Where is the boot wiring in an estate?

[877]

I have the 2018 Octavia VRS estate mk3 2.0 184hp, with power boot option but I did not choose towbar wiring at order. 

 

I'm looking for a position in the boot where I can access the following wiring (in order of preference):

 

1) CAN-BUS for lighting

2) towbar modules (I did not purchase factory fit so might not be there)

3) Indicator/brake/reverse wiring

 

Any tips would be appreciated, it's for an electronics project I have in mind and I'm checking the feasibility.

 

Thanks

 

 

 

 

 

 

[SashaGrace]

What project do you want to undertake? The space for the towbar module is behind the boot side carpet on the left side of the car (nearside UK) and it will not be there unless the car has a towbar. The BCM is responsible for lighting signals so there isn’t CAN wiring there for that but there are many CAN connection points around the BCM behind the trim panel with the bonnet release, I can provide wiring colours/pin layout for the CAN connection. You can see the wiring for the light cluster when you remove it. It will also be grouped in with the wires behind the boot side carpet as so...

 

[877]

Hey Sasha thanks for that! The project I have in mind is to create a wireless number plate light board. It's more of a hobby thing, I know I could buy something but I like a little project.

 

First step of this is to feed the car signals (indicator L, indicator R, reverse and brake) into an esp32 arduino which would transmit the signals over bluetooth.

As I said the options are:

1) Read directly from can-bus - most elegant solution but may be difficult to 'sniff' the relevant commands, also might need wiring to front of car?

2) Utilise tow bar module - as you said certainly not going to be there

3) Tap into existing wiring from rear light units - using high resistance voltage dividers should not draw more than a few microamps which I hope would not be detected/throw up an error

 

There are no CAN connections in the boot area then it would seem? Any info you have would be useful, and if you could explain more what those wiring looms are for in your photo.

 

Cheers

Chris

 

 

Edited 18 February, 2020 by 877

[SashaGrace]

Interesting, please see below

 

 

If that’s unclear, the purple is for the power boot control unit, all of the white wires wrapped in cloth tape are for that (unfitted as that’s why I had this exposed for the photo), the red circle with the yellow wires is the left rear light. The yellow extension loom is a conversion loom for the FL tail lights. The blue circle shows the park sensor and right rear light signal loom that goes to the front with the power boot cables etc. The orange is the boot interior light circuit.

The CAN connections are below

 

 

You can connect to these circuits at various points. I recommend you make an account on ErWin, pay the €7 for an hour and download every diagram relating to this that you can.

 

You could get a towbar module and wire it in to the CAN system and make the connections to the BCM or you can manufacture something to emulate the signals as the BCM connections you will be making for lights will surely be the same? Either way, the BCM is responsible for these signals on the Octavia 3. If you were to connect to CAN, what would the car be looking to add to the gateway? Presumably it’ll be looking for the towbar module if you were to go down that route? 
 

An interesting project certainly.

[877]

Thanks again that's very helpful. I'm going to have a good look at this tomorrow when I'm back from work. I will gather some info for you to explain how to read the can-bus data.

Cheers

[SashaGrace]

No worries. The CAN Gateway on the MQB cars only has the 20 pin multi plug on it but the layout is the same.

[877]

@SashaGrace thanks again for the information, here is a link to the principle of reading the can-bus data:

https://www.instructables.com/id/CAN-Bus-Sniffing-and-Broadcasting-with-Arduino/

 

To get started testing it should work with a laptop and the following:

Arduino UNO

Can-bus shield

OBD cable

 

My application is only to read the can-bus signals, so there should be no need to purchase a towbar module, or emulate any signals. Hopefully the arduino code could be made to recognise the relevant signals (left, right, reverse, brakes) and send an output of some sort. Initially the outputs could be easily sent to a phone app such as Blynk, to confirm the signal are being read correctly. In the end solution they would be transmitted to another arduino in the remote trailer board, probably via bluetooth.

 

According to the linked can bus guide here and here, it looks like there are typically three can-bus networks  (drive/convenience/infotainment). It seems the lighting is on the convenience can-bus which runs at low speed 100kbps (orange/green & orange/brown wiring). So maybe I would need to connect to the J533 pin 5 & 15 to check this all out first.

 

I was kind of hoping that the convenience can-bus wiring ran into the boot somewhere, as it would be easier to connect everything there, and would ultimately be closer to the remote tailboard so communication would be better.

 

Also, I think all of this can be accessed via the normal obd2 port, in which case do all of the can-bus's terminate there somehow?

 

I'm going to do a bit more reading, any other help is much appreciated!

Chris

 

 

 

Edited 19 February, 2020 by 877

[SashaGrace]

That’s interesting, hope you can find a way to make it work. I had to add the power boot CAN connection to the drivers footwell which is the best place to splice on that circuit where it comes out of the drivers door. Positive is Pin 15, orange/green and Negative is Pin 5, orange/brown. The Bus Gateway is in the drivers footwell, not far from the steering column, everything terminates there.