Per ardua ad cineris.
Join Date: Apr 2013
Location: Somerset UK
Vehicle: SLK230 '99 R170
Other Toys: Clio Williams
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Once the normal communication have failed...
My knowledge is based on the basis that I have never had a PSE in my car.
So, I realised that the PSE is instructed to open/close by a message over the CAN bus, from the CCM/SKF.
The CCM gets a discrete signal from the radio module, and can therefore use this signal to drive alternative mechanisms.
The CCM also gets the signals from the internal central locking switch, so could have these patched in to the same alternative mechanism.
I have used these signals to drive isolation relays that then power the motor relay in my replacement PSE, which can then drive the locks. Replacement PSE needed a couple of modifications; more later.
I have run the PSE directly off these wires for a while (couple of weeks) and they worked OK. I then connected to both the lock and unlock signals, and the lock worked well, but the unlock did not work. (Lock also seemed not to lock the boot)
Realised that the unlock signal was because of a broken wire, and eventually (today) replaced that wire and got the unlock to start working.
So now both remote lock and unlock work; the bug is that the signals were expected to run whilst the fob button is pressed, but it only runs for about 0.5 seconds, which is barely enough to get the pump running, let alone compress the system (including the boot lock). So currently I have to multi-tap to get all the locks driven.
So, ongoing, but as yet incomplete, but going in the right direction.
But this is for a system that is thoroughly broken, so abandoning the possibility of repair to the PSE is not an issue for me.