MOST Bus Diagnosis

The audio and visual system in this vehicle has a MOST communication network that is used for communicating audio, video, and control signals. This network consists of the gateway unit (gauge control module) and node units (tuner unit, stereo amplifier, and infotainment control unit), and the MOST circuit of each unit consist of MOST_ECL lines, MOST TX+/MOST RX+ lines, MOST TX-/MOST RX- lines. and power and ground lines. The MOST bus forms a ring topology between each MOST connected unit. If the MOST network fails, the audio and visual system will be inoperative.

If an abnormal symptom appears in the audio and visual system, it may be intermittent failure of MOST network. If the center display unit displays ordinary screen, do the System Diagnostic Mode, and use the Shutdown Reason to check the MOST bus condition .

If the audio and visual system does not work, or does not work properly, check these items:

• Do the gauge control module Self-Diagnostic Function to check communication lines (B-CAN and F-CAN) condition .
• Do the ECL test (refer to How to Check MOST Bus Condition).