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Discussion Starter · #1 ·
Good day to you all - my 99 S320 without soft close has an unusual problem where the trunk opener at lid, door or remote fails to work. I have to use the blade key. If I disconnect the battery for half hour or so the system works fine. However, on start up the engine runs rough and won't accelerate. It takes a while for the engine return to normal operation. The trunk lock will work fine for a week or two or three the stop, needing a reset. Any suggestions out there?


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2005 S600 / 2005 SL600
1,095 Posts
First, STOP disconnecting the battery. The car hates it, you’ll need to reset steering angle sensor, sunroof, and windows every time you do, and yeah, you’re losing some adaptations in the ECM.

If you have to use the blade key, then you likely have a vacuum leak between the PSE pump and the actuator. Usually, it’s the actuator.

The PSE pump measures how long it has to run to accomplish a function (lock, or unlock, open trunk, whatever). If that time is exceeded, then the PSE pump shuts down that branch to protect itself from overheating. That’s a good thing, a new pump is about $600 and has to be programmed to work in your specific chassis with your options.

So, that’s what is going on here. The pump sees the leak, shuts down, and you have to use the key.

Time to chase down the leak. Google is your friend. Lots of videos on how this actuator fails and how to diagnose, and then repair or replace it.
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