1995 525i (E34) truck central locking question

[cwilliamhicks]

I bought this thing used about a year ago - generally good condition inside and out, just minor fixes here and there. Right now I'm in the midst of replacing anything with "cooling" in its name, but that's another story!

The truck lock cylinder has always successfully locked the entire car, and is always locked/unlocked by either of the front locks and plungers. A few times now I've been able to centrally UNLOCK the car from the truck cylinder.

Since I can't tell what's a malfunction and what's stock behavior, how is this supposed to behave? Am I supposed to be able to unlock the car with the trunk, or is this something shorting out?

The wiring diagram isn't all that helpful since it just describes the connections from the lock to the ZKE module. Also remember, I have the 1995 that has a slightly-different self-deadbolting ZKE. Go figure on that one.

Thanks!

[demetk]

Yes, you should be able to lock & unlock via the trunk lock. I had a bad fuse that was causing that type of behavior.

[Tre0Tre34]

When you find your blown fuse, check the wiring going into your trunk lid. The insulation is probably cracked on a few of the wires and is a common fault when having trouble with things like door locks and interior lights.

[cwilliamhicks]

Whoa, this just keeps getting stranger.

I actually already spliced in some extra wire in the trunk-lid loop - they were bent/re-bent to the point of breaking and I already had flickering trunk lights give that problem away. That's no longer a problem as far as I can tell.

Here's a couple tests I did to expose just how crazy this is:

The most basic of tests:
Unlock car with driver's side lock: car centrally unlocks.
Lock car with driver's side lock: car centrally locks (everything locks)

Cool. Now the same for the passenger side:
Unlock car with passenger's side lock: car centrally unlocks.
Lock car with passenger's side lock: car centrally locks.

Now to the trunk:
Unlock the trunk: car centrally unlocks.
Lock the trunk: car centrally locks.
Unlock the trunk: central locking does nothing, only the truck is unlocked manually
Lock the trunk: central locking does nothing (car is still locked) and now the truck is manually locked again.

So naturally I did this a few times - lock/unlock the car from the driver's side, then try the trunk. Then again from the passenger side, back to the trunk.

Going back to unlocking/locking from the passenger side and the trunk lock will centrally unlock/lock the car, but just once.

Whaaaaat?! So the general module is getting the signal from the trunk - lock, and unlock... but it'll only once... until you unlock/lock from the passenger side... but not the driver's side... weird. The trunk always reliably centrally locks the car, no matter what. This "just once" behavior is limited to unlocking.

Now: I know the 90's electronics modules are programmable-logic voodoo. You can see this if you put the windows auto-down and lock the doors with your elbow: the windows pause for the doors to lock, then continue down. Why? because a little 8-bit dorito of a computer chip is handling dozens of inputs/outputs in a round-robin. Same thing with the aloha lights when you shut down in the dark - turn the lights off, parking brake on, clutch, gear, ignition off... and the lights come on inside. Do it in any other order/timing and it won't happen. However Hans programmed it back in Bavaria is how it works with these old systems.

So, is this lock behavior normal kinds of crazy or is something actually broken?

[Binjammin]

I bought this thing used about a year ago - generally good condition inside and out, just minor fixes here and there. Right now I'm in the midst of replacing anything with "cooling" in its name, but that's another story!

The truck lock cylinder has always successfully locked the entire car, and is always locked/unlocked by either of the front locks and plungers. A few times now I've been able to centrally UNLOCK the car from the truck cylinder.

Since I can't tell what's a malfunction and what's stock behavior, how is this supposed to behave? Am I supposed to be able to unlock the car with the trunk, or is this something shorting out?

The wiring diagram isn't all that helpful since it just describes the connections from the lock to the ZKE module. Also remember, I have the 1995 that has a slightly-different self-deadbolting ZKE. Go figure on that one.

Thanks!


Whoa, this just keeps getting stranger.

I actually already spliced in some extra wire in the trunk-lid loop - they were bent/re-bent to the point of breaking and I already had flickering trunk lights give that problem away. That's no longer a problem as far as I can tell.

Here's a couple tests I did to expose just how crazy this is:

The most basic of tests:
Unlock car with driver's side lock: car centrally unlocks.
Lock car with driver's side lock: car centrally locks (everything locks)

Cool. Now the same for the passenger side:
Unlock car with passenger's side lock: car centrally unlocks.
Lock car with passenger's side lock: car centrally locks.

Now to the trunk:
Unlock the trunk: car centrally unlocks.
Lock the trunk: car centrally locks.
Unlock the trunk: central locking does nothing, only the truck is unlocked manually
Lock the trunk: central locking does nothing (car is still locked) and now the truck is manually locked again.

So naturally I did this a few times - lock/unlock the car from the driver's side, then try the trunk. Then again from the passenger side, back to the trunk.

Going back to unlocking/locking from the passenger side and the trunk lock will centrally unlock/lock the car, but just once.

Whaaaaat?! So the general module is getting the signal from the trunk - lock, and unlock... but it'll only once... until you unlock/lock from the passenger side... but not the driver's side... weird. The trunk always reliably centrally locks the car, no matter what. This "just once" behavior is limited to unlocking.

Now: I know the 90's electronics modules are programmable-logic voodoo. You can see this if you put the windows auto-down and lock the doors with your elbow: the windows pause for the doors to lock, then continue down. Why? because a little 8-bit dorito of a computer chip is handling dozens of inputs/outputs in a round-robin. Same thing with the aloha lights when you shut down in the dark - turn the lights off, parking brake on, clutch, gear, ignition off... and the lights come on inside. Do it in any other order/timing and it won't happen. However Hans programmed it back in Bavaria is how it works with these old systems.

So, is this lock behavior normal kinds of crazy or is something actually broken?

http://i2.cdn.turner.com/money/dam/assets/130513130803-trucks-gallery-intro-620xb.jpg

http://static.ddmcdn.com/gif/half-ton-truck-1.jpg

http://www.deltatruckequipment.com/wp-content/uploads/2010/05/Laidlaw-Truck.jpg

http://imagenes.es.sftcdn.net/es/scrn/88000/88298/truck-racing-1.jpg?key=api

http://www.dcfd.com/Apparatus/Truck15/Truck15_01.jpg

Pull your trunk lock cylinder and inspect all the wiring to it. Put a meter on the wiring while you turn the key in the trunk and when it fails to lock, see if it's actually doing something or if the issue is just at the lock cylinder. Don't assume it's got anything to do with the GM.

[cwilliamhicks]

BAHAHAHHAHA - good catch! I'm not even going to edit the original post, that was too good.

Good next step - I'm going to check Pin 23 and Pin 17 at the general module connector X255 while locking/unlocking the trunk (not truck!) cylinder to make sure it's definitively getting voltage every time. If it isn't, then there's something wonky either in the wiring from the cylinder or the lock switch itself.

It's just so strange that it reliably works after being cycled from the passenger side, but not the driver's side.

EDIT: tried to post some photos, and it blew up with random text
Let's try this again:

500325500326500327

[cwilliamhicks]

Whoops - the photos I uploaded blew up. I edited the previous post an embedded the images differently.

[Binjammin]

Do you know how to use photobucket?

[cwilliamhicks]

I'm new to the forum so I've just realized that photobucket is what people tend to use here. I just uploaded the photos as attachments - just shots of the electrical diagrams I'm using in case someone comes across this thread looking for a similar problem - I'd like it to be helpful!

[Binjammin]

I'm new to the forum so I've just realized that photobucket is what people tend to use here. I just uploaded the photos as attachments - just shots of the electrical diagrams I'm using in case someone comes across this thread looking for a similar problem - I'd like it to be helpful!

Yeah, that's all good, I just meant that it's easier to link to pictures hosted elsewhere than to upload pics.