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Can't see bus traffic using MAX on an Audi Q7

A few years ago, I tried OBD II on several (European) cars using NI ADCS with LabVIEW. All worked succesful, except those from VAG. I contacted someone at VAG who told me that OBD on CAN isn't wired in cars sold in Europe. Only cars exported to the US have a special OBD CAN gateway ECU that opens the OBD II CAN messages (and only those) to the OBD II connector as required by US legislation. I don't fully understand what you mean by 'enhanced Message IDs'... but if you mean just the 'normal' (non OBD II) CAN traffic, then no, you won't see it on the OBD II connector as the gateway wouldn't pass that traffic to the OBD II connector.

Message 11 of 23
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@sfrosty wrote:

@Gibson wrote:
If using Busmonitor in MAX you need to run your ADCS application on the 2nd CAN port

If you did check your termination

What is ADCS?


Oh, the LabVIEW Automotive Diagnostic Command Set.

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Message 12 of 23
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Yes are using this?
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Message 13 of 23
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@Gibson wrote:
Yes are using this?

Yes I am using the ADCS! The application I created using the ADCS works great and all information from the bus is displayed normally! However, when I quit the ADCS application, open MAX and select the NI-CAN BusMonitor, there is no bus traffic displayed.

The information that is displayed using the ADCS VIs is what I refer to as the Legislative messages mandated by the US government.

The information that is displayed using MAX and the NI-CAN BusMonitor is what I refer to as the Proprietary or Enhanced messages, available only to the OEMs without having special permission to identify the message sets.

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Message 14 of 23
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@Ceule wrote:

A few years ago, I tried OBD II on several (European) cars using NI ADCS with LabVIEW. All worked succesful, except those from VAG. I contacted someone at VAG who told me that OBD on CAN isn't wired in cars sold in Europe. Only cars exported to the US have a special OBD CAN gateway ECU that opens the OBD II CAN messages (and only those) to the OBD II connector as required by US legislation. I don't fully understand what you mean by 'enhanced Message IDs'... but if you mean just the 'normal' (non OBD II) CAN traffic, then no, you won't see it on the OBD II connector as the gateway wouldn't pass that traffic to the OBD II connector.


 

 

Please refer to message Post 14. Thank You!

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Message 15 of 23
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Let me ask this question in another way. If I can monitor the signals utilizing CAN and LabVIEW NI ACDS functions on the Audi Q7 Quatro, should I also be able to monitor bus traffic utilizing the Bus Monitor function in MAX? Or are these signals completely independent of each other; while one type of signal transmission may be available and the other not available? Smiley Frustrated Thank You!

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Message 16 of 23
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I assume on your OBD connector there is no CAN communication taking place beside Diagnostic Communication.

That means if you just connect the BusMonitor to the OBD connector there is no CAN traffic at all.

The Diagnostic Protocol is a handshake which is initiated by the Diagnostic Master (LabVIEW Application using ADCS). As long as your LabVIEW app does not execute any Diagnostic Service there is no communcation on the network.

 

If you have a 2 port CAN board you can connect port 1 and 2 to the same network with the ECU. e.g. on port 1 launch MAX NICAN BusMonitor and on Port 2 your ADCS application. As soon as a Diagnostic Service is executed by the ADCS app you should see the tranmited frames from ADCS as well as the CAN frame responses from the ECU.

 

Hope this helps

Message 17 of 23
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@Gibson wrote:

I assume on your OBD connector there is no CAN communication taking place beside Diagnostic Communication.

That means if you just connect the BusMonitor to the OBD connector there is no CAN traffic at all.

The Diagnostic Protocol is a handshake which is initiated by the Diagnostic Master (LabVIEW Application using ADCS). As long as your LabVIEW app does not execute any Diagnostic Service there is no communication on the network.

 

If you have a 2 port CAN board you can connect port 1 and 2 to the same network with the ECU. e.g. on port 1 launch MAX NICAN BusMonitor and on Port 2 your ADCS application. As soon as a Diagnostic Service is executed by the ADCS app you should see the transmitted frames from ADCS as well as the CAN frame responses from the ECU.

 

Hope this helps


Thanks for your quick response! I don't need to monitor both at the same time. I only need to monitor individually. Here's the scenario: I plug into the OBD connector, launch the ADCS application and all signals are displayed using my ADCS LabVIEW application. I then exit out of my ADCS LabVIEW application, open MAX, open the Bus Monitor, and no bus traffic is displayed. Why is that? Thanks!

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Message 18 of 23
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what traffic do you expect???

 

again as I said above: as soon as you stop your Diagnostic App there is no CAN traffic any more executed from either Master (LabVIEW/ADCS) nor Slave (gateway ECU on OBD)

for me this sounds like expected behaviour that there is no traffic after you stop the Diagnostic service.

Message 19 of 23
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@Gibson wrote:

what traffic do you expect???

 

again as I said above: as soon as you stop your Diagnostic App there is no CAN traffic any more executed from either Master (LabVIEW/ADCS) nor Slave (gateway ECU on OBD)

for me this sounds like expected behaviour that there is no traffic after you stop the Diagnostic service.


Oh, I see, what you are saying is that the ADCS app is initiating the BUS traffic. So, if I utilize the other port I would than also see the bus traffic using MAX. Correct?

Here's what I normally see on any other vehicle (at least 20 other vehicles) I have tested: I plug into the OBD connector, open MAX (only), no LabVIEW ADCS app, and I see all the bus traffic. But on this vehicle, when I only have the MAX Bus Monitor running, I see no Bus traffic.

 

This is what I expect: Connect to the OBD connector, open MAX, click on the Bus Monitor function, and all bus traffic is displayed. Smiley Indifferent

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Message 20 of 23
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