Troubleshooting The I/K Bus: Notes

The failure of communication on the I/K bus can be caused by several sources:

• Failure of the bus cable.
• Failure of one of the control units attached to the bus.
• Failure of the voltage supply to individual modules.
• Interference in the bus cables.

The I/K bus is active when KL R is switched on, it remains active until 60 seconds after the last message. If the key is switched off (KL30) the bus may be activated for a time by individual users via a "wake-up" message.

Unlike the CAN bus where each control unit (subscriber) provides voltage for communication, the I/K-busses use only determined Master  or Stand-by Controllers  to supply B⁺ for communication. The voltage level on the I/K bus must be above 7V. The nominal value should be close to the system voltage of the vehicle.

Just like the CAN bus, the fact that voltage is present does not mean that the bus is fault free, it just means that the voltage level is sufficient to support communication.

Control units that provide operating voltage to the I/K bus are: