ME-SFI diagnosis fault memory function

P07.61-2789-05

0100 STAR DIAGNOSIS

A1 Instrument cluster

A1e26 CHECK ENGINE malfunction indicator lamp (for )

A1e58 Engine diagnosis indicator lamp (except )

K40/4 Passenger-side fuse and relay module, (model 230)

K40/7 Right front fuse and relay module (model 215, 220)

N3/10 ME control unit

N10/1 Driver-side SAM control unit with fuse and relay module
(model 211, 219)

N10/1 Front signal acquisition and actuation module (SAM)
(model 463)

X11/4 Data link connector

CAN Databus (Controller Area Network)

K K-Line

The ME control unit checks its input and output signals for plausibility and recognizes possible faults.

The monitored components and systems are:

 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)

Fault recognition

 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 databus (control units)

 Fault states from the alternator (G2) with interface controller

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Fault storage

The faults and their storage are differentiated in:
 There are continuous faults

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

Faults detected are stored in the fault memory as a fault together with freeze frame data. If the fault is not confirmed in the subsequent driving cycle, it is erased. Emission-relevant faults are always entered, they have a high priority.

Actuation of the engine diagnosis malfunction indicator lamp

or in case of  the CHECK ENGINE indicator lamp

If there is an exhaust-related fault in two consecutive driving cycles, the indicator lamp in the instrument cluster lights up. In the event of a fault which could damage the catalytic converter, the engine diagnosis indicator lamp flashes.

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Driving cycle

Systems that are not constantly monitored are checked only when a driving cycle is executed.

A driving cycle for a test consists of:

 Engine start (cold start)

 City cycle

 Outer city cycle

 engine switched off

As the required operating conditions are not always given, all the tests are also not completed in one drive.

Function chains

Function chains are test sequences triggered by the ME-SFI [ME] control unit, for example, for air injection, regeneration and

in case of , leaktightness of the fuel evaporation control system.

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Fault freeze frame data/operating conditions

If a fault is detected, the following data are stored:

 Fault code

 Vehicle speed

 Engine speed

 Coolant temperature

 Boost air temperature

 Intake/charge air pressure

 Engine load status

 Throttle valve angle

 Air recirculation flap angle

 Ignition angle

 Gear selected

 Mixture formation adaptation value

 Lambda control status (for example: lambda control blocked, enabled or disabled; fuel shutoff; without correction of O2 sensors downstream of the catalytic converter (G3/5, G3/6))

 Environmental conditions (for example, fuel tank level; distance in the case of a fault entry; counter readings for fault frequency; regeneration or air injection system active)

 Alternator voltage

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Consequential faults

If a faulty signal is detected and the corresponding fault code is stored, all the tests in which the signal is required as a comparative parameter are aborted. This ensures that no consequential faults are stored.

Readiness code

This code makes it possible to recognize that tests relating to fault recognition are in progress and the system is thus active.

The code is set once the following tests are completed (result of test not significant):

 Catalytic converter effect

 Purge control

 Secondary air injection

 O2 sensors signal upstream of the catalytic converter (G3/3, G3/4)

 Sensor heater for O2 sensors upstream of the catalytic converter

Emergency running

If a fault is detected, substitute values are formed for the limp-home, and the engine diagnosis indicator lamp or in case of , the CHECK ENGINE indicator lamp lights up.

Reading out fault memory

The ME-SFI [ME] control unit is connected to the data link connector via the K-LINE (as per SAE norm ISO 9141-2). Stored faults can be read out and deleted with STAR DIAGNOSIS or with a standard read-out device (generic scan tool) at "ignition ON" or when the engine is running.

ME-SFI control unit afterrunning

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 at -30 °C approx. 150 s and at 80 °C approx. 30 s.