I have two questions I need help with:

1). I've plowed through all the CLM posts I can find, but I don't see any guidance on this problem.
In short, the fob won't lock or unlock the car, but flashes the lights and sets the alarm. But it's NOT the pump - I swapped pumps with a donor car and the problem did not migrate to the donor. The system in the donor car works on either pump. Neither pump will operate in the new car. I am very sure that the pump isn't running at all, total silence.
The wiring and connectors look very clean, but I don't know how to confirm if they are operational.
2). I was thinking it may be the Relay Module or BCM. I could try swapping one or both of those, but not sure if they are compatible. Donor is a 2004 Limited Coupe. New car is a 2005 SRT6 Coupe. Would it make sense to try swapping in those boxes? If so, would it be safe to do that?

 

sounds like a faulty siren causing the electrical gremlin

 

It could be a BCM problem. As far as I know, it will not damage a known good BCM to be installed in your car to help diagnose the problem. My BCM kinda died recently and one of the symptoms was that it would not physically lock/unlock the doors. The BCM instructs the Security Module in the trunk to lock or unlock the doors.

 

Let's keep our fingers crossed. My one concern is that the BCM from the 2004 might be looking for the rear wing position and control switch, which are not in the 2005 SRT6…

 

The BCM must match the car, the SRT one will not work in an NA, or so Ihave heard.
CLM? What is that?
Have you played around with the fob? Like change the case?

 

Thanks for your input. I had planned to test drive the SRT (in the event the module swap worked) to see if it would cause limitations. Anyway, swapping the Relay Module and BCM did not help and everything is back as it was.
I did double check for correct battery installation in the fob. If a new case might help I'll try it. The supplied OEM fob is in pretty good shape though.
(CLM - I guess I had modules on the brain when I posted. I meant CLS, System not Module.)

 

Hi Rob, I have to say I thought you making a joke, but after searching about the alarm module, I see that you were not. Thanks, I'll try the siren.
BTW, my "new" car has your cold intake. I'll check out your website and see what's up with that.

 

Yeah, it seems the batteries rotting out inside the siren causes some kind of feedback into the electronics systems and cause undesirable results. Many have just unplugged the siren under the cowl (make sure you cover/wrap the connector). If this solves the issues, good. If it caused other problems (unless it wasn't the issue), you'll be back to square one. Good luck!


.

 

Well, back to square one it is. Disconnecting the siren didn't help, nor did switching in a known good siren.

Had an idea - is it possible to get the lock/unlock switch (on the console) to work without the ignition switch on?
If so, I could wire in an external switch in parallel to the console switch. Of course, I would only do the "lock" side of the switch and use the door key for unlocking.

 

I have no idea, as I don't usually hack into the wiring of something I'm currently trying to fix. Sorry.


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I have a reasonable, though not ideal, solution for getting the rear hatch locked. The lock system rocker switch (on the console) behaves as follows on my car:
- Only locks when the ignition switch is in Accessory or Run position. (I believe it's supposed to work in any ignition switch state).
- Only locks when driver's door is closed.
- When system is locked by the console rocker switch, both doors and rear hatch lock. (I believe the fuel hatch is supposed to lock, but mine does not).
- Opening the driver's door activates unlocking of everything.
- The result is that I can only lock the doors manually with the passenger door lock plunger and driver door key lock. The car cannot be left with the rear hatch locked.
I figured that the rear hatch should stay locked if the system "thinks" the driver's door is closed. Some fiddling around revealed that the unlocking is dependent on the door position switch, conveniently located in the door jamb just above the latch striker. It's easy to access by removing the door seal and peeling back the sidewall carpet, then pushing the switch out from the inside. Just pulling the connector works, but I didn't want a loose connector, so I removed the spring from inside the switch so the plunger stays retracted.
Now I can stop, hit the console switch, *then* turn off the ignition, and everything is locked. The driver's door handle will mechanically unlock the door, which I can re-lock from the outside with the key. I doubt I'll be able to lock the fuel door without restoring normal operation to the whole system, which is doubtful.
Not great, but at least the car can be secured now.

 

luxige You have a bad #9 fuse in the under hood box. It is 10 amp. Get a good fuse and you should be OK. DO NOT mess with the door switch wires! Why create another problem. Fix the one you have.

 

I appreciate your input. I checked all the fuses already, no dice.

 

So when you open the drivers door the overhead cabin lights come on? Fuse 9 powers that light, the siren (which I hope you have disconnected until this locking problem is sorted out) and the Tow Away Alarm Switch which connects to the CLS. I pulled my fuse 9 this morning and when using the fob to try and lock the car I could not lock/unlock, but the lights did flash as normal. Please double check fuse 9 as a bad fuse there exhibits your problems.

Fuse 35 should give hot power 12v to the SKREEM at all times. There is a RD/YL wire from the 35 fuse to connector C1 #18 on the SKREEM. If you have power at that connector I would suspect the SKREEM is not working properly with it's communication to the BCM and thus you can't lock the doors. You could contact the Mercedes Swap Shop for help with the SKREEM. There is also a remote keyless entry relay that is powered off fuse 35. I believe it is yellow colored and it is located in the under hood fuse box. It to has a RD/YL wire that feeds it power and the output goes to the SKREEM at C1 #2.

Without a scan from a DRB III or an emulator this is much harder to pin point.

 

Thanks very much for your expertise.
I'm away on a trip now - when I get home I'll run through the fuses again and test that relay.
For now I'm happy knowing the hatch is locked. Maybe your suggestions will lead me to a real solution.

 

Oh, and I forgot to thank you specifically for your experiment with the fuse. Above and beyond.

 

Okay, zip!
Before I got home I was convinced you had it figured out. (Sidebar: yes, the interior lights were inoperative. I never mentioned it before because I put it down to the numerous badly-executed modifications. I'm talking drooping wires, solder blobs in the carpets, drippy polyurethane glue deposits, partially removed projects, etc. Lesson learned - don't withhold *any* symptoms when asking for diagnostic help).
I had already checked all the fuses, but honestly paid more attention to #25 and 26 which seemed more pertinent.
So, I looked at #9 again, looked perfectly fine. I put a multimeter on it and got the continuity "beeep." I also had enough sense to look at the actual resistance number, and it showed a couple ohms resistance. I don't think it ever actually blew. Looks more like a crack where the loop joins the vertical part. Very deceptive.
Anyway, new fuse and all is normal, including the fuel door lock and interior lights. I'm very relieved and grateful for the help.
Then it threw a misfire code which won't clear. Oy.

 

I just had the same thing happen with my number 9 fuse. I just ordered a fuse kit and I'm going to replace all of those 20 year old fuses.