Part 1
Faulty signal
951 2867 MOST instrumentation 951 2867 MOST Instrumentation
Checking the wiring and component
The infotainment control module (ICM) has detected an open-circuit in communication on the MOST network.
The MOST network is a fiber optic ring network. This means that all control modules which are connected to the network must be powered and grounded for the infotainment system to work. If, for any reason, a control module is unable to handle (receive or transmit) signals onwards on the MOST network, or if there is an open-circuit in the fiber optic cable, the infotainment control module (ICM) will shut down all functionality.
Communication on the fiber optic net is one-directional. The control modules on the MOST network receive light signals, amplify them and then send them onwards. The MOST connectors for the control modules contain two fiber optic cables, one for incoming and one for outgoing signals.
If the fault is intermittent, it has been registered previously but is no longer present. Intermittent faults can either be caused by interference when starting the MOST network, or by intermittent faults in the power supply/ground for one of the control modules in the network. The fault is evaluated depending on how it occurs. If the fault recurs, fault-trace for permanent faults.
It can be difficult to diagnose intermittent faults using a ring break diagnostic because for this to work the fault must occur during the diagnostic.
If the fault is permanent, perform a ring break diagnostic to locate the open-circuit.
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Continue - Checking for open-circuits
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Checking for open-circuits
Ring break diagnostic
A ring break diagnostic should be run to determine whether the fault has occurred.
To carry out a full ring break diagnostic of the MOST system, proceed as follows:
1. Switch off the ignition and remove the key
2. Remove the fuse for the AM/FM tuner module (AFM) and the traffic message channel module (TMC)
3. Wait at least 3 minutes
4. Ignition on
5. Reinstall the fuse for the AM/FM tuner module (AFM) and the traffic message channel module (TMC) within 25 seconds
6. Wait at least 30 seconds after switching on the ignition before reading off the position of the open-circuit.
Other information
- For information about fuses, see the wiring diagram.
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Continue - Reading off the position of the open-circuit
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Checking cable and component
If the result of the ring break diagnostic is POOR, the infotainment control module (ICM) is receiving a signal on the MOST network. However it is unable to decode the signals because the luminance of the signals is too weak or the signals are distorted.
If the result from the ring break diagnostic is OK, the fault is intermittent.
Fault-tracing using the ring break diagnostic assumes that the fault is permanent or active when the test is run, i.e. the system is powered having been off.
Hint: If diagnostic trouble code (DTC) ICM-DC01 is intermittent, read off the status of the ring break diagnostic from the frozen values in Vehicle communication.
Note that the AM/FM tuner module (AFM) and the traffic message channel module (TMC) are not normally included in a ring break diagnostic if the fuse is not removed. This means that the position of the open-circuit moves two steps backwards in the MOST network.
On fully equipped vehicles, if the open-circuit position is 5, this may be because of:
- Multimedia module (MMM)
- The fiber optic cable between the multimedia module (MMM) and the AM/FM tuner module (AFM)
- AM/FM tuner module (AFM)
- The fiber optic cable between the AM/FM tuner module (AFM) and the traffic message channel module (TMC)
- Traffic message channel module (TMC)
- The fiber optic cable between the traffic message channel module (TMC) and the audio module (AUD).
Check the communication on the MOST network by bypassing the control modules one by one on the MOST network as follows:
- Ignition off
- Disconnect the MOST connector from the relevant control module
- Connect the MOST cable to special tool 951 2867 MOST instrumentation 951 2867 MOST Instrumentation
- Ignition on
- Activate the infotainment system
- Check that the communication on the MOST network is functioning by reading off the status of the MOST locked parameter for at least 30 seconds. The parameter indicates whether the MOST network is closed and communication possible.
If the communication on the MOST network is stable when a control module is disconnected, check the power supply and the ground terminal on the relevant control module. Check for intermittent faults. Try replacing the component if no fault is found.
Click the VCT2000 symbol to read off the status of the MOST network.
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Continue - Verification
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Reading off the position of the open-circuit
- Ignition on.
Reading off the result from a ring break diagnostic
Click the VCT2000 symbol to read off the result of the ring break diagnostic.
The following result can be obtained from a ring break diagnostic:
If the fault occurs when the ring break diagnostic is run, the result will be presented as an open-circuit position.
If the fault does not occur when the ring break diagnostic is run, the result will be OK. If this is the case, select alternative 3 below.
- If the diagnostic indicates an open-circuit in the communication on the MOST network, the result will be an open-circuit position
- The result will be OK if there is no fault on the MOST network
- If the infotainment control module (ICM) receives a signal on the MOST network but is unable to decode it because the luminance is weak or the signals are distorted, the result will be POOR.
Determining the position of the open-circuit
The position of the open-circuit is calculated by working backwards in the MOST network from the infotainment control module (ICM).
Note! The ring break diagnostic always counts backwards, irrespective of which, or how many control modules, are installed in the car. To determine the position of the open-circuit, check the list to see which control modules are installed in that particular car. Then count backwards following the determined order. The number of control modules can vary between 4-9.
Two examples are outlined below:
- The first open-circuit position corresponds to 0. This means that the open-circuit is in the media player module (MPM) or in the cable between the media player module (MPM) and the infotainment control module (ICM)
- If the position is 1, go one step backwards in the chain. The open-circuit is in the phone module (PHM) or in the cable between the phone module (PHM) and the media player module (MPM). The open-circuit may be caused by the optical connector in the media player module (MPM) being damaged. This means that the media player module (MPM) is not able to interpret the incoming signal from the phone module (PHM) correctly.
Note! The phone module (PHM) is not standard. If one is not installed, the open-circuit position is in the subwoofer module (SUB). If only the 4 nodes in the standard set up of the MOST network are installed, open-circuit position 1 applies to the audio module (AUD).
Select the alternative for the control module to be checked.
Alternative 1:
Media player module (MPM).
Phone module (PHM).
Subwoofer module (SUB).
Global positioning system module (GPS).
Alternative 2:
Audio module (AUD).
Traffic message channel module (TMC).
AM/FM tuner module (AFM).
Multimedia module (MMM).
Infotainment control module (ICM).
Alternative 3:
The result from the ring break diagnostic indicates that the MOST network is OK.
The result from the ring break diagnostic is POOR.
Other information
- For information about location and order of control modules in the MOST network, see Location of components Component Location, Infotainment
Välj alternativ.
1 - Checking cable and component
2 - Checking cable and component
3 - Checking cable and component
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Checking cable and component
Select the control module to be checked from the list.
1. Media player module (MPM).
2. Phone module (PHM)
3. Subwoofer module (SUB)
4. Global positioning system module (GPS)
Välj styrenhet.
1 - Checking cable and component
2 - phone module (PHM)
3 - subwoofer module (SUB)
4 - global positioning system module (GPS)
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Checking cable and component
Select the control module to be checked from the list.
1. Audio module (AUD)
2. Traffic message channel module (TMC)
3. AM/FM tuner module (AFM)
4. Multimedia module (MMM)
5. Infotainment control module (ICM)
Välj styrenhet.
1 - audio module (AUD)
2 - traffic message channel module (TMC)
3 - AM/FM tuner module (AFM)
4 - Checking cable and component
5 - Checking cable and component
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Checking cable and component
Checking the fault cause
Check the fault cause as follows:
1. Ignition off
2. Disconnect the MOST connector from the media player module (MPM)
3. Connect the MOST cable to special tool 951 2867 MOST instrumentation 951 2867 MOST Instrumentation
4. Ignition on
5. Activate the infotainment system
6. Check that the communication on the MOST network is functioning by reading off the status of the MOST locked parameter for at least 30 seconds. The parameter indicates whether the MOST network is closed and communication possible
7. If the parameter displays that the MOST network is not correctly connected, check the receiving control module in the same way as above.
The communication on the MOST network is working if the menu text is displayed. If this is the case, the fault cause is in the media player module (MPM). Continue the fault-tracing by checking the component.
The communication on the MOST network is not working if the menu text is not displayed. The fault cause is then in the MOST cable for the next control module. Continue the fault-tracing by checking the fiber optic cable.
Checking cable
- Check the MOST connection. Check for dirt, loose connections and damage
- Replace the MOST cable if no fault is found in the MOST terminal.
Checking the component
- Check the power supply and the ground terminal for the media player module (MPM)
- Check the MOST connection. Check for dirt, loose connections and damage
- Replace the media player module (MPM) if no fault is found.
Remedy as necessary.
Click the VCT2000 symbol to read off the status of the MOST network.
Other information
- Media Player Module (MPM), replacement Media Player Module (MPM), Replacement
- Checking the supply voltage/ground terminal Component Tests and General Diagnostics
- Signal specification Pinout Values and Diagnostic Parameters
- Diagnostic Instructions - Fibre Optic Cable Diagnostic Instructions - Fibre Optic Cable
- Fiber optic cable harness, repairing Fiber Optic Cable Harness, Repairing
- For information about location and order of control modules in the MOST network, see Location of components Component Location, Infotainment
Väj Fortsätt.
Continue - Verification
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Checking the cable and component, phone module (PHM)
Checking the fault cause
Check the fault cause as follows:
1. Ignition off
2. Disconnect the MOST connector from the phone module (PHM)
3. Connect the MOST cable to special tool 951 2867 MOST instrumentation 951 2867 MOST Instrumentation
4. Ignition on
5. Activate the infotainment system
6. Check that the communication on the MOST network is functioning by reading off the status of the MOST locked parameter for at least 30 seconds. The parameter indicates whether the MOST network is closed and communication possible
7. If the parameter displays that the MOST network is not correctly connected, check the receiving control module in the same way as above.
The communication on the MOST network is working if the menu text is displayed. If this is the case, the fault cause is in the phone module (PHM). Continue the fault-tracing by checking the component.
The communication on the MOST network is not working if the menu text is not displayed. The fault cause is then in the MOST cable for the next control module. Continue the fault-tracing by checking the fiber optic cable.
Checking cable
- Check the MOST connection. Check for dirt, loose connections and damage
- Replace the MOST cable if no fault is found in the MOST terminal.
Checking the component
- Check the power supply and the ground terminal for the phone module (PHM)
- Check the MOST connection. Check for dirt, loose connections and damage
- Replace the phone module (PHM) if no fault is found.
Click the VCT2000 symbol to read off the status of the MOST network.
Remedy as necessary.
Other information
- Phone Module (PHM) Phone Module (PHM)
- Checking the supply voltage/ground terminal Component Tests and General Diagnostics
- Signal specification Pinout Values and Diagnostic Parameters
- Fiber optic cable harness, repairing Fiber Optic Cable Harness, Repairing
- Diagnostic Instructions - Fibre Optic Cable Diagnostic Instructions - Fibre Optic Cable
- For information about location and order of control modules in the MOST network, see Location of components Component Location, Infotainment
Välj Fortsätt.
Continue - Verification
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