Scan Tool Connecting (Connection and Use of Test Equipment)
ME-SFI diagnosis fault memory function
ENGINE 104.941 /943 /944 /991 /994as of 1.8.96
ENGINE 104.995
with CODE (494a) USA version
with CODE (807) Model year 1997
with CODE (808) Model year 1998
ENGINE 111.921 /942 as of 1.9.98,
111.943,
111.944 as of 1.8.96,
111.946 as of 1.6.98,
111.947 /973,
111.975 as of 1.8.96
ENGINE 111.945
in MODEL 208.335/435 as of 1.6.98,
202.020 /080 as of 1.9.98
ENGINE 111.974
with CODE (494a) USA version
with CODE (807) Model year 1997
with CODE (808) Model year 1998
ENGINE 112.910 /911 /912 /913 /914 /916 /917 /920 /921 /922 /923 /940 /941 /942 /943 /944 /946 /947 /949 /953 /954 /955 /970 /972 /973 /975
ENGINE 113.940 /941 /942 /943 /948 /960 /961 /963 /965 /966 /967 /968 /969
ENGINE 119.980 /981 /982 /985
ENGINE 120.982/ 983
ENGINE 137.970
087 Hand-HeldTester HHT
094 Multiplex cable (can be connected to 16-pin data link connector using adapter)
K40 Relay module (model 170, 210 up to 2/97)
K40/4 Fuse and relay module (model 202, 210 as of 3/97, model 163 designation F1, model 215, 220 designation K40/7)
N3/10 ME-SFI control unit
N16/1 Base module (Model 129, 140, voltage supply of ME control unit)
X11/4 Datalink connector
X11/22 Diagnostic data link connector II
0100 STAR DIAGNOSIS
K40 Relay module (model 170)
K40/4 Fuse and relay module (Model 202, 208, 210)
N3/10 ME-SFI control unit
N10/1 Front SAM control unit with fuse and relay module (Model 203)
N10/1 SAM control unit with a fuse and relay module for the driver (type 211)
X11/4 Datalink connector
CAN Data bus
Shown on model 210
X11/22 Data link connector (further designation X11/4)
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.
Note: The diagnostic trouble code memory is erased when the vehicle battery is disconnected.
Reading out fault memory
The stored faults can only be read out and erased with the HHT or the STAR DIAGNOSIS when ignition is "ON" or when "engine running" at the diagnostic data link connector
(USA) In line with legal requirements, faults can also be read at the data link connector conforming to SAE standard, ISO 9141-2, with a generic scan tool.
Engine 120
The ME-SFI control units on the left (N3/11) and right (N3/12) feature a fault memory. All the faults together can be read out only from the right ME-SFI control unit (N3/12).
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
- Error messages via extremely fast data bus called CAN from control unit AT, ESP or IFRCL (Engine 120: Left ME control unit)
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.
Actuation of the CHECK ENGINE malfunction indicator lamp (USA)
Actuation of the engine diagnosis malfunction indicator lamp with low-emission EURO3/4
The indictor lamp in the instrument cluster comes on if the fault was already stored in the last driving cycle (USA model year 1996: during the last trip).
The "CHECK ENGINE" MIL (USA) or engine diagnosis at low emission EURO3/4 is quenching, if in the 3 driving cycles no fault is detected (USA model year 1996: during the last 3 trips).
A warming-up phase is completed:
- coolant temperature at start < 35°C
- Coolant has heated up to > 70°C
A driving cycle (driving-cycle) is always based on an individual test and consists of
- engine start
- Individual test performed
- engine turned off.
A trip (USA model year 1996) is completed if
- all tests and function chains of exhaust-relevant faults are performed at least once since engine start
- Time after start > 20 minutes
- Engine temperature greater than -7°C
- Engine speed > 500 rpm
Note: (USA) Since the criterion of trip (model year 1996) has been replaced by the driving cycle (driving-cycle), faults are stored and the CHECK ENGINE indicator lamp (MIL) is actuated more rapidly.
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 state
- Ignition angle
- Adaptation value of mixture formation
- Status of lambda control
- Lambda control not enabled
- Lambda control enabled
- Lambda control inhibited (e.g. if fuel shut off)
- Lambda control inhibited (e.g. if fault detected)
- Lambda control without correction of O2 sensor downstream of TWC
- Further environmental conditions (e.g. fuel tank level, time after end of engine start, erase distance since last fault, erase counter readings for faults or fault frequency)
Function chains are test sequences activated by the ME-SFI control unit, e.g. for secondary air injection, exhaust gas recirculation, camshaft timing, purge system and leaktightness of evaporative emission control system.
Consequential faults
If a faulty signal is recognized and the corresponding fault code is stored, all the tests which require this signal 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.
(USA) 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
- Regeneration
- Secondary air injection
- Exhaust gas recirculation
- O2 sensor upstream of TWC, signal
- O2 sensor upstream of TWC, sensor heater.
ME-SFI control unit afterrunning
After faults are erased, it is then necessary to wait until the processor has completed its afterrunning after the ignition is switched off. The time is dependent on the coolant temperature: at 80°C approx. 4 seconds, at 20°C approx. 60 s and at -30°C approx. 150 s.
