Instruments - Speedometer Needle Vibrates

Service Measure Instruments

M62 200 04

March 11, 2004

Subject
R50, R53; speedometer needle vibrates

Complaint

Speedometer vibrates for five seconds when the engine is started.

The fault occurs intermittently.

Vehicles concerned: R50 and R53

Cause

1. Calibration process (design issue)

2. Software problem

Measure

Cause 1:

To avoid there being an imprecise zero position, there are two possible calibration processes for the speedometer needle:

a) Brief recalibration

All needles (including speedometer needle) drop once to the lower stop.

This takes place automatically when the ignition is switched back on after the K-bus has been in sleep mode.

b) Long recalibration

Speedometer needle vibrates or fluctuates for approximately 5 to 10 seconds. This takes place under following conditions:

- If the power supply to the instrument cluster has been disconnected.

- After a battery disconnection

- After a fuse for the instrument cluster has been replaced

- Blown instrument cluster fuse (it is assumed that the speedometer functions correctly when the ignition is switched on despite the blown fuse)

- Temporary drop in the instrument cluster voltage to less than 8.5 Volt Both of these processes are normal for the instrument cluster.

Cause 2:

If the fault cannot be explained by the calibration process described above, do not replace any parts.

This Service Measure will be updated as soon as additional information is available.