ICM-U1A1587 Incomplete Most Ring Reported By ICM. Bus Signal / Message Failures. Missing Message (2012): Fault-Tracing: Information: Overview
The infotainment control module (ICM) has detected an open-circuit in 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 a control module for any reason is unable to receive or send signals on the MOST-net or if there is an open circuit on the fiber-optic line, then Infotainment control module (ICM) will shut off all functionality.
Communication on the fiber optic net is one-directional. The control modules on the MOST-net receive the light signals, amplify them and then send them on. 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 be caused by interference at start up of the MOST network (ECM) or can be a different type of fault which occurs on different occasions. The fault is evaluated depending on how it occurs. If the fault recurs, fault-trace for permanent faults.
An intermittent fault may be difficult to diagnose using ring break diagnosis because a condition for this is that the fault occurs while the diagnostics program is running. If the fault is permanent, perform a ring break diagnostic to locate the open-circuit.
- Continue
Refer to CHECKING FOR OPEN-CIRCUITS