ME-SFI diagnosis fault memory function

The ME-SFI control module checks its inputs and outputs for plausibility and detects possible faults.

When detecting faults and storing them, the following distinction is made:

 Faults which are constantly present

 Loose contact faults

Reading fault memory

It is only possible to read and erase the stored faults with the HHT with ignition "ON" or with "engine running" at the datalink connector.

 The fault memory is erased in the ME-SFI control module if the vehicle battery is disconnected (interruption of circuit 30).

Recognition of faults

 Signals above or below limit value (open circuit wiring, short circuit, faulty sensors)

 Frequency and duration of the fault

 Illogical combination of signals

 Function chains with fault

 Fault messages through CAN databus from the ETC control module or from the DAS control module

-----------------------------------------------------------------------------------------

Storing faults

When a fault is detected for the first time, it is written to the fault memory together with the ambient data initially as a "suspected fault". If the fault is not confirmed in the subsequent driving cycle, it is erased. If the fault is confirmed, it is stored together with its ambient data.

Faults which no longer occur are automatically erased from the fault memory after not more than 40 warming-up phases.

A warming-up phase is completed if

 coolant temperature at start < 35 °C

 coolant heated up to > 70 °C

A driving cycle for a test consists of

 engine start

 the particular test performed

 engine switched off

A trip is completed if

 all tests and function chains of the emission-relevant faults have been completed at least once since engine start

 time after start > 20 minutes

 engine temperature >= 70 °C

 engine speed > 500 rpm

-----------------------------------------------------------------------------------------

Ambient data/operating conditions

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

 Fault code

 Vehicle speed

 Engine speed

 Coolant temperature

 Intake air temperature

 Intake manifold pressure

 Engine load state

 Ignition angle

 Adaptation value of mixture formation

 Lambda control state

- Lambda control not enabled

- Lambda control enabled

- Lambda control inhibited (e.g. in the case of fuel shutoff or fault detected)

 Further environmental conditions (e.g. fuel tank level, time after end of start, distance since erasing last fault, counterreadings for erasing faults or fault frequency)

Function chains

Are test sequences activated by the ME-SFI control module, e.g. for camshaft timing, purge control and leaktightness of evaporative emission control system.

Consequential faults

If a fault signal is detected and the corresponding fault code is stored, all the tests for which the signal is required as a comparative parameter, are aborted. This prevents consequential faults being stored.

Emergency running mode

If faults are detected, substitute values are formed. The malfunction indicator lamp in the instrument cluster only comes on if the fault was already stored.