J533 Sniffing Cable

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Volkswagen Group OBDII Port CAN-Bus Explanation

The Volkswagen Group OBDII port delivers only a CAN Diagnose high/low signal. Usually Pin 6 is CAN-High and Pin 14 is CAN-Low. That means that you can only access the CAN ECU (Electronic Control Unit) e. g. ACC (Adaptive Cruise Control) via a Diagnose tool like VCDS. The OBDII CAN-Diagnose pins are connected to the J533 CAN Gateway (a. k. a. Data Bus Diagnostic Interface). This interface is responsible for communication between the different CAN-Bus Networks. These are:

  • Drive train CAN Bus (high-speed)at 500 kbps with almost real time requirements (can0)
  • Convenience CAN Bus (low-speed) at 100 kbps with low time requirements (can1)
  • Infotainment CAN Bus (low-speed) at 100 kbps with low time requirements (can2)
  • Those are the three main Networks. There are others too.

J533 Gateway is responsible for communication between all those CAN Networks. You can't pair "Drive" and "Convenience" CAN Bus cables together because of different Bus speeds. That's why J533 is needed as a Gateway. For sure there are also other applications.

To get directly connected to the CAN-Bus of your choice, you have to tie up directly on the corresponding cable. You could build your own sniffing cable. You need following things:

  • Connector Housing from J533 Unit. Here comes the car harness in (Link: https://goo.gl/QojWYR) (Mouser P/N 571-966871-1)
    • Another possibility is to buy a used J533 Gateway from eBay and desolder the Connector Housing. P/N are e. g. 1K0907530G, 3C0907530C, 3C0907951A, there a much more.
  • Connector to J533 Unit (Link: https://goo.gl/7eAExf) (Mouser P/N 571-1534102-1)
  • Terminal for Connector (Link: https://goo.gl/MKPEks) (Mouser P/N 571-928999-1-CT)
    • OE P/N: 8E0972420C can also be without "C". You can find cut off connectors with cable on it. So you don't have to buy cables and pins and crimp it.
  • For Panda sniffing connection (https://goo.gl/cajg5p), (https://goo.gl/6gg91j), (https://goo.gl/dVyNzL)
  • For cabel you will need 0.5 mm2 for power and 0,35 mm2 for CAN connections.

Sniffing Adapter Connection Schema (only for 20 pin J533)

Car Harness --> Connector Housing from J533 --> Cables to Connector and to OBDII Port for Panda --> Connector --> J533 Unit

J533 Sniffing Cable is working like a charm. Be sure to plug it completely in. First time it wasn't so car didn't start up! Be also sure to disconnect car battery for safety reasons before you plug out the cable from J533 Gateway.

Let's start. You have to solder a bridge for keeping up the old connection to the J533 Gateway. When building the bridge cable you have to connect each Pin 1:1. E. g. Pin 1 to Pin 1, Pin 20 to Pin 20. For connecting Panda the connection is being splitted from new connector housing which connects to car harness. There you have to connect the OBDII connector like in this simple

This schema is for Audi A3 8P 2006 but should fit the most Volkswagen Group cars. Just google to find the right pinout for your car. Check what connector housing your J533 has and look at the car harness connector. You can find J533 under the steering wheel on the top right side. It's mounted from the front with two clips. Sometimes it can be also directly behind the steering wheel. Just push them together to release them. To get access unter the steering wheel you have to remove the cover. There is usually one screw on the left side where all fuses are and two/three screws at the foot area, at the end of the cover (Torx screws). To release the light switch push the rotary knob in and turn it left, this will release it from the cover. You can pull it easily out.

Set correct Busspeed for Sniffing

If you have connected your three buses like above then you have to set the correct speeds. Otherwise you won't get can data on bus 1 and 2.

  • can0 = 500 kbps
  • can1 = 100 kbps
  • can2 = 100 kbps

Python commands:

  • can0 can be left at default value of 500 kbps
  • panda.set_can_speed_kbps(1, 100)
  • panda.set_can_speed_kbps(2, 100)