How to get raw CAN traffic from a car with the help of OBD2?

0
votes

I made a device with an with an OBD2 cable , soldered its CAN-H and CAN-L lines to a USB-CAN interface called USBtin (https://www.fischl.de/usbtin/). When I tried mode 1 of OBD2, I received just one reply for one query like:

  slcan0       7DF   [8]  02 01 0C CC CC CC CC CC
  slcan0       7DF   [8]  02 01 0B CC CC CC CC CC
  slcan0       7E8   [8]  04 41 0C 0C 06 00 00 00
  slcan0  17F00010   [8]  20 10 00 00 00 00 00 00
  slcan0  17F00010   [8]  20 10 00 00 00 00 00 00
  slcan0  17F00010   [8]  20 10 00 00 00 00 00 00
  slcan0       7DF   [8]  02 01 0C CC CC CC CC CC
  slcan0       7DF   [8]  02 01 0B CC CC CC CC CC
  slcan0       7E8   [8]  04 41 0C 0C 0A 00 00 00
  slcan0  17F00010   [8]  20 10 00 00 00 00 00 00
  slcan0  17F00010   [8]  20 10 00 00 00 00 00 00
  slcan0  17F00010   [8]  20 10 00 00 00 00 00 00
  slcan0       7DF   [8]  02 01 0C CC CC CC CC CC
  slcan0       7DF   [8]  02 01 0B CC CC CC CC CC
  slcan0       7E8   [8]  04 41 0C 0C 0C 00 00 00

  1. Is there a OBD mode or a PID which will keep on sending me the latest values until I disconnect from the OBD?

  2. Is there a mode or PID with which I can capture proper raw CAN traffic like below?

 slcan0  220   [8]  01 04 00 00 0A 00 D9 0D
 slcan0  316   [8]  45 42 80 11 42 3A 01 00
 slcan0  329   [8]  0B 7C 80 08 00 26 FF 0C
 slcan0  18F   [8]  00 00 00 00 00 59 00 00
 slcan0  002   [8]  00 00 00 00 00 04 07 74
 slcan0  130   [8]  AC 7B 00 FF E4 7F 07 38
 slcan0  140   [8]  00 00 00 00 06 20 17 E4
 slcan0  2B0   [5]  27 14 00 07 16
 slcan0  153   [8]  00 00 00 FF 00 FF 70 6E

I would appreciate any help!

1
can-busobd-ii
Don't forget to solder signal ground as well. Your PC will have a wildly different ground potential compared to your car. – Lundin

1 Answers

0
votes

  1. No. OBD2 is based on request/response schemes. If you want regular value updates, you need to ask regularly.

  2. For sure. If you turn off all message filters (should actually be the default with SocketCAN) and read continuously, you should pick up all the traffic – provided you have a direct connection to the ECU. Newer cars tend to connect a gateway ECU behind the OBD2 socket in order to filter certain functionality.