Checking Cable And Component

If the result of the ring break diagnosis is POOR it indicates that the infotainment module (ICM) receives signals on the MOST network but cannot decode them because the light strength is too weak or the signals are distorted.

If the result of the ring break diagnosis is OK it indicates that the fault is intermittent.

Fault tracing with ring break diagnosis presupposes that the fault is permanent or active while the test is running, i. e. when the system is powered up after a period without power.

HINT: If diagnostic trouble code ICM-DC01 is generated intermittently, obtain a ring break diagnosis status reading in Vehicle Communication frozen values. 

HINT: Note that the AM/FM tuner module (AFM) and traffic message module (TMC) do not normally take part in a ring break diagnosis if the fuse is removed. This means that a break position is displaced two steps rearwards in the MOST network. 

HINT: On a fully equipped vehicle where the break position is 5, the fault could be due to: 

• Multimedia module (MMM).
• The fiber optic cable between the multimedia module (MMM) and AM/FM tuner module (AFM).
• AM/FM tuner module (AFM).
• The fiber optic cable between the AM/FM tuner module (AFM) and traffic message module (TMC).
• Traffic message module (TMC).
• The fiber optic cable between the traffic message module (TMC) and the audio control module (AUD).

Bypass the control modules on the MOST network one at a time to check network communication. Proceed as follows:

• Ignition off
• Unplug the MOST connector from the relevant control module.
• Connect the MOST cable to special tool see 9512867 .
• Ignition on
• Activate the infotainment system.
• Check that MOST network communication is in working order. Do this by obtaining a status reading of the MOST locked parameter for at least 30 seconds. This parameter shows whether the MOST network is closed and communication possible.

If MOST network communication is stable when a control module is disconnected, check the power supply and ground connection of the control module for an intermittent fault. If no fault is found, try changing individual components.

Click on the VCT2000 symbol to obtain a MOST network status reading.

• Continue 

  Refer to VERIFICATION 

Select the control module to check according to the list.

1. Media player module (MPM)

Refer to CHECKING CABLE AND COMPONENT 

2. Phone module (PHM)

Refer to CHECKING CABLE AND COMPONENT PHM 

3. Subwoofer module (SUB)

Refer to CHECKING CABLE AND COMPONENT SUB 

4. Global positioning system module (GPS)

Refer to CHECKING CABLE AND COMPONENT GPS 

5. Integrated audio module (IAM)

Refer to CHECKING CABLE AND COMPONENT 

Select the control module to check according to the list. 

1. Audio module (AUD)

Refer to CHECKING CABLE AND COMPONENT AUD 

2. Traffic message module (TMC)

Refer to CHECKING CABLE AND COMPONENT TMC 

3. AM/FM tuner module (AFM)

Refer to CHECKING CABLE AND COMPONENT AFM 

4. Multimedia module (MMM)

Refer to CHECKING CABLE AND COMPONENT 

5. Infotainment control module (ICM)

Refer to CHECKING CABLE AND COMPONENT 

Checking fuses 

Check that the fuse for the function in question is intact.

Replace the fuse if it is damaged.

Checking the cause of the fault 

Check the cause of the fault as follows:

1. Ignition off
2. Unplug the MOST connector from the media player module (MPM).
3. Connect the MOST cable to special tool see 9512867 .
4. Ignition on
5. Activate the infotainment system.
6. Check that MOST network communication is in working order. Do this by obtaining a status reading of the MOST locked parameter for at least 30 seconds. This parameter shows whether the MOST network is closed and communication possible.
7. If the parameter shows that the MOST network is not closed, check the receiving control module in the same way as described above.

If menu text is displayed, communication on the MOST network is OK. The cause of the fault then lies in the media player module (MPM). Continue fault tracing by checking the component.

If menu text is not displayed, communication on the MOST network is not OK. The cause of the fault then lies in the next control module. Continue fault tracing by checking the fiber optic cable.

Checking the cable 

• Inspect the MOST connection for dirt, loose contacts and damage.
• If no fault can be found in the MOST connection, change the MOST cable.

Checking the component 

• Check the media player module (MPM) power supply and ground connection.
• Inspect the MOST connection for dirt, loose contacts and damage.
• If no fault can be found, change the media player module (MPM).

Remedy as necessary.

Click on the VCT2000 symbol to obtain a MOST network status reading.

Other information 

• see GENERAL AUDIO PLAYER MODULE
• see CHECKING THE SUPPLY VOLTAGE/GROUND TERMINAL
• see SIGNAL SPECIFICATION
• see DIAGNOSTIC INSTRUCTIONS - FIBRE OPTIC CABLE
• see FIBER OPTIC CABLE HARNESS, REPAIRING
• For information on the location and arrangement of MOST control modules, see COMPONENT LOCATIONS .

• Continue 

  Refer to VERIFICATION 

• Ignition off
• Unplug the MOST cable connector from the infotainment module (TCM).
• Ignition on
• Activate the infotainment system.

  Visually check that the infotainment control module (TCM) emits light from the MOST connector.

  If no light is emitted by the infotainment control module (ICM) then the control module is damaged.

  If the infotainment module (ICM) does emit light, the fault lies in the MOST cable to the next control module.

  Inspect the MOST connection for dirt, loose contacts and damage.

  If no fault can be found in the MOST connection, change the MOST cable.

  Remedy as necessary.

  Other information 

  • see INFORMATION AND ENTERTAINMENT DISPLAY
  • see FIBER OPTIC CABLE HARNESS, REPAIRING
  • For information on the location and arrangement of MOST control modules, see COMPONENT LOCATIONS .

• Continue 

  Refer to VERIFICATION 

Checking fuses 

Check that the fuse for the function in question is intact.

Replace the fuse if it is damaged.

Checking the cause of the fault 

Check the cause of the fault as follows:

1. Ignition off
2. Unplug the MOST connector from the multimedia module (MMM).
3. Connect the MOST cable to special tool see 9512867 .
4. Ignition on
5. Activate the infotainment system.
6. Check that MOST network communication is in working order. Do this by obtaining a status reading of the MOST locked parameter for at least 30 seconds. This parameter shows whether the MOST network is closed and communication possible.
7. If the parameter shows that the MOST network is not closed, check the receiving control module in the same way as described above.

If menu text is displayed, communication on the MOST network is OK. The cause of the fault then lies in the multimedia module (MMM). Continue fault tracing by checking the component.

If menu text is not displayed, communication on the MOST network is not OK. The cause of the fault then lies in the next control module. Continue fault tracing by checking the fiber optic cable.

Checking the cable 

• Inspect the MOST connection for dirt, loose contacts and damage.
• If no fault can be found in the MOST connection, change the MOST cable.

Checking the component 

• Check the multimedia module (MMM) power supply and ground connection.
• Inspect the MOST connection for dirt, loose contacts and damage.
• If no fault can be found, change the multimedia module (MMM).

Click on the VCT2000 symbol to obtain a MOST network status reading.

Remedy as necessary.

Other information 

• see CONTROL MODULE INFORMATION AND ENTERTAINMENT
• see CHECKING THE SUPPLY VOLTAGE/GROUND TERMINAL
• see SIGNAL SPECIFICATION
• see FIBER OPTIC CABLE HARNESS, REPAIRING
• see DIAGNOSTIC INSTRUCTIONS - FIBRE OPTIC CABLE
• For information on the location and arrangement of MOST control modules, see COMPONENT LOCATIONS .

• Continue 

  Refer to VERIFICATION 

Checking fuses 

Check that the fuse for the function in question is intact.

Replace the fuse if it is damaged.

Checking the cause of the fault 

Check the cause of the fault as follows:

1. Ignition off
2. Unplug the MOST connector from the integrated audio module (IAM).
3. Connect the MOST cable to special tool see 9512867 .
4. Ignition on
5. Activate the infotainment system.
6. Check that MOST network communication is in working order. Do this by obtaining a status reading of the MOST locked parameter for at least 30 seconds. This parameter shows whether the MOST network is closed and communication possible.
7. If the parameter shows that the MOST network is not closed, check the receiving control module in the same way as described above.

If menu text is displayed, communication on the MOST network is OK. The cause of the fault then lies in the integrated audio module (IAM). Continue fault tracing by checking the component.

If menu text is not displayed, communication on the MOST network is not OK. The cause of the fault then lies in the next control module. Continue fault tracing by checking the fiber optic cable.

Checking the cable 

• Inspect the MOST connection for dirt, loose contacts and damage.
• If no fault can be found in the MOST connection, change the MOST cable.

Checking the component 

• Check the integrated audio module (IAM) power supply and ground connection.
• Inspect the MOST connection for dirt, loose contacts and damage.
• If no fault can be found, change the integrated audio module (IAM).

Click on the VCT2000 symbol to obtain a MOST network status reading.

Remedy as necessary.

Other information 

• see GENERAL AUDIO PLAYER MODULE
• see CHECKING THE SUPPLY VOLTAGE/GROUND TERMINAL
• see SIGNAL DESCRIPTION, INTEGRATED AUDIO MODULE (IAM)
• see FIBER OPTIC CABLE HARNESS, REPAIRING
• see DIAGNOSTIC INSTRUCTIONS - FIBRE OPTIC CABLE
• For information on the location and arrangement of MOST control modules, see COMPONENT LOCATIONS .

• Continue 

  Refer to VERIFICATION