General

General
At series launch, the instrument cluster (basic) features two bus interfaces which enable the information link (data link/serial) to the connected control modules.

These busses are:
- K-bus (body bus)
- Diagnosis bus (link to diagnostic socket).

A further bus interface provides the link to the automatic transmission unless the instrument cluster has a CAN interface. On manual transmission vehicles, the reverse gear selector status is read in via this connection.

Coded data determining the scope of functions of the instrument cluster are stored in a non-volatile data memory (data is retained when supply voltage is disconnected).

The various scope of functions includes, for example, the vehicle model and the country language variant.

Replacing Instrument Cluster
The four cases described in the following show under which circumstances which steps must be taken to ensure correct replacement of the instrument cluster electronics.

Case 1: The instrument cluster control module is defective and the light check module control module (LCM) is OK.






Case 2: The instrument cluster control module is OK. and the light check module control module (LCM) is defective.






Case 3: The control module for the instrument cluster and the control module for the light check module (LCM) must be replaced.

Only replace both control modules at the same time if this is unavoidable (stored total odometer reading is irretrievably lost).

NOTE: Disconnect battery!






Case 4: As a check, replace the control module for the instrument cluster or the light check module control module (LCM).

NOTE: Although exchanging one of the two control modules is possible in principle, it should be avoided wherever possible.






Scope of function

The following are displayed or used for a function:

Part 1:

Part 2:

Test functions
The test functions which could be called up on the on-board computer in previous series can now be called up in the instrument cluster.

System test (test No. 2): The system test is used to test the display unit together with its elements which can be controlled from the instrument cluster.

These elements are:
- All pointer instruments
- All LC displays with a segment test and their background lighting

Indicator and warning lamps for:
- Belt warning
- Fuel reserve
- General brake warning lamp
- Parking brake
- Left and right turn signal indicators
- Front and rear fog light
- High beam
- Gear indicator (automatic transmission)
- Service interval display SIA
- Check control displays (if coded)
- Air suspension
- Fault automatic transmission
- Engine oil level

Pointer instruments: During the system test, operation of the pointer instruments is diagnosed and a corresponding fault code is set in the fault code memory if an electrical fault occurs. In addition, particular care must be taken to observe whether the pointers move smoothly and continuously over their entire indication range during the first test pass. During the second pass within a system test sequence, the pointer instruments are not moved continuously and smoothly over their entire indication range. In this case, the electrical drive data is measured at various indication angles of the pointers.