Powertrain Management: Description and Operation
GF07.61-P-2004GS ME-SFI Diagnosis Fault Memory Function
- ENGINE 111.981 in MODEL 203.747
- ENGINE 111.983 in MODEL 170.449
0100 STAR DIAGNOSIS
K40 Relay module (model 170)
K40/4 Fuse and relay module (Model 202, 208, 210)
N3/10 ME-SFI [ME] control module
N10/1 Front SAM control module with fuse and relay module (model 203)
X11/4 Data link connector
CAN data bus Controller Area Network
The ME-SFI control module checks its inputs and outputs for plausibility and detects possible faults. The recognition of faults and their storage is differentiated as follows:
- Fault constantly present
- Loose contact faults (only in the case of coolant temperature and pedal value sensor)
The fault memory is not erased if the vehicle battery is disconnected.
Reading out fault memory
The faults stored can only be read out and erased at the data link connector with ignition "ON" or with "engine running" using the STAR DIAGNOSIS.
(United State of America) In line with legal requirements, faults can also be read out at the diagnosis test connector conforming to SAE standard, ISO 9141-2, with a generic scan tool.
Fault recognition
- Signals above or below limit value (open circuit in wiring, short circuit, sensors faulty)
- Frequency with fault freeze frame data
- Illogical combination of signals
- Function chains with fault
- Fault messages over CAN databus from ETC, ESP or RFL/EIS/ IC/ESM control module
Fault storage
Faults detected are written to 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. Non exhaust-relevant faults are erased if there are more than 5 entries.
Actuation of the CHECK ENGINE malfunction indicator lamp Actuation of the engine diagnosis malfunction indicator lamp (in the case of low-emission EURO3/4)
The malfunction indicator lamp in the instrument cluster comes on if the fault was already stored in the last driving cycle.
A driving cycle for a test consists of
- Engine start
- particular test performed
- engine switched off
Fault freeze frame data/operating conditions
If 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 status
- Throttle valve angle
- Ignition angle
- Gear engaged (MT, AT, ESQ)
- Mixture formation adaptation value
- Status of lambda control
- Lambda control not enabled
- Lambda control enabled
- Lambda control disabled (e. g. in the case of fuel shutoff)
- Lambda control disabled (e. g. if fault detected)
- Lambda control without correction of O2 sensor downstream of TWC
- Further fault freeze frame conditions (e.g. fuel tank level, time after end of start, distance in the case of fault entry, counter readings for fault frequency, purging or secondary air injection active, emergency mode active)
Function chains are test sequences, e.g. for secondary air injection, purge system and leaktightness of evaporative emission control system, activated by the ME-SFI control module.
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 serves to ensure that consequential faults are not stored.
Limp-home mode
If a fault is detected, substitute values are formed. The malfunction indicator lamp in the instrument cluster comes on if the fault was already stored in the last driving cycle.
(United State of America) 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 once the following tests are completed (result of test not significant):
- Catalytic converter efficiency
- Purge control
- Secondary air injection
- O2 sensor upstream of TWC, signal
- O2 sensor upstream of TWC, sensor heater
