Reading Off The Position Of The Open-Circuit

• Ignition on.

Reading off the result from a ring break diagnostic 

Click the VCT2000 symbol in VIDA (Volvo scan tool) to read off the result of the ring break diagnostic.

The following results can be obtained from a ring break diagnosis:

• If the diagnostic detects a communication failure on the MOST network, the result will be the name of the control module positioned before the failure.
• The result will be OK if there is no fault on the MOST network.
• If the Infotainment control module (ICM) gets a signal on the MOST-net, but is unable to decode the signals due to the light intensity being too weak or the signals are too distorted, the result becomes poor signal  .
• If all control modules on the MOST network believe that they are slave nodes the result is diag all units slave  .
• If one or several control modules on the MOST-net consider themselves master nodes, the result becomes diagnosis multimaster  .

Determining the position of the open-circuit 

The Ringbreak diagnostic works so that after the control modules have been powered down and then restarted, each control module on the MOST-circuit sends its address to the Infotainment control module (ICM). This means that if the configuration is as illustrated in the figure, the Remote Digital Audio Receiver (RDAR) will send first followed by the Multimedia module (MMM). The break is in the node before the one specified as the result in the diagnostic, alternatively in the cable between them All communication occurs clockwise in the loop illustrated. 

An example is given below.

• The result of the diagnostic is "AUU", which means Accessory USB unit (AUU). If the MOST configuration is as illustrated, this means that the break is in the Integrated Audio Module (IAM) or in the cable between Integrated Audio Module (IAM) and Accessory USB unit (AUU). The break may even be due to the optical contact in the Accessory USB unit (AUU) or in the Integrated Audio Module (IAM) being damaged.

Select the relevant alternative.

Alternative 1 

Infotainment Control Module (ICM).

Refer to CHECKING CABLES AND COMPONENTS, INFOTAINMENT CONTROL MODULE (ICM) 

Alternative 2 

Integrated audio module (IAM).

Multimedia module (MMM).

Bluetooth phone module (BPM).

Audio Control Module (AUD).

Accessory USB unit (AUU).

Phone module (PHM)

Remote Digital Audio Receiver (RDAR).

Refer to NO COMMUNICATION 

Alternative 3 

The result from the ring break diagnostic indicates that the MOST network is OK.

The result from the ring break diagnostic displays a poor signal.

The result from the ring break-diagnosis shows diagnosis multimaster.

Refer to CHECKING THE CABLE AND COMPONENT 

Alternative 4 

The result from the ring break-diagnosis shows diagnosis all units slave.

Refer to CHECKING THE INFOTAINMENT CONTROL MODULE (ICM)