Description
Simplify your JB4 installation on compatible BMW G Chassis vehicles and the Toyota GR Supra with the JB4 ECU Direct CANbus Harness. This plug-and-play harness connects the JB4 directly to the vehicle’s CANbus at the ECU, eliminating the need to route a CAN/OBDII cable through the firewall and into the passenger compartment.
By connecting directly at the ECU, this harness provides a cleaner, faster, and easier JB4 installation without requiring wiring to be routed through the firewall or into the passenger compartment to access the OBDII port under the dash.
The Direct CANbus Harness also enables passive CANbus mode, allowing the JB4 to use read-only CANbus channels for basic tuning while keeping the vehicle’s OBDII port fully available for data logging through MHD or other compatible scan tools during full-throttle runs.
Features
- Direct CANbus connection at the ECU
- Eliminates the need to route wiring into the passenger compartment
- Cleaner and more professional JB4 installation
- Significantly reduces installation time and installation hassle
- Plug-and-play design
- Designed for G Series BMW B58 and S58 applications
- Compatible with B58-powered Toyota GR Supra applications
- Higher CANbus sample rate through direct connection to PTCAN
- Allows passive CANbus operation when supported by compatible JB4 or JB4PRO firmware and settings
- Keeps the OBDII port available for logging with MHD or other scan tools when operating in passive mode
Important Notes
- Requires compatible JB4 or JB4PRO firmware and settings to enable the Direct CANbus Harness.
- For JB4PRO B58/S58 systems, turn on Option 11 to enable the harness.
- Turn on Option 12 to run the JB4PRO in passive mode only.
- In passive mode, certain CANbus channels, including AFR and timing corrections, are not available.
- Passive mode would normally only be used when the vehicle’s OBDII port is otherwise occupied.
- Not compatible with 2025+ Gen3 B48/B58 platforms.
Fitment
BMW G Series – B58 Applications
- BMW G Series B58 vehicles
- BMW G Series B58 applications compatible with the JB4 Direct CANbus Harness
- Requires a compatible JB4 or JB4PRO system and firmware
BMW G Series – S58 Applications
- BMW G Series S58 vehicles
- BMW G Series S58 applications compatible with the JB4 Direct CANbus Harness
- Requires a compatible JB4PRO system and firmware
Toyota GR Supra – B58 Applications
- Toyota GR Supra B58 applications compatible with the JB4 Direct CANbus Harness
- Requires a compatible JB4 or JB4PRO system and firmware
Platform Exclusion
- Not compatible with 2025+ Gen3 B48/B58 platforms
Installation and Operation
The JB4 ECU Direct CANbus Harness is designed to simplify installation by connecting the JB4 directly to the vehicle’s CANbus at the ECU. This eliminates the conventional process of routing the CAN/OBDII cable through the firewall and into the passenger compartment.
For compatible JB4PRO B58/S58 systems, Option 11 enables the Direct CANbus Harness, while Option 12 allows the JB4PRO to operate in passive CANbus mode. Passive mode uses read-only CANbus channels for basic tuning and allows the OBDII port to remain available for logging with MHD or another scan tool. Because passive mode does not provide access to certain channels such as AFR and timing corrections, it is generally intended for situations where the OBDII port is occupied.
