This function is used to check that the chassis number and coding data between the CAS-control unit and the combination instrument is OK.
The kilometre reading is stored in several of the vehicle's control units, but the memory component for the kilometre reading is located on the combination instrument's circuit board. The memory component can only be written once and cannot be erased. However, it is possible to manipulate the kilometre reading but not without dismantling the combination instrument, which usually leaves visible traces.
Each time the ignition is turned on the data information between the CAS-control unit and combination instrument is checked. If a deviation is identified, a manipulation point is turned on in the combination instrument.
The manipulation point is turned on in the following cases:
The combination instrument has another chassis number than that stored in the CAS-control unit.
In one of the two control units there is no chassis number stored (e.g., a new part that is not coded).
In the combination instrument the component for storing the total kilometre reading is defective (then kilometre reading is shown with 999999 in the combination instrument).
If you suspect that the kilometre reading has been manipulated, the following checks can be performed:
Visual check with the combination instrument installed:
Check if the combination instrument's pointers stand at an angle or if the zero-point positions are not exact, the pointers are installed by machine and the tolerances for deviations are very small.
Check if there is damage, fingerprints, or scratches on the pointer's backing or on the inside of the cover lens.
Check that the pointers do not rub against the cover lens. This is especially important for the pointer for instantaneous consumption.
Checking via diagnostics:
Run the function "Checking vehicle's coding data" to check that the coding data is OK.
Run the combination instrument's self-test to see if all pointers move smoothly.
Checking dismantled combination instrument:
Check the pointer's distance to the pointer backing. The distance to the pointer backing is always the same.
Look for broken off or scratched lock lugs on the back of the combination instrument's casing and check if the instruction plate is damaged or attached poorly.
Check through the ventilation groove on the back of the combination instrument if the circuit board looks modified or if additional electronic equipment is installed.
NOTE! This is only one helpful way to find a possibly manipulated instrument. Detection of damage may be the result of other repairs to the vehicle.
The vehicle's stored coding data is checked to see that it is OK.
If the coding data is OK, the stored chassis number from the CAS-control unit is shown as well as the stored kilometre reading from the combination instrument.
If the coding data is not correct, an error message is shown instead.