Golf IV Engine CAN Bus System

Hello everyone,

I just logged some data from the engine control unit (ECU) on my Volkswagen Golf IV.

Help :)

Best regards,
Sven.

Okay, here are some more updates. I was able to associate the following IDs:

0C2 - Rotary angle/rate sensor for ESP (Electronic Stability Program).
280 - Motorsteuergerät. Byte 3 = Speed.
1A0 - ABS (possibly more than one ID?)


Regards,
Sven.

Hello,

I figured this out.

320 - Combination instrument. Byte 3 & 0x7f = fuel [liters], bit 7 = low fuel warning.
420 - Combination instrument.
byte 1 = External temperature, displayed (with delay), temperature = (value - 100) / 2.
byte 2 = External temperature, measured; temperature = (value - 100) / 2.
byte 4 = coolant temperature, calculated as: CLT = (value - 64) * 0.75.

280 - Engine Control Unit (ECU)
byte 2 = RPM * 4, L.
byte 3 = RPM * 4, High byte.

Hi,

'Where can I find the CAN bus connector on a Volkswagen Golf IV?'
'Is there also a comfort CAN bus? Where can I find it? Does anyone have any information about it?'

You're welcome.

I'm sorry, but I don't have access to that information. Perhaps you could try searching online or consulting with an expert in the field.

'In my GOLF IV, I have the Navigator head unit. According to the wiring diagram, it should support CAN bus, but it's not actually connected in the car! There are no wires plugged into the CAN bus pins on the connector.'

The radio broadcasts can be received at a data rate of 100 kbps.

'Thank you, Paolo.'

Hi,
Have you found the oil temperature on the CAN bus yet?

Regards,
Markus.

Here's another question: Does anyone have information about the power consumption signal? Is it also transmitted via CAN? If so, what is the ID?
I want to install an aftermarket CAN speedometer in my car, but unfortunately the fuel consumption display isn't working. I want to check if, for example, the relevant IDs are being transmitted.

Best regards.
Markus.

Markus,
The consumption signal is sent as ID 480, byte 3. The value (of the 3rd byte) and the time interval between messages together determine the displayed fuel consumption.

My experiment showed this:
2ms * 254 1/1.8
1ms * 254 3.7/2.8
1ms * 128 6.5 / 7.4
1ms * 25 32.3 / 33.2
1ms * 12 64.5 / 65.4

Here's a log from my motorcycle.

ID | DLC Data | Period Count | Comment
--- | --- | --- | ---
(Values would go here)
1A0 8 00 00 00 00 FE FE 00 00 6 3757
280 8 49 00 00 00 00 FA 36 00 19 1327
288 8 4D 42 10 00 00 5F 00 00 19 1326
380 2 00 44 19 1326
4A0 8 00 00 00 00 00 00 00 00 6 3757
5A0 5 00 00 00 5B B6 6 3710


It looks rather weak compared to Svens's code, unfortunately.

Currently, only the engine control unit (ECU) and ABS are connected to this bus.
So, the ID codes from the dashboard, specifically for the airbag and ESP systems, are disappearing.

@xyr
Can you explain that to me with an example?

Unfortunately, I'm still missing the IDs for the glow plug lamp and the fuel pump relay. Is the oil pressure still being sent to the speedometer via an analog signal?

@rathma

If you send a message every 2 milliseconds with 254 as byte 3, the device shows a flow rate of 1-1.8 liters per hour. If you send the same message every 1 millisecond, the device shows a flow rate of 2.8-3.7 liters per hour. And so on.

Okay, I understand. However, I find it hard to believe that there's such precise timing involved with the bus, as these types of messages can easily be delayed.

Does anyone know how the timing of an analog signal is determined?

Best regards.
Markus.

Hi,
What Sven wrote about the engine temperatures is not correct, at least for a ME 7.5 system.
There, the water temperature is transmitted from another location, and the conversion is as follows:

The byte value at decimal -100 represents the current water temperature.

Best regards, Flo.

Okay, I understand. However, I can hardly imagine that there is such precise timing on the bus, as these messages can easily be delayed.

Does anyone know how the timing of an analog signal is determined?

Best regards.
markus

The bus system has a very precise timing mechanism because adhering to cycle times is fundamental, for example, for error detection. Especially with a speed of 500k, significant bandwidths are possible even with the relatively short data packets. However, the method described above still contains a fundamental flaw in its underlying logic!

Best regards, Mike.

But I still can't imagine that a certain value is being transmitted through the timing signal.

However, the above method is still based on a fundamental flaw in thinking!


My words!