The Siemens SIM 21 engine management system is used on the 1.3L Duratec 8V engine.
The SIM 21 PCM is located in the engine compartment on the battery housing and is equipped with a 94-pin connector.
The SIM 21 PCM monitors and processes the signals received from the sensors.
With the aid of the information from the sensors, the SIM 21 PCM can calculate the required quantity of injected fuel for every operating state of the engine.
The SIM 21 PCM can be diagnosed with WDS via the DLC.
Sensors
T-MAP
NOTE:During installation of the T-MAP sensor it is very important to ensure that the sensor is correctly seated in the intake manifold to ensure that no unmetered air can get into the intake manifold from the outside.
The T-MAP sensor is located on the rear side of the air intake module.
The sensor is capable of measuring both the absolute pressure in the intake manifold and the temperature of the intake air.
The housing of the T-MAP sensor contains a piezo pressure sensor element which detects the absolute pressure in the intake manifold, as well as the electrical circuits required to amplify this signal and the intake air temperature (IAT) sensor element (NTC resistor).
The T-MAP sensor is supplied with a reference voltage of 5 V from the PCM.
The output signal from the manifold absolute pressure (MAP) sensor element is an analogue voltage signal which changes proportionately to the current absolute pressure in the intake manifold.
- A high absolute pressure in the intake manifold (throttle valve wide open) means a high voltage,
- and a low absolute pressure in the intake manifold (throttle valve closed) means a low voltage.
Both with "ignition on, engine off" and while driving at "full throttle" the MAP sensor element measures the current atmospheric air pressure. This is stored in the RAM memory of the PCM and is used during the drive as a reference pressure value.
TP sensor
The TP sensor is part of the air intake module and is attached to the throttle valve housing.
It is a rotary potentiometer which is actuated via the throttle valve shaft.
It supplies information to the PCM about the current position of the throttle valve and the rate at which the throttle valve position is changing.
These signals are required to calculate the idle speed, the ignition timing and the injected fuel quantity.
ECT sensor
The CMP sensor is located in the cylinder head cover next to the intake cam of cylinder no. 1 and is an inductive sensor.
The CMP signal is used for the sequential fuel injection.
The PCM detects the zero point of the CMP signal (middle of reference cam) for detection of cylinder no. 1 at 10° after TDC.
As soon as the PCM has synchronised the CMP signal with the CKP signal, the sequential fuel injection begins.
If the engine is started without a CMP signal, then it is possible that the timing of the fuel injection will be out by a revolution of the crankshaft.
Failure of the CMP signal while the engine is running has no consequence, as the synchronisation takes place during the starting phase.
Upstream and downstream lambda probe
The upstream lambda probe is located at the top of the exhaust manifold.
Its signal is used to calculate the air/fuel ratio based on the oxygen content of the exhaust gases upstream of the catalytic converter.
The downstream catalytic converter is located in the exhaust pipe after the catalytic converter.
This signal is used to monitor the efficiency of the catalytic converter.
Both lambda probes are heated.
PSP switch
The CPP switch is located on the pedal box.
The PCM uses the signal from the CPP switch to determine whether the clutch is being engaged or disengaged.
The quantity of injected fuel is briefly reduced during actuation of the clutch to avoid engine judder during gearshifts.
Signal failure may result in engine judder during gearshifts.
Generator
NOTE:The VSS is only installed on vehicles without ABS.
The VSS is a Hall sensor which is located on the transmission housing.
The vehicle speed signal is required to calculate the idle speed and for the deceleration fuel shut-off.
In addition, the PCM also sends on a processed vehicle speed signal to the instrument cluster.
Actuators
Fuel pump relay
The fuel pump relay is located in the battery junction box.
When the ignition is turned to position "II" the fuel pump relay is energised for a few seconds via the PCM.
The fuel pump relay is continuously actuated during the start-up phase of the engine.
The voltage supply to the fuel pump relay is supplied via the inertia fuel shut-off switch.
Fuel injectors
The fuel injectors are located on the fuel distribution pipe, which in turn is part of the air intake module.
The injectors inject fuel once per operating cycle unless additional fuel is required for certain operating states (e.g. during acceleration etc.).
The fuel injectors are actuated cyclically by the PCM.
The quantity of injected fuel is regulated by the length of actuation of the fuel injectors.
IAC valve
