Computers and Control Systems: Description and Operation

Design

10 Inline injection pump
B11 Coolant temperature sensor
B17 Intake air temperature sensor
B28 Pressure sensor
B28/3 EGR lift sensor
CAN Data bus
K40 Relay module
L5/6 Crankshaft position sensor
N3/7 IFI control module
N14/2 Glow output stage
N15/3 ETC control module
R25/2 Accelerator pedal position sensor
S40 Cruise control switch
Y1/1 IFI electrohydraulic shutoff
Y1/1b1 Fuel temperature sensor
Y22/6 Resonance intake manifold switch over valve
Y22/7 Resonance intake line switchover valve
Y23/1 IFI fuel metering control
Y23/1I1 Fuel rack position sensor
Y31/1 EGR vacuum transducer
Y31/2 Pressure regulating flap vacuum transducer


NOTE: The on board diagnosis II (OBD II) functions are stored in the IFI control module (N3/7).

Task
Recognizing and storing faults in the fuel injection system. In addition, the ambient conditions when the fault occurs are also stored.

Function

Fault path tests
In certain operating states, fault paths are tested e.g. for short circuit, open circuit, implausible signals and illogical combinations.

Notes refault memory
- Fault memory: fault readout
current faults
stored faults
All inputs/outputs are checked for plausibility during operation. Any fault which exists is stored in the fault memory of the IFI control module (N3/7).
The faults remain stored when ignition "OFF" or after disconnecting the car battery.
In the case of exhaust-relevant faults, the
CHECK-ENGINE (A1e26)
malfunction indicator lamp and the readout
CHECK-ENGINE
ENGINE ELECTRONICS
in the multifunction display come on.
The faults are identified by an OBD fault code.
Such faults are e.g.:
- lift sensor B28/3
- EGR vacuum transducer Y31/1
- pressure regulating flap vacuum transducer Y31/2

Fault ambient data
With the HHT it is additionally possible to display the fault ambient data which existed at the time the fault was stored. Only those ambient data which existed when the fault first occurred, are stored. The ambient data are distributed over several image pages (up to 8 image pages), the last two image pages being intended solely for Development.
Image pages with the result V/F explain the causes of the fault e.g.:
- voltage too high
- voltage too low
- signal too large
- signal too small
- value implausible

Definition: test readiness
The corresponding fault path tests and function chains must have been fully conducted at least once after ignition ON up to ignition OFF (one operating cycle). Accordingly, two "completed" tests can only be achieved in two operating cycles.

Operating cycle
An operating cycle is achieved if the following conditions exist
- Coolant temperature > 60° C
- Switch off engine
- Wait 5 seconds after-running
- Start engine
- Run engine at idle speed for 20 seconds
- Rev up engine in P/N position to 2500 rpm and release accelerator
- Accelerate car in position D to about 70 km/h (WOT acceleration) and then move into deceleration mode up to about 60km/h.