Part 1

Design

Ignition switch




The Engine Control Module (ECM) uses the signal from the ignition switch to detect when the ignition key has been turned to position II or III. When the key is in the ignition position (position II) or starting position (position III) a high signal (Ubat) is transmitted from the ignition switch to the engine control module (ECM). The engine management system prepares for start-up (for example, temporarily activates the fuel pump (FP) relay). When the flywheel in the engine rotates, the engine speed (RPM) sensor signal is used to keep the fuel pump (FP) relay activated.
The fuse in the fuse box in the passenger compartment supplies current to the ignition switch.
The central electronic module (CEM) has diagnostics for the ignition switch.

Immobilizer
See Design and Function, Immobilizer.

Oil pressure sensor




The function of the oil pressure sensor is to warn the driver about low oil pressure via the driver information module (DIM).
The oil pressure sensor switch has a pressure sensing switch which is powered (signal) by the engine control module (ECM) and grounded in the cylinder block. The oil pressure sensor is affected by the oil pressure of the engine.
When the oil pressure exceeds a certain value, the switch in the oil pressure sensor will open. A high signal is then sent to the engine control module (ECM).
If the oil pressure is below a certain value, the switch in the oil pressure sensor will close and a high signal will be sent to the engine control module (ECM). The engine control module (ECM) then transmits a CAN signal to the driver information module (DIM) to light the indicator lamp for low oil pressure.
The oil pressure sensor is on the cylinder block.
The engine control module (ECM) cannot diagnose the oil pressure sensor.

Fuel pump control module (only vehicles with demand controlled fuel pumps)




The fuel pump control module powers the fuel pump and regulates the output of the pump. The fuel pressure changes with the output of the pump.
The fuel pump control module is supplied with battery voltage by the fuel pump (FP) relay and is grounded in the car body. The fuel pump (FP) relay is controlled by the central electronic module (CEM) when requested by the engine control module (ECM).
The engine cannot be started if the power supply to the fuel pump control module is faulty because the fuel pump will not then be powered.
The fuel pump control module is controlled by the engine control module (ECM) via serial communication. The fuel pump control module then controls the fuel pump by transmitting pulse width modulated (PWM) signals on the ground lead for the fuel pump. This means that the voltage drop across the fuel pump changes, and with it the output of the fuel pump. See also: Function Function
The central electronic module (CEM) controls the fuel pump (FP) on models without on-demand fuel pumps.
There are no diagnostics for the fuel pump control module. The engine control module (ECM) has diagnostics for fuel pressure regulation and the associated components.
The pulse-width modulated (PWM) signal from the engine control module (ECM) to the fuel pump control module can be read using VIDA.
The fuel pump control module is on the outside of the fuel tank.

Fuel pump (only vehicles with demand controlled fuel pumps)




The central electronic module (CEM) controls the fuel pump (FP) on models without on-demand fuel pumps.
The function of the fuel pump is to ensure that the pressure is correct in the delivery lines for the injectors when requested by the fuel pump control module.
The fuel pump consists of:
1. An electrical pump with an integrated safety valve
2. A pressure equalization valve. This valve equalizes rapid pressure peaks which occur, for example, when the injectors close during engine braking. The built-in check valve ensures that the system pressure does not drop when the engine is switched off
3. Fuel level sensor
4. Fuel filter, cannot be replaced separately
5. Relief valve, releases fuel into the pump housing
6. Ejector pump, continuously fills the pump housing with fuel. The fuel always flows from the fuel pump through the ejector and back to the pump housing.
The fuel pump is supplied with battery voltage by the fuel pump control module and is grounded in the car body via the fuel pump control module.
The engine control module (ECM) has diagnostics for the fuel pump function to ensure that the pressure is correct.
The fuel pump can be activated and its status read off using VIDA.
The pressure in the fuel rail can be measured by connecting a manometer to a nipple. This nipple is on the right-hand end of the fuel rail.

Brake light switch




The purpose of the brake light switch is to provide the engine control module (ECM) with information indicating whether the brake pedal is depressed.
A signal is transmitted to the engine control module (ECM) when the brake pedal is pressed. The engine control module (ECM) disengages the cruise control (if activated). The brake pedal sensor also disengages cruise control. For further information, see Design and Function, Brake system, design.
The brake light switch is supplied with power from the ignition switch (terminal 30). When the brake pedal is depressed the switch closes and a high signal (12 V) is transmitted to the engine control module (ECM).
The engine control module (ECM) can diagnose the brake light switch. The status of the switch (pressed or not) can be read using VIDA.
The brake light switch is on the pedal box by the brake pedal.

Clutch pedal sensor (manual transmissions only)




The clutch pedal sensor provides the Engine Control Module (ECM) with information about the position of the clutch pedal.
This information is used by the control module to switch off the cruise control.
The sensor signal is also used by the control module to prevent engine start if the clutch pedal is not pressed (certain markets).
The sensor consists of a sliding potentiometer which is supplied with power by the control module (signal) and which is grounded in the control module.
The resistance in the sensor reduces as pressure increases on the clutch pedal.
The engine control module (ECM) can diagnose the clutch pedal sensor. The status (position) of the sensor can be read using VIDA.
The sensor is on the pedal box by the clutch pedal.

Air conditioning (A/C) compressor




The air conditioning (A/C) pressure sensor detects the pressure in the high-pressure side of the air conditioning (A/C) system.
The sensor is linear. It is grounded in the control module and supplied with a 5 Volt current from the control module. A linear signal (which depends on the pressure in the air conditioning (A/C) system) is transmitted to the engine control module (ECM). Low pressure produces low voltage, high pressure produces high voltage.
The engine control module (ECM) can diagnose the air conditioning (A/C) pressure sensor. The sensor value can be read off using VIDA.
The air conditioning (A/C) pressure sensor is positioned on the high pressure delivery line for the air conditioning (A/C) system.

Heated oxygen sensors (HO2S)

Front heated oxygen sensor (HO2S)




The front heated oxygen sensor (HO2S) is used to provide the engine control module (ECM) with information about the remaining oxygen content of the exhaust gases in front of the three-way catalytic converter (TWC). This is so that the Engine Control Module (ECM) can continually check the combustion so that lambda=1. lambda=1 is the ideal fuel-air ratio, with 14.7 kg air/1 kg fuel.
The heated oxygen sensor uses current regulation and its signal characteristic is linear. With a linear signal characteristic, the amplitude of the signal curve is low when changing the oxygen content in the exhaust gases. The probe consists of a preheating element (see "Pre-heating heated oxygen sensors (HO2S)") and the actual lambda sensor. The lambda sensor is an oxygen sensitive ceramic body consisting of zirconium oxide. The control module supplies power to the ceramic body, which reacts to the oxygen content of the exhaust gases. This in turn affects the signal to the engine control module (ECM). In order to determine the oxygen content in the exhaust pipe, the heated oxygen sensor needs reference air from the surrounding air. This reference air reaches the heated oxygen sensor via the air lines.

Caution! The wiring for the heated oxygen sensors (HO2S) must not be trapped or damaged in any way. The connectors for the heated oxygen sensors (HO2S) must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors (HO2S).

The engine control module (ECM) can diagnose the heated oxygen sensor (HO2S).
VIDA can be used to read off the calculated lambda value from the heated oxygen sensor.

Rear heated oxygen sensor (HO2S)




The rear heated oxygen sensor (HO2S) is used to provide the Engine Control Module (ECM) with information about the remaining oxygen content of the exhaust gases behind the three-way catalytic converter (TWC). This information is used by the Engine Control Module (ECM) to check the function of the three-way catalytic converter (TWC). This check is carried out when the conditions for the catalytic converter diagnostics have been met. The rear heated oxygen sensor (HO2S) has no direct effect on regulation of the fuel/air mixture. However the Engine Control Module (ECM) uses the signal to optimize the signal from the front heated oxygen sensor (HO2S).
The heated oxygen sensor (HO2S) uses voltage control. The signal characteristic is binary. With a binary signal characteristic, the amplitude of the signal curve changes considerably when changing the oxygen content in the exhaust gases. Otherwise its components and function are the same as the front heated oxygen sensor (HO2S).

Caution! The air lines for the heated oxygen sensors (HO2S) must not be trapped or damaged in any way. The connectors for the heated oxygen sensors (HO2S) must not be greased under any circumstances. The oil in the grease would disrupt the reference air and the function of the heated oxygen sensors (HO2S).

The engine control module (ECM) can diagnose the rear heated oxygen sensor. The signal can be read using VIDA.

Preheating of the heated oxygen sensors (HO2S)
The heated oxygen sensor (HO2S) only functions above a certain temperature, approximately 300 °C. The normal operating temperature is between 300-900 °C. The heated oxygen sensors (HO2S) are electrically pre-heated so that operating temperature is rapidly reached. This also ensures that the heated oxygen sensors (HO2S) maintain a normal operating temperature and to prevent condensation which could damage the heated oxygen sensor (HO2S).
The heater element in the probe consists of a positive temperature coefficient (PTC) resistor. The system relay supplies the heater element with voltage. The element is grounded in the engine control module (ECM). When the control module grounds the connection a current flows through the PTC resistor. When the heated oxygen sensor (HO2S) is cold, the resistance in the PTC resistor is low and a large current will flow through the circuit. The current from the Engine Control Module (ECM) is pulsed at first to prevent condensation damage to the heated oxygen sensor (HO2S). Depending on the temperature, allowances are made for factors such as the dew point. As the temperature in the PTC resistor rises, the resistance rises, the current falls and switches in stages to a constant current. The pre-heating time for the front heated oxygen sensor (HO2S) is short, approximately 20 seconds.
Probe preheating begins as soon as the engine is started. The heater element heats the heated oxygen sensors (HO2S) to approximately 350 °C. The probes maintain this as a minimum temperature.
The engine control module (ECM) can diagnose the heater element.

Engine coolant temperature (ECT) sensor




The engine coolant temperature (ECT) sensor checks the temperature of the engine coolant. The temperature of the engine coolant is required so that the engine control module (ECM) can regulate:
- the injection period
- the idle speed
- the engine cooling fan (FC)
- the ignition advance
- engagement and disengagement of the A/C compressor
- diagnostic functions.
The sensor is a negative temperature coefficient (NTC) type which is supplied with power from the control module (signal) and is grounded in the control module.
The resistance in the sensor changes depending on the temperature of the coolant. Depending on the resistance in the sensor, voltage (signal) is transmitted to the engine control module (ECM). The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).
The engine coolant temperature (ECT) sensor is located beside the thermostat.
The engine control module (ECM) can diagnose the engine coolant temperature sensor. The sensor value can be read off using VIDA.

Engine cooling fan (FC) control module




The engine cooling fan (FC) cools the coolant, engine compartment and the condenser when the air conditioning (A/C) compressor is running.
The engine control module (ECM) transmits a pulse width modulated (PWM) signal to the engine cooling fan (FC) control module. The control module then activates the fan at different speeds. The speed of the engine cooling fan (FC) is determined by the engine control module (ECM), depending on the coolant temperature (based on the signal from the engine coolant temperature (ECT) sensor) and the vehicle speed.
The temperature conditions for engagement of the different engine cooling fan (FC) stages may vary slightly, depending on the engine variant and the equipment level. The temperature conditions apply when:
- the A/C is off
- no faults are detected by the Engine Control Module (ECM).
There is an internal diagnostic function in the engine cooling fan (FC). This function transmits a signal to the engine control module (ECM) if the fan is partially or fully blocked. To do this, the engine cooling fan (FC) control module grounds the pulse width modulation (PWM) signal based on a predetermined pattern.

Note! The engine cooling fan may have a post-run of up to approx. 6 minutes after the engine has been turned off. The time for the fan's post-run depends on engine temperature, temperature in the engine compartment and pressure level in the AC-system.

Warning! Be careful since the engine cooling fan may have a post-run after the engine has been turned off.

The engine cooling fan (FC) and its control module are behind the radiator.
The engine control module (ECM) can diagnose the engine cooling fan. The fan can be activated using VIDA.

Cooling fan for control modules




The engine control module (ECM) is in a control module box in the engine compartment. The transmission control module (TCM) is also in this box in vehicles with automatic transmissions.
The function of the cooling fan is to cool the control modules in the control module box in the engine compartment. The control modules may be damaged if they overheat.
A temperature sensor is integrated in the engine control module (ECM). The engine control module (ECM) activates the fan if the control module registers that the temperature is too high. The fan then runs continuously until the temperature has dropped to a normal level.
The cooling fan is in the hose between the control module box and the firewall.
The engine control module (ECM) can diagnose the cooling fan. The fan can be activated using VIDA.
A diagnostic trouble code (DTC) is stored if the temperature in the engine control module (ECM) gets too high.

Mass air flow (MAF) sensor with integrated temperature sensor





Overview
The mass air flow (MAF) sensor on naturally aspirated engines is a combined sensor and contains two sensors in the same component:
- mass air flow (MAF) sensor
- temperature sensor.
The mass air flow (MAF) sensor is positioned between the air cleaner (ACL) housing and the intake manifold.

Mass air flow (MAF) sensor
The mass air flow (MAF) sensor gauges the air mass sucked into the engine. It continuously transmits signals to the engine control module (ECM) about the mass of the intake air. This data is used by the engine control module (ECM) to calculate:
- the injection period
- the fuel pressure
- the ignition timing
- the engine load.
The transmission control module (TCM) also uses this data for its gear shift calculations. This data is transmitted to the transmission control module (TCM) from the engine control module (ECM) via the high speed side of the Controller area network (CAN).
The mass air flow (MAF) sensor is a hot wire type. Unlike other hot wire types, the mass air flow sensor in the Denso system uses a hot wire which has a ceramic casing. This eliminates the need for a clean burn function.
The mass air flow (MAF) sensor is supplied with battery voltage by the system relay and is grounded in the engine control module (ECM). The signal from the gauge is analog. It varies depending on air mass. Low air flow (low mass) results in low voltage, high air flow (high mass) gives high voltage.
On turbocharged engines the mass air flow (MAF) sensor has a slightly different design. It is not a combined sensor and only contains sensors for the mass air flow.
The engine control module (ECM) can diagnose the mass air flow (MAF) sensor. The signal can be read using VIDA.