ME engine speed signal, function - GF07.61-P-3017MAS

ENGINE 156.984 in MODEL 216.377, 221.077 /177 as of Model Year 09 /AEJ 08 

Engine speed signal unction requirements, general 

• Circuit 87 M ON (engine control ON)
• Engine running

Engine speed signal, general 

Using the signal from the crankshaft Hall sensor (B70), the ME-SFI control unit (N3/10) generates the short-circuit-proof engine speed signal (TN) (e.g. for mechanical testing and diagnosis) and sends it as a direct signal.

Engine speed signal function sequence 

A voltage pulse (AC voltage) is generated in the crankshaft Hall sensor by the stays on the increment wheel (perforated plate) for a turning crankshaft. Here each stay generates a voltage pulse. No voltage is generated as a result of the gap created by 2 missing stays.

The engine speed signal is a square wave signal with a constant duty cycle of 6 pulses per engine revolution (60° CKA (C  rank A  ngle)) and maximum current about 20 mA.

If the voltage pulse fails from the crankshaft Hall sensor, voltage pulses from the intake camshaft Hall sensors, on the left and right (B6/4, B6/5) are used instead (for limp-home mode) or used by the exhaust camshaft Hall sensors, on the left and right (B6/6, B6/7).

The engine speed signal can be read out at the data link connector (X11/4) using commercially available diagnostic units.

Signal assignment 

Fig 1: Identifying ME Engine Speed Signal Assignment

Courtesy of MERCEDES-BENZ USA