Quote:
Originally Posted by HIGHCOUNTRYMIKE
I have the 03 E350 SMB:
Similar locking, unlocking randomly.......removed the the auto door locking control system.
End of random lock, lock, locking.
I can auto lock all doors from drivers side but unable to unlock.....I live with it.
2003 E350 SMB RB50 4X4 7.3 304,000 m.
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Well, I just spent a couple hours fiddling with this.
The problem was not the rear door lock switch. I found this switch wasn't even working, so I just disconnected it.
I found the control unit. In my 2004, it's located just in front of the passenger door, under the dash. It has two connectors. The smaller connector appears to be the output -- power going out to the door lock solenoids. The larger connector appears to be the input -- control lines from the switches. If the larger connector is disconnected, the door switches won't work, but the keyfob remote still works to control the locks -- as the radio receiver is inside the control unit. And the random auto-locking problem stops.
The door lock switches work by grounding the signal wire. But grounding the "lock" button (pink-with-yellow-stripe wire) doesn't cause the doors to lock. Checking with my multimeter shows 300 ohms when not pressed. I presume this is close enough to "grounded" to cause the control unit to think the button is pressed (almost) all the time. Plugging in the input connector to the control unit also causes the door locks to lock one time just as the plug is inserted.
So I presume that a wire somewhere has worn through and is partially grounding the connection. Looking around under the dash, there are plenty of wires which have been rubbing against the painted metal body surfaces over the years, and have worn the body paint away to bare metal. (I guess 200+ hours of nasty washboard will do this!) But at least these wires, the ones I checked, still seem to have their insulation intact.
I found next to the lock control unit are some connector plugs -- for the rear door, and also the passenger door. Disconnecting each of these plugs did not fix the problem. Therefore I presume the problem is with the connection to the driver door, which travels inside dash. (There is no plug to try disconnecting for this part of the circuit.) I ended up snipping the pink-with-yellow wire to stop the constant random locking for now, but it looks like I will need to dig into the dash at some point to finally solve this problem (or simply hack in a new bypass wire to the driver door). (And, yes, the photo shows that I accidentally also snipped the
red-with-yellow wire too -- they looked so similar!) Grounding the cut tip of the remaining pink-with-yellow wire going up to the control box now does work to lock the doors.
AWOL
Linear Mode
