Part 1

Design

Ignition switch

The ignition switch powers certain functions in the engine control module (ECM) via fuses in the front integrated relay/fuse box and central electronic module (CEM). The ignition switch also supplies the engine control module (ECM) with signals such as:
- "wake up" signal
- start signal.

"wake up" signal
The ignition switch transmits a high signal (Ubat) to the engine control module (ECM) via the central electronic module (CEM) indicating that the ignition switch is in position I or II. The system prepares for start-up (for example by temporarily activating the fuel pump relay).

Start signal
The ignition switch transmits a high signal (Ubat) to the engine control module (ECM) when the ignition switch is in position III.
The engine control module (ECM) activates the starter motor relay. The relay in turn activates the starter motor. See also: Function Function
The fuse in the front integrated relay/fuse box supplies current to the ignition switch.
The central electronic module (CEM) has diagnostics for the ignition switch.

Transmission control module (TCM)

The engine control module (ECM) uses a directly connected signal from the transmission control module (TCM) in the start function (activating the starter motor). See also: Function Function

Immobilizer
See Design and Function, Immobilizer.

Alternator control module (ACM)
See Design and Function, Generator (GEN).

PremAir sensor (certain markets only) (2006-)

The function of the PremAir sensor is to meet legal requirements for low emission variants. The sensor is located on the radiator.
The sensor measures the temperature of the radiator and transmits the value, together with a check of its own condition, to the Engine control module (ECM). During the engine's warm-up phase the Engine control module (ECM) carries out a number of checks of the received information in order to determine the status of the sensor and the radiator.
The sensor communicates with the Engine control module (ECM) via LIN (Local Interconnect Network)communication, a standardized serial communication method. Transmitted information is encrypted.
The PremAir sensor is diagnosed by the Engine control module (ECM). The sensor is secured to the radiator and cannot be replaced separately.

Air conditioning (A/C) pressure switch

The air conditioning (A/C) pressure sensor detects the pressure in the low pressure side of the air conditioning (A/C) system. See also: Function Function
The air conditioning (A/C) pressure sensor has a pressure sensing switch which is supplied powered by the fuse and grounded (signal) in the engine control module (ECM). The air conditioning (A/C) pressure sensor is affected by the pressure in the low-pressure pipe of the air conditioning (A/C) system (thick pipe).
The engine control module (ECM) cannot diagnose the air conditioning (A/C) pressure sensor.

Oil pressure switch

The function of the oil pressure switch is to warn the driver about low oil pressure via the driver information module (DIM).
The oil pressure 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

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) voltage on the ground lead for the fuel pump. This means that the voltage drop across the pump changes, and with it the output of the fuel pump. See also: Function Function
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. See also: Fuel pressure regulation, diagnostics Fuel Pressure Regulation, Diagnostics
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 on the right-hand side of the fuel tank.

Fuel pump

The function of the fuel pump is to ensure that the pressure is correct at 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. It also contains a non-return valve which ensures that the pressure in the system 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. See also: Fuel pressure regulation, diagnostics Fuel Pressure Regulation, Diagnostics
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.

Stop lamp switch

The task of the stop lamp switch is to provide the engine control module (ECM) with information about the position of the brake pedal.
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 control module (BCM), design.
The stop lamp 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 can be read using VIDA.
The stop lamp switch is on the pedal box by the brake pedal.

A/C pressure sensor

The air conditioning (A/C) pressure sensor detects the pressure in the high-pressure side of the air conditioning (A/C) system. See also: Function Function
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 (between 0-5 V depending on the pressure in the air conditioning (A/C)) is transmitted to the control module. Low pressure produces low voltage, high pressure produces high voltage. The air conditioning (A/C) pressure sensor is affected by the pressure in the high-pressure pipe of the air conditioning (A/C) system (narrow pipe).
The engine control module (ECM) can diagnose the air conditioning (A/C) pressure sensor. The sensor value can be read off using VIDA.

Heated oxygen sensors (HO2S)

Front heated oxygen sensor (HO2S)

Caution! The air lines for the heated oxygen sensors must not be trapped or damaged in any way. The connectors for the heated oxygen sensors 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.

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). For more information, see: Three-way catalytic converter (TWC) diagnostics Three-Way Catalytic Converter (TWC) Diagnostics
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 must not be trapped or damaged in any way. The connectors for the heated oxygen sensors 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.

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. They are also pre-heated to ensure 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.
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, a 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) / engine cooling fan (FC) control module

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) has two functions. One is to cool the engine compartment, the other is to cool the condenser when the air conditioning (A/C) compressor is working.
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).

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.

Mass air flow 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 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 sensor is analogue and varies between approximately 0.5-4.5 V depending on the 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.

Temperature sensor
The temperature sensor checks the temperature of the intake air in the intake manifold. This data is used by the engine control module (ECM) to calculate injection period. The control module also controls certain diagnostic functions using the signal from the temperature sensor.
The sensor, which is an NTC resistor, is grounded in the control module and supplied with power (signal) from the control module.
The resistance in the sensor changes according to the temperature of the intake air. This provides the control module with a signal of between 0.5-5 V. The lower the temperature the higher the voltage (high resistance). A high temperature results in low voltage (low resistance).
The engine control module (ECM) can diagnose the temperature sensor. The sensor signal can be read using VIDA.

Manifold absolute pressure (MAP) sensor

The manifold absolute pressure (MAP) sensor is on top of the radiator and is connected to the intake manifold by a hose.
The manifold absolute pressure (MAP) sensor detects quick pressure changes in the intake manifold after the throttle. The signal from the sensor is used by the engine control module (ECM) to supplement the mass air flow (MAF) sensor when calculating injection period.
The semi-conductor sensor is grounded in the control module and is supplied with power from the control module.
The resistance in the intake manifold moves the silicone membrane in the sensor, giving a signal of 0.5 - 4.5 V. Low pressure results in low voltage, high pressure in high voltage.
The engine control module (ECM) can diagnose the manifold absolute pressure (MAP) sensor. The sensor signal can be read using VIDA.