Displaying engine speed, function - GF54.30-P-3021Q

WARNING: This page is about a different car, the 2009 Mercedes-Benz CLK350 and 2008 Mercedes-Benz CLK350. However, it is still accessible from the selected car via links, so may be relevant.

Model 209.3 /4

Fig 1: Engine Speed Display Function Diagram

Courtesy of MERCEDES-BENZ USA

Networking

The engine speed is registered by the crankshaft position sensor (L5).

The signals from the crankshaft position sensor (L5) are read in by the motor electronics control unit (N3/10) or the CDI control unit (N3/9) and are transmitted as a CAN message (in RPM) on the engine compartment CAN.

The instrument cluster (A1) receives the CAN message and actuates the stepper motor of the tachometer (A1p5) relative to the engine speed.

Warning range

The warning range (marked red on the scale) begins below the full scale value in vehicles with

gasoline engines at 7000 RPM
diesel engines at 6000 RPM

Adjustment for the number of cylinders

It is not necessary to adjust the tachometer (A1p5) to the number of cylinders in the engine.

If implausible CAN messages occur, the needle of the tachometer (A1p5) is moved to the left-hand end of the scale. An error bit is also stored in the fault memory.

Instrument cluster (IC), location / task

GF54.30-P-3039Q