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E30/E28 central locking FAQ
This FAQ covers central locking on E30 (3 series '84-'91) and
E28 (5 series '82-'88) cars.
It also seems to apply to E24 (6 series '76-'89) and maybe others
(?)
1.0 Introduction
2.0 Functional Overview
3.0 Common Problems and how to fix them
3.1 Drivers Side Door lock cylinder
3.2 Intermittent locks, non-working central locking
3.3 Burnt out door lock actuator motors
3.4 Central locking works but unlocks a second or two later
4.0 Related Accessories
4.1 Alarm
4.2 Door lock heater
4.3 Interior light with delay
5.0 Door Lock Repair Kit Instructions
6.0 Central locking troubleshooting guide
7.0 Driver's Door Jamb Plug
1.0 Introduction
Lock system/ production years/ models
Central locking was standard, but early models (<'85) do not have
the double-lock feature. Starting somewhere in 1985 model year,
the double lock feature became standard. Actually, it seems that
the double lock feature was used in all E30's with production
date 9/84 and up. E28's seemed to start 1/85 or mid year
production.
Early models had keys marked with an 'I' and where shorter, using
a 4 digit key code. Later models are marked with an 'S' and have
longer keys with a 5 digit key code. The double-lock feature is
engaged with the last section of the key - the valet key is
shorter than the regular keys and does not engage the double
lock.
2.0 Functional Overview ( by Paul Reitz prreitz_at_amp.com BMW CCA
#1167)
Intended Operation:
The system allows the entire car to be locked from either front
door key lock, the trunk key lock, or by depressing the driver's
door lock button inside the car. It also allows the car to be
double-locked (from the driver's side key lock) so an intruder
cannot unlock the car just by breaking a window or using a tool
to lift one of the door lock buttons. If the car is locked - but
not double-locked - it can be unlocked via the key lock from
either front door or the trunk, or by lifting either front door
lock button from the inside. The doors automatically unlock via
an inertia switch that operates on impact greater than 5g. Door
lock buttons on 4 door models have no control over central
locking, although they can lock, and under certain circumstances
unlock that particular door. Never double-lock a car with
occupants inside!
The system consists of the following components:
Key lock cylinders in each front door (and the trunk), which
operate the door latches that prevent the door handles from
operating, and which in turn have mechanical linkages to the door
lock button and to the door lock motor unit mounted inside the
door cavity. (There is also a trunk lid lock motor unit that
locks the trunk latch button, and a gas filler lock motor.) Most
door lock motor units have two motors: the door lock motor, which
operates the door latch locking mechanism and door lock button,
and the double-lock motor, which "pins" the mechanical linkages
and the door latch so they cannot be manually unlocked. The
driver's door and trunk lack the double-lock motor; the trunk
doesn't need one, since there's no "lock button" there, and the
driver's door is double-locked by the mechanical constraint of
the 90 degree position of the key lock cylinder. The door lock
motor unit also contains the lock and unlock switches which send
"lock" and "unlock" signals to the Central Lock Control Unit
(CLCU). The CLCU contains some electronics and the LOCK and
UNLOCK relays, each of which has a set of normally-open and
normally-closed contacts with a common connection,
and which operate all door motors. The CLCU is located
behind the speaker in the left front kick panel.
In addition, there are microswitches mounted on the front door
key lock cylinders. On the driver's door, this is the "unlock
inhibit" microswitch, which closes only when the key lock
cylinder is rotated to the 90 degree position, and initiates
double-locking. A similarly positioned microswitch in the front
passenger's door is operated at the 45 degree key position, but
is used for unlocking only.
Locking and Unlocking:
when a door or trunk key lock is turned 45 degrees, or the
driver's door lock button is depressed, linkages move to close a
"Lock" switch contact in the respective door lock motor unit.
This contact grounds the Lock input on the CLCU, which, if the
car is presently unlocked, momentarily energizes the "LOCK"
relay. This relay has a normally closed (NC) contact and a
normally open (NO) contact, with a common connection.
(Technically, an SPDT relay.) The common is wired to one side of
all door lock and double-lock motors; the NC contact goes to
ground, and the NO contact goes to +12 volts via fuse #27. When
the relay operates, current flows through the (now closed) NO
contact, through the door lock motors to ground through the
other, unenergized relay's (still closed) NC contact. The motors
run to a physical limit and stall; the relay is de-energized
after about 1 second, and current flow ceases.
Unlocking operates analogously, via "Unlock" switches and the
UNLOCK relay. The manner of operation of the Lock and Unlock
relays is to just reverse the polarity of power applied to the
door lock and double-lock motors,except that the UNLOCK relay
contact common is not wired directly to the double-lock motors.
Only one relay operates at a time.
One side of all door lock and double-lock motors is connected to
the LOCK relay common, but the other connection of the
double-lock motors is to pin 11 of the CLCU, which is at the
junction of two "steering" diodes. One of these diodes is
connected to the "unlock inhibit" input (pin 10 of the CLCU), and
provides a ground return for the double-lock motors only when the
driver's door microswitch has been closed (by turning the key
lock to 90 degrees.)
Although the passenger's door lock motor unit contains both
"lock" and "unlock" contacts, only the "lock" contact is
connected. This allows the passenger to lock the entire car from
the inside, but not to unlock it. Unlocking from the passenger's
side can only be done by closing the microswitch in the
passenger's door with the key, from outside the vehicle.
If the car is double-locked, the passengers' door double-lock
motor prevents the key lock from being rotated so the car can
only be unlocked from the driver's door.
Double-locking:
The front passenger (and any rear door) door lock motor units
contain a double-lock motor. When it is activated, it
mechanically locks the linkages themselves, preventing the door
lock buttons from being lifted, thus making unauthorized entry
more difficult.
When the driver's door key lock is first rotated to 45 degrees
and the "Lock" relay operates, 12 volts is applied to the
double-lock motors via the LOCK relay common, but the other
double-lock motor connection via the diode junction offers no
return path to ground, so the double-lock motors do not operate.
When the driver's door lock key is turned to 90 degrees, it
closes the "unlock inhibit" microswitch, which grounds the
"unlock inhibit request input", CLCU pin 10. Now, a complete
return path is created from the double-lock motors to ground via
pin 11, through the diode to pin 10, through the (closed) unlock
inhibit microswitch. The closure to ground of the microswitch
also signals the "unlock inhibit request", which operates the
"LOCK" relay. This time, because of the ground return through
the steering diode, the double-lock motors also operate, and the
door lock linkages are latched in the locked position.
The driver's door itself does not have a double-lock motor;
removing the door key in the 90 degree position jams that door's
latch (and lock button), serving the same function. The
grounded unlock inhibit microswitch prevents the trunk key lock
from creating an unlock event.
Unlocking a double-locked car:
This action can only be initiated from the driver's door key
lock. When the key is rotated CCW from its double-locked
position, it releases the ground connection of the unlock inhibit
microswitch. (Actually, once this is done, the trunk key lock
can also be used to unlock the car.) As the key is rotated
another 90 degrees CCW, it mechanically unlocks the door latch,
raises the door lock button and moves the door lock linkage to a
position that closes an unlock switch. The "UNLOCK" relay
operates, and unlocks all doors. (During any UNLOCK relay
operation, 12 volts is also applied to the second steering diode,
which allows the double-lock motors to operate.) The current
return path to ground from all lock and double-lock motors is via
their connection to the (unenergized) LOCK relay NC contact to
ground. The double lock motors operate quickly enough to also
allow the door lock motors to operate.
3.0 Common Problems
3.1 Drivers Side Door lock cylinder
A common problem is that the door lock cylinder does not turn
properly. It either can't turn past 45 degrees ( all the way to
90 degrees clockwise to engage double lock ) or it won't turn
back and unlock the door properly.
Also, various parts of the lock cylinder mechanism crack, fall
apart, bend, and springs get too weak.
Remember, the drivers door should LOCK completely mechanically
(ie you can disconnect the battery and check this out) by turning
the key 45 degrees to the right.
If it doesn't quite lock, or takes a few tries to get the lock
button to go down completely, then the lock cylinder probably
needs replacing.
If you also can't turn the key past 45 degrees, it probably means
the lock cylinder needs replacing.
BMW has something called "Door Lock w/key repair kit" or
something like that, BMW part number 51211924903 or maybe
51-21-9-061-343. Both have been reported as correct so who knows?
Anyway, it should cost around $30 (us) from a dealer. It comes
with a new lock cylinder, and all possible tumbler combinations
so you can key it to your existing key. I have included the
translated german instructions at the end of the FAQ.
3.2 Intermittent locks, non-working central locking, buzzing
from the lock relays
Check the connector from the drivers door to the A pillar. Pull
back the rubber boot and pull apart the connector. It is often
full of corrosion and the pins no longer make contact.
Pins and sockets are available from BMW ($0.50 each?) or possibly
from your local electronics store. They are the same pins and
sockets as in AMP CPC connectors.
Pull out the corroded pins, cut and solder on new ones and put
back in the connector.
Pin-out for the sockets are at the end of this FAQ.
3.3 Burnt out door lock actuator motors
Test to see if the +12v and -12v signals are getting to the door
lock actuator motor. If so and the motor doesn't move, replace.
Note that drivers door is different than passenger side door is
different than trunk and gas latch.
housing --> upper lower
drivers door White Red
passenger Red Red
rear doors Red White
Trunk White Red
3.4 Central locking works but unlocks a second or two later.
If you lock the doors and they unlock again almost immediately it
is because there is a problem. A motor is dead or something is
jammed. The central locking is telling you that everything is not
locking properly. Find out if all motors work, make sure there
are no bent rods or things jamming the mechanism.
4.0 Getting inside a door and removing the door lock cylinder
remove arm rest ( 2 screws )
remove power mirror control (pull out) and remove screw in behind
remove door lock button
remove door latch trim piece (push to the right or left and it
should pop off)
pull panel away from door sides and bottom. I use my fingers. It
will pop out plastic snaps. Lift panel up to detach lip from top
of door.
peel back sticky plastic barrier
now, a 2 door has much more room inside than a 4 door.
either way, if you remove the bottom nut on the window channel
you can move the channel around to get it out of the way.
Outside the door undo the screws holding the handle on.
Inside the door undo the two bolts holding the handle mechanism
to the door. Wiggle and swear until you remove the mechanism.
You then have free access to the door lock cylinder. There is a
'clip' which pulls off to the right. Once that is off, the
cylinder can be removed from outside of the door.
Many people have then found that the cylinder mechanism has
- a bent arm - they bent it straight and it worked fine after
that
- a cracked arm - replace cylinder assembly
- weak springs (put key in and try out the mechanism)
- something else broken.
You can also check your latch mechanism still inside the door -
it should work freely with no binding.
4.0 Related Accessories
4.1 Alarm
BMW Factory alarm consists of hood sensor, trunk sensor, door
sensors, ultrasonic motion sensor. It arms when the double lock
is activated. It includes an ignition kill, flashes the lights,
and honks the horn when triggered.
4.2 Door lock heater
Often disconnected, broken, or stuck in the 'on' position leading
to possible fire. When pulling up on drivers side door latch, a
ground connection is made at the heater module. This signals the
central locking to send 12V to a resistor mounted in the clip
holding the lock cylinder to the car. To operate: lift and hold
latch.
4.3 Interior light with delay
Mounted in place of door lock heater. When handle is lifted for
entry to car, a timer is set to keep interior lights on for a
short amount of time.
5.0 Door Lock Repair Kit Instructions
Remove door lock cylinder as previously described.
BMW instructions are as follows:
Before assembling, fill the lock channels of the key cylinder
with the enclosed lubricant.
Insert the lock and the lock springs corresponding to the code
list or the key in question.
Build the lock cylinder according to the drawing.
Hints:
To make assembly easier, grease the roller and the accompanying
'N'.
Lead the 'N' into the leading ring.
Pay attention to the lock in the cylinder.
Carefully with light hammer blows, lead it in.
Put the dead-point-spring in place and tighten.
6.0 Central locking troubleshooting guide (by Jim Conforti)
Start with doors unlocked and all windows open
NOTE: NEVER CONNECT OR DISCONNECT THE CONTROL UNIT UNLESS BATTERY
POWER IS
REMOVED!!
Operation Response Action
1 DDL to lock All doors lock Goto OP #2
Some doors Lock R/R suspect Door Lock Motor ckt.
No doors Lock Goto OP #4
2. DDL to deadbolt All doors double lock Goto OP #3
Drivers and SOME others dbl lock R/R suspect Door Lock
Motor
Drivers ONLY dbl locks Perform TEST B
Drivers does NOT dbl lock Mechanical Problem
3. DDL to unlock All doors unlock Goto OP #4
Some doors unlock R/R suspect Door Lock Motor ckt.
No doors unlock Goto OP #5
4. PDL to lock All doors lock If doors did not lock in
OP #1 R/R DD lock switch
else Goto OP #5
Some doors lock R/R suspect Door Lock Motor ckt
No doors lock If doors locked in OP #1 R/R PD microswitch
if doors did not lock in OP #1 perform TEST A
5. PDL to lock All doors unlock If doors did not
unlock in
OP #3 R/R DD lock switch
else Goto OP #6
Some doors unlock R/R suspect Door Lock Motor No doors
unlock If
doors unlocked in OP #3 R/R PD Lock Switch
if doors did not unlock in OP #3 perform TEST C
6. Get in car, close/lock all Doors remain locked
Goto OP #7
doors, IGN to RUN Doors Unlock R/R Central Locking
control unit
7. Get out, DDL to lock All doors can be unlocked Goto OP
#8
Unlock each door by All doors remain secure Disconnect
connector from
control unit and check
pulling up button for short to ground at terminal #11
if short, find it!, if not R/R Control Unit
8. Trunk lock to LOCK Trunk Locks Goto OP #9
Trunk does not lock If doors lock, R/R Trunk lock motor
and/or circuit
If doors do not lock R/R Trunck lock switch
R/R Control Unit if switch and circuit are OK
9. Trunk lock to UNLOCK Trunk unlocks Goto OP #10
Trunk does not unlock If doors unlock, R/R Trunk lock motor
and/or circuit
If doors do not unlock, R/R Trunk lock switch
R/R Control Unit if switch and circuit are OK
10. Turn key back to LOCK Gas filler locks Goto OP #11
Gas filler does not lock R/R Gas Filler Motor ckt.
11. Turn key to unlock Gas filler unlocks Done, No
faults!
Gas filler does not unlock R/R Gas Filler Motor ckt.
TEST A.
Measure Voltage at Control Unit Connector w/ Control Unit
Connected
Term 3 and Ground should be battery, else check wire to Term 3
for open
Term 3 & 4 should be battery, else check wire from Term 4 for
open to
ground
Jumper between Term 7 and ground, if doors lock R/R switches and
related
wiring else ...
Disc. battery, remove Control Unit and reconnect Batt. jumper 1 &
3
together, now jumper 2 & 4 together if doors lock, R/R Control
unit, else
check wires on Term. 1 & 3 for opens (see schematic)
TEST B.
With Conrol Unit connected, jumper between 10 & ground doors
should double
lock, if not, check wires to Term. 11 for opens and R/R Control
Unit if no
opens found. If doors DO double lock, check wires to Term 10 for
open and
R/R Unlock Inhibit Switch if wire OK.
TEST C
With Control Unit connected, Jumper 6 & ground. If doors unlock,
R/R
switches and related wiring (see schematic) if doors do NOT
unlock R/R
Control Unit
7.0 Driver's Door Jamb Plug (from iX ETM)
In-Car Connector:
pin colour function
1 gn/wt fuse 19 pwr to mirrors + int.lt.cancel
2 br int.light GND door handle switch
3 rd int.light timer, centr.lock cntrl pwr
4
5 bu/bk pwr passenger mirror motor
6 bu/wt pwr passenger mirror motor
7 wt/bk switched pwr to passenger mirror clutch
8 br GND central lock control, double lock
9 bu pwr/return door lock motor
10 wt return/pwr door lock motor
11 yl/bu lock' request
12 gr/bu unlock' request
13 vi pwr window motor
14 bk pwr window motor
15 rd/bk int.light timer, central lock pwr
16
17 rd/br double lock' request
18 gn/wh fuse 19 pwr interior light cancel
19 br/gn int.light enable
20 gy/gn radio speaker
21 gy/yl radio speaker
note: colours bk=black, br=brown, rd=red, yl=yellow, gn=green,
bl=blue, vi=violet, gy=grey, wt=white
note2: colours not used in all years/models, this is a general
guide only!
note3: some cars have lock heaters, some have interior light
timers, probably in an either or' situation.
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