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Bus diagnosis

Bus diagnosis





In a bus system, all units must be capable of communicating with each other. For example, the engine cannot be started unless the Trionic system can receive the immobilization information sent out by the TWICE.

Bus faults can be caused by a bus lead breaking. This could result in one or more systems disappearing from the bus concerned (I or P), depending on where the break in the wiring harness occurred.

If a short circuit occurs in a bus lead, all systems will disappear from the bus concerned (I or P).

Note that if a short circuit occurs in the I bus, then the DICE is the only bus system which can be contacted with the diagnostic tool.

In the event of a grounding or power supply fault in one or more systems, these systems will no longer be able to communicate.

Permanent bus faults

All diagnostics communication with systems connected to a bus takes place via the DICE.

Irrespective of which system is contacted, the diagnostic tool will first check with the aid of the DICE that all systems in the car connected to a bus are awake and in communication.

If any control module connected to a bus is missing, the diagnostic tool will show this. This means that all control modules connected to a bus are communicating correctly unless the diagnostic tool indicates otherwise with a warning.

In the case of a permanent bus fault, the text on the diagnostic tool's display will refer to a fault diagnosis procedure described in the ”Bus and diagnostics communication” category.

Intermittent bus faults

The Trionic and TCM continuously check that all control modules from which they obtain information communicate correctly. In the case of intermittent faults in bus communication with any of these systems, diagnostic trouble codes will be generated in the Trionic and TCM. The cause of the fault could be that the control module concerned has lost its power supply or one of the bus leads.

In the case of an intermittent bus fault, the diagnostic trouble code text will refer to a fault diagnosis procedure described in the ”Bus and diagnostics communication” category.

Incorrect values on the bus

A diagnostic trouble code will be generated in the Trionic and TCM if any information they obtain from the bus has an incorrect value. The diagnostic trouble code text will refer to the system where the fault is present.