Audi A3 8P: Sending ignition signal via CAN bus

Hello,

My first contribution here; I've always been a silent reader until now.

Regarding my issue.

I'm using a custom-built car in motorsports, incorporating Audi A3 8P technology. The following CAN bus components are installed. Engine control unit, DSG mechatronics, steering column control unit, and the gateway – all of these are also working.

"Now, we also wanted to install the original speedometer. However, since the speedometer doesn't have terminal 15 (ignition power), it's currently not working. I've discovered that when the ignition is turned on, the ignition switch, which is connected to the steering column control unit, sends a command via CAN to the body control module. The body control module then sends a command to the speedometer. If I set it up like that, it would work, but I don't want to also install the body control module and the ignition switch just to power the speedometer." "In my setup, the ignition is switched on in a classic way using a switch and a relay, because all the other installed components still have the original terminal 15 and don't require CAN communication."


The question now is, is there a simple way to send the ignition signal to the CAN bus? Does anyone know which address I should send something to?

I've done some reading about the CAN bus, but I haven't actually worked with it yet. I'm also going to order the RKS-CAN interface. From what I've read, you can already use it to send test messages.

Best regards, Marco.

I was hoping to spark more discussion here, as this topic seems to come up frequently, but it never really leads to anyone providing a solution.

I'll try to post here what I find, so that maybe someone else can help.

Today, I've already set everything up and wired it so that the speedometer works with original components.

We can proceed once the ordered interface arrives.

Best regards, Marco.

Hello,

"Please search for 'Terminal 15'; it should have the CAN ID 0x3c0." There are many topics related to this.

Best regards, Rainer.

Hello Rainer,

Yes, I've found quite a few things already.

I saw that Interface is on the way. Then it's on to the next thing. I'm looking forward to it.

Best regards, Marco.

The interface arrived today.

0x3c0 is not present on my bus.

"The following applies when the ignition is switched on."

Hello,

Please provide the exact details of your vehicle.
If you have the opportunity, perform a VCDS autoscan.

Best regards, Rainer.

Pin 15, for example, corresponds to CAN ID 0x572, data byte 0 (D0 in the screenshot), bit 0 (0x01).

I don't have VCDS; I use cdp+ with the Delphi DS150E.

The test setup consists of components from an Audi A3 8P manufactured in 2005, with VIN WAUZZZ8P85A092962.

Speedometer, body control module, gateway, and steering column electronics.

It's not possible.

Hello,

Too bad. I would now record the CAN traffic on the vehicle for a few seconds.
Then, play back the recorded data on the test setup and see what happens.

If successful, you can then remove CAN IDs one by one until you identify the one that produces the desired effect.

Best regards, Rainer.

Now I understand the best way to find it.

So far, it's already working with minimal components.

Are the two CAN IDs shown in the previous screenshot the ones that generate a positive "terminal 15"?

What I also noticed is that the value 0x05 appears with 0x572 in your test setup, correct?
That message essentially indicates that terminal 15 is already present.

Perhaps the two messages are something else that requires additional information.

Best regards, Rainer.

Hi,

Yes, those two components appear in the test setup: the ignition switch, the steering column control unit, and the vehicle network control unit. I saved the entire list, minimized the test setup to only include the speedometer and gateway, imported the saved list, and then deleted IDs until it was no longer possible.

0x531 byte 1 controls the illumination of the speedometer.
0x575 byte 1: ignition switch position, 07: ignition on.

It took a while longer for me to figure out that I needed to send periodic signals for the speedometer to stay on.

Unfortunately, I no longer have access to the complete Audi system, which means I can't read all the IDs. Therefore, I can only obtain information about other data from other control units by searching online and through testing.

But I'm already happy that I've grasped this much, being a complete CAN novice.

You must have accumulated huge lists of ideas over the years, right? Are you taking them out?

Best regards, Marco.

Hoerli wrote:

You must have accumulated huge lists of IDs over the years, right?

Most of the information is documented here in the forum and scattered throughout various control unit descriptions.

It's definitely worth searching here.

Hoerli wrote:

Hello, Yes, those two components appear in the test setup: the ignition switch, the steering column control unit, and the vehicle network control unit. I saved the entire list, minimized the test setup to only include the speedometer and gateway, imported the saved list, and then deleted IDs until it was no longer possible. 0x531 byte 1 controls the illumination of the speedometer. 0x575 byte 1: ignition switch position, 07: ignition on. It took a while longer for me to figure out that I needed to send periodic signals for the speedometer to stay on. Unfortunately, I no longer have access to the complete Audi system, which means I can't read all the IDs. Therefore, I can only obtain information about other data from other control units by searching online and through testing. But I'm already happy that I've grasped this much, being a complete CAN novice. You must have accumulated huge lists of ideas over the years, right? Are you taking them out? Greetings Marco

Hello Marco,

You are correct about the ignition switch being at position 1 with 0x575 bytes. However, the ignition signal should actually be 0x2c3 (1 byte).

"Yes, I've read before that 0x2c3 is the ignition power signal, but apparently it's not for the speedometer. When I send that address, nothing happens with the speedometer. So, it seems to depend on the position of the ignition switch." Whatever the reason.