Depinning Center control switch

[Darbshaw]

Does anyone know of an easy way to independently wire the switches for:
DSC, Sport, tire pressure system

I’m wanting to get these on their own to save some space of the controls that I have left. I really only need the DSC but the others may be beneficial to have just so I don’t have to deal with the tire pressure light on the dash to annoy me.

Ideally I’d like to just put these on their own style of button but I would lose the K-Bus wire and I’m not sure how important that is on a gutted car.

I tried to depin these from the center controls for the later model switch, but the controller doesn’t seem to want to work without all pins being present (except the tire pressure)

Ideally, wire these onto their own buttons that I can place outside of the oem housing
I can settle for just depinning the unnecessary parts and reducing the rats nest. This is for my track car, I’m just not going for a full reduced harness this year.

I hope I got my question across well. Thanks guys!

[George Hill]

So I understand, you want to loose the SZM and have JUST the DSC, Sport and RDC/TPM on their own three switches for a track car?

The DSC button goes to the (4) wire connector on the SZM and you can get just a DSC button as some cars didn't come with an SZM. Do you need the ability to turn DSC on/off? If you unplug the brake fluid level sensor then you with have DSC off with ABS still active and you don't need the switch either.

Do you use Sport on a track car, if so can you just code the DME to be Sport always on? And then you don't need the switch.

TPM is just to turn the light off in the dash? I would code it out and then you don't have the light or the switch, is that an option?

[Darbshaw]

So I understand, you want to loose the SZM and have JUST the DSC, Sport and RDC/TPM on their own three switches for a track car?

The DSC button goes to the (4) wire connector on the SZM and you can get just a DSC button as some cars didn't come with an SZM. Do you need the ability to turn DSC on/off? If you unplug the brake fluid level sensor then you with have DSC off with ABS still active and you don't need the switch either.

Do you use Sport on a track car, if so can you just code the DME to be Sport always on? And then you don't need the switch.

TPM is just to turn the light off in the dash? I would code it out and then you don't have the light or the switch, is that an option?

Thank you for the reply, that is spot on for what I'm looking for.


Ill look into decoding the the car to get rid of the tpm functionality. I think that's going to be the best option for me. No need keeping it around for just fun.
I think the same for the sport mode, it'll primarily be me driving it so I can just build the throttle curve to what I like and go with that.


As for going with a solo DSC switch, I saw a few of these on eBay. Do you know if it's possible to wire to just a momentary switch? Or is there some circuitry inside the button that is important to toggling DSC? I bought a momentary switch to try this.

Good to know about unplugging the fluid sensor. Thank you! This is my first run into anything serious wiring wise, so I appreciate your help


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[Darbshaw]

So it looks like fuse 12 for pin 22 was blown on X1869 that's what was causing my issue for the system to not work with the other parts depinned.
So as I stand I can use the large control switch with just the desired buttons.

The standalone DSC uses a different connector and I'm assuming a different pin out. I'm having issues finding this plug/pin out on TIS.

I'm not optimistic that I can use just a standard momentary switch to replace the DSC button. Unless fuse 12 is just required for the power to the center switch.

My guess is that the 6 pin plug uses all four from the 4 pin, plus fuse 12

[Darbshaw]

Found this here, for older Z3's but the plugs seem to be the same. Maybe I can just use a simple switch for this, button should be here tomorrow so I'll give it a whirl.

On a pre-facelift switch there are 6 pins on the switch however only 4 are used as follows:
Pin 6 - ASC switching signal
Pin 4 - Ground
Pin 2 - Lighting
Pin 5 - ASC power
When the switch is operated it routes power from pin 5 to pin 6

On a post-facelift switch there are 4 pins, all are used as follows:
Pin 4 - ASC switching signal
Pin 2 - Ground
Pin 3 - Lighting
Pin 1 - ASC power
When the switch is operated it routes power from pin 1 to pin 4

In order to get the later switch to work in an earlier car you just need to ensure that you move the sockets 1 at a time between the old and the new connectors i.e.

Pin 6 to Pin 4
Pin 4 to Pin 2
Pin 2 to Pin 3
Pin 5 to Pin 1

Source: https://www.bimmerforums.com/forum/s...SC-switch-swap

[Darbshaw]

Last one for the night I swear.

The DSC button was never designed to be used without the center switch. Even though pin 1 on the DSC connection is ran and fused the center switch cannot be used without power from pin 22 on X1869.

[heinzboehmer]

I'm not optimistic that I can use just a standard momentary switch to replace the DSC button. Unless fuse 12 is just required for the power to the center switch.

Looks like the DSC button output from the switch center is expected to always be high except when the button is pressed:


Should be easy replicate the functionality with a momentary switch and a pull up resistor. I'd probe the switch center with a multimeter first though, just to make sure the schematic above is accurate.

Edit: I think I'm reading BMW's wiring diagram correctly, but upon looking at it again, I'm less confident than I was before. Either way, the DSC button is going to be high when unpressed and low when pressed or low when unpressed and high when pressed. Should be easy to figure out the logic by giving the switch center Vcc and Gnd and then probing the output pin with the button pressed and unpressed. With that info, you can then decide whether to use a pull up or pull down resistor with your momentary switch.

[George Hill]

I'm confused as to what the goal is.

Are you trying to get rid of the SZM or have everything on its on switch?

Some Non-M's did not come with SZMs as such they just had a DSC button. That button can connect straight to the 4 pin connector at the SZM and then the SZM goes in the trash.

Solo DSC switch pn#

61316901592

https://www.google.com/search?q=6131...hrome&ie=UTF-8


Center console trim for single button:

https://www.google.com/search?q=51168205378&sourceid=chrome&ie=UTF-8

[Darbshaw]

Edit: I think I'm reading BMW's wiring diagram correctly, but upon looking at it again, I'm less confident than I was before. Either way, the DSC button is going to be high when unpressed and low when pressed or low when unpressed and high when pressed. Should be easy to figure out the logic by giving the switch center Vcc and Gnd and then probing the output pin with the button pressed and unpressed. With that info, you can then decide whether to use a pull up or pull down resistor with your momentary switch.

Excuse my ignorance here as my electrical knowledge is that of a third grader. I'll have to do some research into pull up or down resistors. First I've heard of these.

In the post that I linked a few before one of them tested that the DSC switch sends voltage out to the abs unit with pin 2. That or they confirmed continuity not voltage.

Is there any specific reason as to why use a pull resistor? What negatives would come of just straight wiring a momentary switch?


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[Darbshaw]

I'm confused as to what the goal is.

Are you trying to get rid of the SZM or have everything on its on switch?

Some Non-M's did not come with SZMs as such they just had a DSC button. That button can connect straight to the 4 pin connector at the SZM and then the SZM goes in the trash.

Solo DSC switch pn#

61316901592

https://www.google.com/search?q=6131...hrome&ie=UTF-8


Center console trim for single button:
https://www.google.com/search?q=5116...hrome&ie=UTF-8

Original plan was to have the buttons all on their own for packaging reasons. The car is gutted and I wanted a good way to pack the buttons I need together without having to fight the control switch bar.


Now I'm just trying to figure out the best way to wire the DSC button independently. It was quicker and more cost effective to order a generic momentary switch than to buy an oem single DSC button.

My problem was figuring out how to wire it because my real world experiences were not lining up with the diagrams


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[heinzboehmer]

Excuse my ignorance here as my electrical knowledge is that of a third grader. I'll have to do some research into pull up or down resistors. First I've heard of these.

In the post that I linked a few before one of them tested that the DSC switch sends voltage out to the abs unit with pin 2. That or they confirmed continuity not voltage.

Is there any specific reason as to why use a pull resistor? What negatives would come of just straight wiring a momentary switch?


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The purpose of a pull up/pull down resistor is to provide a steady reference voltage when the switch isn't being pressed. If this is omitted, then the voltage will be whatever it wants at the DSC input pin and might cause undefined behavior when the switch is open. There's a good amount of online resources that explain this in more depth (and eloquence) than me.

However, I'd probably just grab that switch that George linked and call it a day. Does what you want with zero messing around.

[Darbshaw]

The purpose of a pull up/pull down resistor is to provide a steady reference voltage when the switch isn't being pressed. If this is omitted, then the voltage will be whatever it wants at the DSC input pin and might cause undefined behavior when the switch is open. There's a good amount of online resources that explain this in more depth (and eloquence) than me.

However, I'd probably just grab that switch that George linked and call it a day. Does what you want with zero messing around.

I did some research last night and I think I have a decent understanding of the concept now.

I had the generic switch here and in hand, so I decided to attempt and wire it up.

Using the switch to complete the circuit between pins 1&2 allow the switch to work perfectly. The quick press works for MTrack and the hold works for full disable

Thank you for the information on the resistors. I will look into this if I start to get some one off issues or random triggers I'll look into this as a solution.
My assumption is that a pull down would be needed here. I wasn't able to get anything conclusive from probing the original switch.


Hindsight, if I could find a 4 pin dsc button for less than $20 I'd 100% go that route. I didn't know a 4 pin option existed, only the 6.
Since this is all going to attach to a homemade panel and the car is gutted. OEM looks isn't important anymore.


Thank you both for your inputs and feedback