DIY: E90 Lumbar Support Retrofit - BMW 3-Series (E90 E92) Forum

This is the installation of the driver side lumbar support in a 2006 BMW 330i with existing side bolster support (sport package).

I ordered the individual connectors, pins, and bushings for the new harnesses (details later). The dealer told me that the lumbar wiring might* be included with an entire new seat harness (p/n: 61 12 6 942 559), but this is unverified as it needed to be ordered from Germany.

There is no programming needed since the lumbar and side bolsters are not involved in the seat memory.

Tools:
Trim Removal Tool / Medium Gauge Wire Cutters
Soldering Iron
Solder
Heat Shrink Tubing
Wire Fish (really helps!)

Parts Needed:
1x Lordosis Pad - 52 10 7 140 555
1x Pump and new valves - 52 10 7 138 786
2x Universal Socket HO - 61 13 6 909 058
14x Bushing Contact - 61 13 0 006 663
4x Pin Contact - 61 13 0 006 664

The pins and bushing contacts come with several inches of wire attached which is enough to build the harnesses; no extra wire is necessary.

Here we go:

Before doing this, make sure to disconnect the battery and wait at least 60 seconds before disconnecting anything.

I removed the entire seat so I could see what wiring was already in place, since the dealer couldn't tell me for sure. There are four torx screws and one large yellow connector (airbags, etc) which need to be removed.

If you decide to remove the seat and disconnect the yellow connector. Make sure you wait at least a minute before turning the car back on after its all put back together (this is per my dealer).

Wiring:

If you decide to order the entire harness, then skip this section. Otherwise, the information needed to create the two harnesses is below:

At a high level, we need to create two harnesses:
1. From the new switch to the existing connector.
2. From the existing connector to the new pump and valves.

It is very important that the connections between the two wires is soldered and is wrapped in heat shrink. Also make sure you label each pin, bushing, and harness so that you remember what they are for.

The existing connector is labeled on all three diagrams but is also noted by X11586 (in green)

I'm writing this DIY several months after the installation, so I don't recall the exact pin relationships.

Wiring Diagrams:

Existing Connector Inputs/Outputs (diagram label: X11586):

Side Bolster Diagram:

Driver Lumbar Support Diagram:

The side bolster diagram is what was in place in my vehicle and was utilizing the connector.

The open pins on the connector are for the missing lumbar support.

I tapped the existing side bolster switch for power and grounded the new lumbar switch under the seat. For power to the new valve, I tapped the power leading to the pump, per the diagram.

Trace the above diagrams from switch to connector and then to the pump and valve

Before you start soldering, make sure of the following:

The bushing/pins correspond to the switch, valve, or pump you are connecting them to.

Pins are inserted into bushings.

If you have any questions on the diagrams, just shoot me a PM.

Finished Harnesses:

--------

Installation

1. Remove the 2 clips on the bottom of the seat back by cutting them with wire cutters or just pulling down. There is a high risk that these clips will be wrecked, but if you're careful they can be reused.

Once the clips are removed, slide the back down a few inches and rotate it to the right. Once it has been rotated, it can be removed. If you try to remove it without rotating, the six clips can snap... so be careful.

2. Once the back of the seat is off, you'll see a white fabric, covering the existing valve for the side bolsters. There are four catches holding it in place. The two along the top need to be removed first; then it will slide down, out of the remaining two along the sides.

3. In various instructions I found, the pump is supposedly held in by two clips. In my case, it was zip tied. The valve was held in by the pressure of the tubing. Simply slide it to the right and it will fall off. Unclip the existing harness from the valve and cut the zip ties holding the pump in place. Remove the pump, tubing, and valve (can be removed as one piece, not whats in the picture).

4. The new pump and valves

5. Insert the new lordosis pad behind the wire mesh. It needs to be inserted sideways, and once it's in place, it can be rotated to fit.

6. Put the bottom foam tabs over the 3rd wire (from the bottom) and the top tabs over the 5th wire (from the bottom). Route the new tubing to the right, and out of the wire mesh.

7. The hole for the switch is already scored. I used a dremel with a small drill bit and punched several holes. I then switched to a sanding bit and slowly sanded down to the outer edge of the ring.

If you sand too quickly, the plastic will melt.

8. The new switch clips in from the back. Once you have it clipped in, make sure the buttons move in all directions without any resistance.

9. Connect the switch side of your new harness, and snake it through the seat following the existing cabling and connect it to the existing harness. From the existing harness, fish it up the right side of the seat (from the back), and make your connections to the pump and valve. Connect the existing harness to the side bolster pump (a wire fish comes in handy for this).

New Pump and Valves Installed:

Valves close up:

I went zip tie crazy, just to insure everything stays in place (notice all the green zip ties).

Test everything multiple times before you put it back together

10. Put the white fabric back in place.

11. Re-attach the seat back. Reverse the procedure above. Start at a 25 degree angle and rotate the seat cover so it's straight. This will engage the two clips on each side of the cover. You'll need to slide the cover upwards to engage the clips at the bottom and top.

This is my first DIY, please give me any suggestions you may have!

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