Diagnosis fault memory, ME-SFI function - GF07.61-P-2004V

ENGINE 272.942 in MODEL 171

ENGINE 272.963 in MODEL 171

Illustrated on model 171

Fig 1: Diagnosis Fault Memory, ME-SFI Function - Illustrated On Model 171

Courtesy of MERCEDES-BENZ USA

The ME-SFI [ME] control unit checks its input and output signals for plausibility and recognizes possible faults. The detection of faults and their storage is differentiated in:

Faults constantly present

Loose contact fault (only on coolant temperature sensor (B11/4) and accelerator pedal sensor (B37))

The following components and systems are monitored:

Oxygen sensors
Catalytic converters
TWC heater
Secondary air injection
Smooth running control (combustion misfire)
Fuel system
Control units which are linked via the data bus
bus

Fault recognition

The following faults and error states are detected:

Signals above or below the limit value (open circuits, short circuits, faulty sensor)
Frequency of fault
Illogical combination of signals
Function chains with faults
Fault messages of all systems transmitted via CAN data bus (control units)
Fault states from the alternator (G2) with interface controller

Fault display via engine diagnosis indicator lamp or CHECK ENGINE

If an exhaust gas relevant error occurs or if it was already stored in the

In the event of a fault which could damage the catalytic converter, the driving cycle, the indicator lamp lights up in the instrument cluster. the engine diagnosis indicator lamp flashes.

The indicator lamp goes out after 3 correct, successive driving cycles.

Fault storage

Recognized faults are stored when they arise for the first time with their environmental data in the fault memory. If the fault is not confirmed during the following driving cycle, it is deleted. Emission-relevant faults are always entered, they have a high priority.

After 40 correct driving cycles an exhaust gas relevant fault and after 80 correct driving cycles a TWC damaging fault is erased from the fault memory.

Read out the fault memory

The ME-SFI [ME] control unit is connected via a serial interface (K-line) to the data link connector. The stored faults can be read out and deleted with STAR DIAGNOSIS or with a standard output device (generic scan tool) with "Ignition ON" or with the engine running via the data link connector (SAE standard ISO 9141-2).

The fault memory is not erased if the vehicle battery is disconnected.

Emergency running

If a fault is detected, substitute values are formed for the emergency running and the engine diagnosis/CHECK ENGINE indicator lamp lights up.

ME-SFI control unit after-running

After faults are erased it is necessary to wait until the processor has completed its power-down sequence after the ignition is switched off. The duration is dependent on the coolant temperature and is between 5 and 150 seconds.

Component description for the ME-SFI [ME] control unit		GF07.61-P-6000V
Component description for the "CHECK ENGINE" indicator lamp	At	GF54.30-P-5011V