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BMW E39 Trunk Latch Testing and Replacement
 
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Pelican Technical Article:

BMW E39 Trunk Latch Testing and Replacement

Kerry Jonsson

Time:

3 hours3 hrs

Tab:

$100

Talent:

****

Tools:

Panel removal tool, Door panel clip removal tool, T30 socket, Phillips head screwdriver

Applicable Models:

BMW 525i Sedan (2001-03)
BMW 528i Sedan (1997-00)
BMW 530i Sedan (2001-03)
BMW 540i Sedan (1997-03)
BMW M5 Sedan (2000-03)

Parts Required:

Trunk latch, plastic mounting clips

Hot Tip:

This will also help with a battery drain because the trunk light is left on.

Performance Gain:

Get the trunk latch working both mechanically and electrically

Complementary Modification:

Access to the trunk

The trunk latch does more than just lock the trunk closed. It has an actuator that unlocks the trunk either from your key fob or manually with the key lock cylinder. Built into the actuator is an interior light switch. This light switch turns on two trunk lights that illuminate when the trunk is open. They go out when the latch is closed. This this switch fails the trunk light will stay on and the battery will drain overnight. Here we are going to cover removing the trunk latch and testing it.

Open your trunk.

In order to access the trunk latch and actuator you need to remove the plastic and carpet trunk covers. There is a combination of plastic pop rivets and Phillips screws holding the covers on.

First remove the trunk trim panel rivets using a trim panel tool.
Figure 1

First remove the trunk trim panel rivets using a trim panel tool. You only have to remove the clips along edge of trunk lid. (green arrows) Then, unscrew and open the tool kit (yellow arrow).

To remove the trunk trim panel rivets, pry the center out of the rivet using a trim panel tool and remove rivet from the trim panel.
Figure 2

To remove the trunk trim panel rivets, pry the center out of the rivet using a trim panel tool and remove rivet from the trim panel.

Next, remove the small plastic cover located inside the handle on the left side of the trunk lid.
Figure 3

Next, remove the small plastic cover located inside the handle on the left side of the trunk lid. (green arrow) Then remove the Phillips head screw under the cover (yellow arrow).

Now you will have to unclip the four trim panel clips that run along the bottom of the plastic trim panel.
Figure 4

Now you will have to unclip the four trim panel clips that run along the bottom of the plastic trim panel. (green arrows) This photo shows the locations of the clips already detached from trunk lid. Use a trim panel tool to release the clips.

Lever out the trunk light lens using a flathead screwdriver.
Figure 5

Lever out the trunk light lens using a flathead screwdriver. Then disconnect the electrical connector (green arrow) by pulling it straight out of light.

Next you have to remove the carpet panel on the trunk lid.
Figure 6

Next you have to remove the carpet panel on the trunk lid. Remove four Phillips head screws (green arrows), then disconnect trim panel clips at each corner (yellow arrows). Pull carpet trim away from trunk lid.

Remove the three T30 Torx screws (green arrows) that mount the trunk latch to the trunk.
Figure 7

Remove the three T30 Torx screws (green arrows) that mount the trunk latch to the trunk.

Pull the latch out from the inside panel.
Figure 8

Pull the latch out from the inside panel. It is not going to come out all the way until you unplug the electrical connector (green arrow on right) and unhook the linkage (green arrow on left) from the latch.

Squeeze the connector and pull it straight away from the latch.
Figure 9

Squeeze the connector and pull it straight away from the latch. Once the latch is out we are going to plug this connector back in to do our testing.

Twist the latch to unhook the linkage (green arrow).
Figure 10

Twist the latch to unhook the linkage (green arrow). Now you can remove the latch. If you are going to test the electrical circuits you can plug the latch back in. Installing is reverse of removal. Hook the latch onto the linkage first, plug in the electrical connector and position the latch and bolt it down. You can now put the panels back on

These are the 4 wires that operate the latch.
Figure 11

These are the 4 wires that operate the latch. They Grey/Green tracer wire (green arrow) is the wire that powers up the actuator to open it. The Brown wire (yellow arrow) is the ground wire for the latch. The Grey/Brown tracer (blue arrow) is the latch position switch that goes to the body module (GEM). The White/Brown tracer is the wire that controls the trunk mounted lights. The wire colors mentioned here applied to the vehicle I was working on. I suggest having an up to date wiring diagram on hand when diagnosing. This way you are sure you are on the right wires.

The light in the trunk will be on.
Figure 12

The light in the trunk will be on. You can use a screwdriver to move the latch to the closed position. The trunk light should go off at this point.

This is the trunk latch in the closed position (lower red arrow).
Figure 13

This is the trunk latch in the closed position (lower red arrow). Notice the position of the actuator on the latch is moved all the way in (upper red arrow)

Push the trunk release button on the outside of the trunk.
Figure 14

Push the trunk release button on the outside of the trunk. For testing see tech article Testing Trunk Release Button to verify it is working.

If the trunk latch is working properly the latch will move to the unlocked position (lower red arrow) as a result of the actuator (upper red arrow) extending.
Figure 15

If the trunk latch is working properly the latch will move to the unlocked position (lower red arrow) as a result of the actuator (upper red arrow) extending.

You can test the manual trunk key switch (red arrow) as you turn the key from lock to unlock the linkage should move from left to right
Figure 16

You can test the manual trunk key switch (red arrow) as you turn the key from lock to unlock the linkage should move from left to right

The manual trunk key switch has three wires to signal the body module (GEM) when someone has locked or unlocked the trunk.
Figure 17

The manual trunk key switch has three wires to signal the body module (GEM) when someone has locked or unlocked the trunk. The body module (GEM ) will also lock or unlock all the doors of the car when you do this. The Brown/Blue tracer (green arrow) changes voltage when the key is in either the lock or unlock position. The Brown/Yellow tracer will change voltage only in the unlock position. The Red/Black tracer is the voltage supply for the switch. The wire colors mentioned here applied to the vehicle I was working on. I suggest having an up to date wiring diagram on hand when diagnosing. This way you are sure you are on the right wires.

Here we have the red lead of our meter in the power supply for the actuator and the black lead of our meter in the ground wire.
Figure 18

Here we have the red lead of our meter in the power supply for the actuator and the black lead of our meter in the ground wire. In order to get any solenoid to function you need to supply a power and a ground. During this test, be sure your test leads do not touch each other. You could blow a fuse.

You can push the trunk release switch again and measure the voltage to the actuator.
Figure 19

You can push the trunk release switch again and measure the voltage to the actuator. DonÂ't be surprised if the voltage does not go all the way to battery voltage and that is okay.

We have now moved our red test lead to the White/Brown tracer (trunk illumination) with the latch in the open position the wire is switched to ground through the latch.
Figure 20

We have now moved our red test lead to the White/Brown tracer (trunk illumination) with the latch in the open position the wire is switched to ground through the latch. Notice how the meter says about 0 volts. Keep in mind the black lead is still attached to the Brown wire. The wire colors mentioned here applied to the vehicle I was working on. I suggest having an up to date wiring diagram on hand when diagnosing. This way you are sure you are on the right wires.

Use a screwdriver to close the latch (lower red arrow) and if the illumination switch in the latch is working it will open and you will measure about 12 volts on the wire (upper red arrow).
Figure 21

Use a screwdriver to close the latch (lower red arrow) and if the illumination switch in the latch is working it will open and you will measure about 12 volts on the wire (upper red arrow). This is a good switch. The logic is if the trunk latch is open the wire will go ground and turn on the trunk light. If the latch is closed the circuit will open and the trunk light will go off.

We have now moved our red test lead to Grey/Brown tracer.
Figure 22

We have now moved our red test lead to Grey/Brown tracer. This is the wire that tells the body module (GEM) if the trunk latch is closed or not. (This way if the trunk is open it can warn the driver with a message in the instrument cluster) With the latch in the open position (lower red arrow) you should measure close to 5 volts on the wire. Here we only measure 3.5volts but that is okay. The wire colors mentioned here applied to the vehicle I was working on. I suggest having an up to date wiring diagram on hand when diagnosing. This way you are sure you are on the right wires.

When we move the latch to the locked position with our screwdriver (lower red arrow) we see the measured voltage drop to ground (0volts) (upper red arrow).
Figure 23

When we move the latch to the locked position with our screwdriver (lower red arrow) we see the measured voltage drop to ground (0volts) (upper red arrow). Keep in mind the black lead is still attached to the Brown wire. The logic is when the GEM sees 5 volts it knows the trunk is open. When it sees 0 volts it knows the trunk is closed. This is a good switch.

If you want to test the manual trunk key switch put the red lead of your meter in the Red/Black tracer (blue arrow) and put the black lead on a ground.
Figure 24

If you want to test the manual trunk key switch put the red lead of your meter in the Red/Black tracer (blue arrow) and put the black lead on a ground. You can use the brown wire at the trunk latch actuator, the body of the car (not covered with paint and the battery negative terminal for your ground connection. You should measure battery voltage. Move your red lead to the Brown/Blue tracer you will see battery voltage by moving the key in either the lock or unlock position. Move the red test lead to the Brown/Yellow tracer and you will see battery voltage with the key only in the lock position. The logic is when the GEM sees voltage on both wires of the switch is knows the key is turned in the lock position. If the GEM sees voltage on only the Brown/Blue and not on the Brown/Yellow the key must be in the unlock position. That is how it knows what position the key is in. The wire colors mentioned here applied to the vehicle I was working on. I suggest having an up to date wiring diagram on hand when diagnosing. This way you are sure you are on the right wires. Installing is reverse of removal. Hook the latch onto the linkage first, plug in the electrical connector and position the latch and bolt it down. You can now put the panels back on

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Comments and Suggestions:
4BLU Comments: ..."AINT NOBODY GOT TIME FOR THIS"!I JUST BOUGHT USED PLZ HELP WITH WAYS4 ME 2 FIND INFO SPECIFIC MY '03 325CI COUPE
October 21, 2016
  Followup from the Pelican Staff:

I would grab a repair manual. It will have info on your model.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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Page last updated: Sat 12/3/2016 02:05:36 AM