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Introduction

If you don't have LKAS (lane keeping assist/lane departure warning) or want to replace your ACC with OP, then you need to interface with your car at the J533 CAN Gateway under the steering wheel and above the pedals. J533 is the standard connection for all VAG cars which have the necessary gateway. The role of the Gateway (also known J533) is the exchange of data between the CAN databus systems ('powertrain CAN databus,' 'convenience CAN databus' and 'infotainment CAN databus') and the conversion of diagnostic data from CAN databus systems. This is a central point where openpilot can intercept data to understand the car's state, and manipulate and insert data to impersonate the lane departure warning system to provide lateral control.

J533 Gateway location

Lay on your back in the driver's footwell with a torch. Get as close to the firewall as possible. Look up. You will see a usually red and sometimes black connector. This is the J533 connector. It is plugged into the J533 CAN gateway. In some cars it's necessary to remove some stuff which is in the way, but often it can be directly accessed. If you are unsure, lay down your phone under the pedals in the middle of the footwell as far back as the flat are goes, point some light upwards and take a picture directly upwards. Post that picture in the #volkswagen-audi-skoda channel of the comma.ai discord.

VW Transporter / California J533 gateway location

On Volkswagen transporter, the gateway is behind the clocks of the instrument panel. Here is a video on how to remove it.

Caution: This picture shows the RJ45 plug disconnected. It needs to be plugged into the relay!

Installation

The j533 harness has everything necessary for the connection to the car integrated. There's NO need to access the LKAS camera or OBD2 port. For this purpose, the J533 harness has 4 Plugs:

2 x J533 plugs, male and female, which go between the gateway and the j533 plug of your car. Make sure to really press down the latch when removing the plug.

1 x white Molex connector which plugs into the relay (small black box)

1 x Rj45 connector which HAS to be plugged into the other side of the relay

It should look like this: To connect the relay to the C2/C3, you plug the long USB-C cable into the relay, route it along the A pillar to the headliner while making sure to stay behind the curtain airbag, and use the C to C coupler to connect to the straight plug of the smaller USB-C cable. The angled part of that cable goes into the C3. The long USB-C cable and the coupler are only included if you order a C3 with J533 harness. You can also provide your own cable. Make sure it is at least USB 3.1 gen2. 2 meters are just enough on a Golf. For a C3 you need an angled cable like the original one.

Technical Information

A source of some confusion is which direction data flows. In summary, the critical connection is for openpilot to intercept pins 7/17 of the J533 connector. The comma relay 'man-in-the-middles' the flow of data down the VW "extended CAN bus" (7/17 on the J533 connector). It's easy to wire it the wrong way around.

Data from pins 7/17 comes into CAN2 of the black panda from the socket end of the Aliexpress harness, gets manipulated by openpilot to add steering commands, and then is sent out CAN0 of the black panda to the J533 Gateway via the red plug of the Aliexpress harness. CAN0 and CAN2 are electrically connected together when the relay is operating in passthrough mode. So CAN0 should be connected to the red plug and CAN2 should be connected to the black socket.

Connector Gender

There is often confusion between whether connectors are referred to by the housing gender or the pin gender. Throughout this document connectors are referred to by pin gender, thus the RED J533 connector, despite being a 'plug' is a FEMALE connector because the individual contacts are female sockets

J533 pinout for MQB Vehicles

J533 wiring diagram for White/grey panda [EOL, only for openpilot 0.7.9 and below!]

Note: "panda Female" is shown when looking at the back of the connector. To avoid confusion ensure the pin numbers on the connector match the pin numbers written on the panda itself.

Shopping list for white/grey panda harness

1. Gateway Extension Adapter
2. OBD Female Connector w/ Wires | check eBay/Aliexpress
3. 60 ohm Resistor (5w or less)
4. Cloth electrical harness tape

J533 wiring diagram for comma two/black panda (Requires comma power and comma relay!)

comma two/black panda J533 harness with elimination of comma power (Requires comma relay!)

Combined comma two/black panda & White/grey panda J533 harness together

Shopping list for comma two/black panda harnesses

1. Gateway Extension Adapter
2. MQB Development Harness
3. Cloth electrical harness tape
4. Electrical connectors (butt splices if you're brave or DSUB pins/sockets if you are non-committal)