3LB/CAN Devices

VW MKIV FIS clusters can interface with OEM radios, navigation units and other devices to allow text and graphics to be displayed on the cluster. Non-CAN clusters (1Jx8xxx4x) can only receive text via the VW 3LB (3 Line Bus).

The 3LB consists of 3 wires:

Older clusters used a 20-pin red connector for 3LB.

CAN clusters (1Jx9xxx4x) can receive text via 3LB or the infotainment CAN bus. The CAN bus consists of 2 wires:

VW single-DIN radios are not connected to the cluster and thus cannot display station information on the cluster.

VW double-DIN radios are connected to the cluster via the CAN bus. The cluster uses the CAN bus to tell the radio when to turn on/off and when to illuminate the display. The radio uses the CAN bus to send station information to be displayed on the top 2 lines of the FIS display.

VW navigation units can display both text and graphics on the FIS display and can communicate to the cluster via 3LB or CAN, depending on the model of the navigation unit.

3rd party units such as FISBlocks, VFIZ, and FIS-Control use 3LB to display data on the cluster. I do not know of any that use CAN to communicate with a VW MKIV cluster.

The cluster can be programmed to accept text/graphics via 3LB or CAN communication, but not both. It can be tricky to get the cluster to switch from one communication method to the other, but the following methods should work:

Connect a 3LB Device

Perform the following steps in order:
  1. Remove any CAN-enabled radio or navigation system. You cannot have a CAN-enabled radio or navigation system connected to the cluster. Most VW factory double-DIN radios use CAN so you cannot use them if you have a 3LB device (such as FISBlocks) installed.
  2. If the first 2 digits of the cluster’s soft coding are less than 16, recode the cluster, adding 16 to the first 2 digits (e.g. if the old coding was 05230, change it to 21230).
  3. Recode the CAN gateway to the same value that it already is. This causes the CAN gateway to scan the CAN bus and discover any devices there. If the cluster had previously been communicating with a CAN-based radio, this will cause it to “forget” the radio, allowing it to communicate with a 3LB device.
  4. Disconnect power from the cluster and 3LB device for 30 seconds or so and then power them back up.

Connect a CAN Device

Perform the following steps in order:

  1. Install a CAN-enabled radio or navigation system. Remove anything connected to the cluster's 3LB. You cannot use both CAN and 3LB at the same time.
  2. If the first 2 digits of the cluster’s soft coding are greater than 16, recode the cluster, subtracting 16 from the first 2 digits (e.g. if the old coding was 21230, change it to 05230).
  3. Recode the CAN gateway to the same value that it already is. This causes the CAN gateway to scan the CAN bus and discover any devices there.
  4. Disconnect power from the cluster and CAN device for 30 seconds or so and then power them back up.