Possible cause of fault

• Diagnosis distribution line: short circuit to ground/ B+ or open circuit
• Optical waveguide damaged
• Optical waveguide broken
• Optical waveguide kinked
• The recipient MOST control module is faulty
• PCM2 faulty

The diagnosis distribution line is connected to the following MOST control modules:

• PCM2 as of model year 2003 
• PCM2 gateway 
• PCM2 MMI 
• PCM2 navigation (optional) 
• The diagnosis distribution line and the MOST optical waveguide are connected to the following control modules: 
• External amplifier (Harman or BOSE) (optional) 
• CD changer (optional) 
• Telephone/telematics (optional) 

Fig 1: Block Diagram Of Network Components

Courtesy of PORSCHE OF NORTH AMERICA, INC.