ME-SFI diagnosis fault memory function

P07.61-3251-05

Shows model 219

0100 STAR DIAGNOSIS

A1 Instrument cluster

A1e26 "CHECK ENGINE" MIL

A1e58 Engine diagnosis indicator lamp

N3/10 ME-SFI [ME] control unit

N10/1 Driver-side SAM control unit with fuse and relay module

N93 Central gateway control unit

X11/4 Data link connector

CAN Data bus

The ME-SFI control unit checks its inputs and outputs for plausibility and recognizes possible faults. The identification of faults and their storing is differentiated as follows:
 Faults permanently existing

 Loose contact faults.

Reading out fault memory

The faults stored can only be read out at the data link connector with ignition "ON" or with "engine running" using the STAR DIAGNOSIS.

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In line with legal requirements, faults can also be read at the data link connector conforming to the SAE standard with a generic scan tool.

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Fault recognition

 Signals above or below limit value

(open circuit in wiring, short circuit, sensors faulty)

 Frequency and duration of fault

 Illogical combination of signals

 Closed loop (e.g. lambda control) at upper or lower control stop

 Function chains with fault

 Fault messages via CAN data bus from other control units.

Fault storage

Faults detected for the first time are written to the fault memory first of all as "suspected fault" together with the fault freeze frame data. 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 fault freeze frame data.

Faults which no longer occur are erased automatically from the fault memory after max. 40 warming-up phases.

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Function chains are test sequences, e.g. for air injection, purge system and leaktightness of evaporative emission control system, activated by the ME-SFI control unit.

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 ended. This ensures that no consequential faults are stored.

Emergency running

If a fault is detected, substitute values are formed. The indicator lamp in the instrument cluster only lights up, if the fault was already stored.

ME-SFI control unit afterrunning

After ignition is switched off, the computer starts to power down. During this period, the fault memory is overwritten. The duration is dependent on the coolant temperature: approx. 4 seconds at 80°C,

approx. 60 seconds at 20°C and approx. 150 seconds at - 30°C.

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A warming-up phase is completed:

 Coolant temperature at start less than 35°C

 Heating of the coolant to more than 70°C.

Actuation of the fault indicating lamp of the engine diagnosis or

CHECK ENGINE (MIL) 

The indicator lamp continues to light up after the engine start if the fault was already stored in the last driving cycle .

The malfunction indicator lamp comes on immediately when the engine is running if TWC damaging misfiring is detected.

The CHECK ENGINE MIL or engine diagnosis goes out if no further fault is detected during 3 driving cycles.

A driving cycle always refers to a single check and consists of:

 Engine start

 particular test performed

 engine turned off.

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Fault freeze frame data/operating conditions

The following data are stored if a fault is recognized:

 Fault code

 Vehicle speed

 Engine speed

 Coolant temperature

 Intake air temperature

 Intake manifold pressure

 Engine load status

 Throttle valve angle

 Ignition angle

 Gear engaged (automatic transmission)

 Mixture formation adaptation value

 Status of lambda control

- Lambda control not enabled

- Lambda control enabled

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

- Lambda control inhibited (e.g. if fault detected)

- Lambda control without correction of O2 sensor downstream of TWC

 Environmental conditions (e.g. tank fill level, time following end of start period, route covered when fault entered, clear counter status for faults or fault frequency, variable intake manifold position, purging or air injection active).

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If the same fault reappears, then the freeze frame data is saved again when the fault reappears. If the fault continues to occur, this second freeze frame data record is continuously overwritten and the fault frequency is exponented.

 Readiness/function 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 if the following tests are completed (result of test of no significance):

 Catalytic converter efficiency

 Purge control

 Secondary air injection

 Exhaust gas recirculation

 O2 sensor upstream of TWC, signal

 O2 sensor upstream of TWC, sensor heater.

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With discontinuity of the voltage supply for the engine control unit, the readiness code (readiness/function code) is reset.

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All tests for fault recognition

Fault code

()

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Individual test in driving-cycle takes place (cycle flag = 1).

Fault memory:

 No fault detected: clear suspected fault?

 Fault detected: Entry in diagnostic trouble code memory with freeze frame data

 Fault already stored?

 Number of warming-up phases

 Number of driving cycles for respective test.

Actuation of the indicator lamp

CHECK ENGINE  or engine diagnostics

 Readiness/function code

Tests completed for

 Catalytic converter efficiency

 Purge control

 Secondary air injection

 O2 sensor upstream of TWC, signal

 O2 sensor upstream of TWC, sensor heater

Data link connector

Read out with STAR DIAGNOSIS

also with generic scan tool

Data link connector

Read out with STAR DIAGNOSIS

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