Design [2 of 4]

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). At 0 °C, the voltage is approximately 4.0 V. At 100 °C the voltage is approximately 0.5 V. Low temperature results in high voltage (high resistance), high temperature 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




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
- turbocharger (TC) boost pressure (turbocharged engines only)
- 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 consists of a plastic housing with connectors, test electronics and an aluminum heat sink. The test electronics in the mass air flow (MAF) sensor consist of a hot film comprised of four resistors. The hot film is cooled by the air flow to the engine.
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 analog and varies between approximately 1-5 V depending on the air mass. Low air flow (low mass) results in low voltage, high air flow (high mass) gives high voltage. No air flow gives a reading of approximately 1 V.
The mass air flow (MAF) sensor is positioned between the air cleaner (ACL) housing and the intake manifold.
The shape of the mass air flow (MAF) sensor is slightly different on naturally aspirated engines and also contains an air temperature sensor.
The engine control module (ECM) can diagnose the mass air flow (MAF) sensor. The signal can be read using VIDA.

Boost pressure sensor





Overview
The boost pressure sensor is a combined sensor and contains two sensors in the same component:
- manifold absolute pressure (MAP) sensor
- temperature sensor.
The boost pressure sensor is on the right-hand upper section of the charge air cooler (CAC).

Manifold absolute pressure (MAP) sensor
The manifold absolute pressure (MAP) sensor detects the pressure in the intake manifold downstream of the charge air cooler (CAC). The signal from the sensor is primarily used by the engine control module (ECM) to check that the correct boost pressure is reached. The boost pressure is governed by the turbocharger (TC) control valve.
The sensor, which is a piezo resistor, is grounded in the control module and supplied with 5 V from the control module.
The resistance in the sensor changes depending on the pressure in the intake manifold, giving a signal of 0.5-4.5 V. Low pressure results in low voltage, high pressure on high voltage.
The engine control module (ECM) can diagnose the manifold absolute pressure (MAP) sensor. The sensor signal can be read using VIDA.

Temperature sensor
The temperature sensor detects the temperature of the intake air after the charge air cooler (CAC). This data is used by the engine control module (ECM) to calculate the boost pressure control and to calculate the 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.

Leak diagnostic unit (certain markets only)




The function of the leak diagnostic unit is to pressurize the fuel tank system during leak diagnostics.
The leak diagnostic unit consists of a plastic housing with:
1. electrical air pump
2. a valve / solenoid which governs the air flow in the unit
3. a heater element (PTC resistor) which warms up the pump.
The electrical pump, valve and heater element in the unit are supplied with voltage by the system relay. The pump, valve and heater element are grounded (control) in the engine control module (ECM).
When leak diagnostics are not active, the valve is held open to ambient air for EVAP control to be carried out.
During leak diagnostics the pump in the leak diagnostic unit starts. The valve in the unit is operated by the engine control module (ECM) by grounding the different circuits internally in the engine control module (ECM).
The Engine control module (ECM) checks the fuel tanks system for leaks by pressurizing the system and at the same time monitoring a number of relevant parameters. Also see: Leak diagnostics (certain markets only) Leak Diagnostics (Certain Markets Only)
The engine control module (ECM) can diagnose the leak diagnostic unit.
The valve in the leak diagnostic unit can be activated.
The leak diagnostic unit is at the upper front edge of the fuel tank.

Engine speed (RPM) sensor




The engine speed (RPM) sensor provides the Engine Control Module (ECM) with information about the speed and position of the crankshaft. The engine control module (ECM) is able to use the signal from the engine speed (RPM) sensor to determine when the piston in cylinder 1 is approaching top dead center (TDC). However it is unable to use the signal from the engine speed (RPM) sensor to determine whether the piston is in the combustion stroke or whether the exhaust valve is open (exhaust stroke). The signal from the camshaft position (CMP) sensor is also required to determine the operating cycle of the engine.
The signal from the engine speed (RPM) sensor is also used to check the engine for misfires. For more information, see: Misfire diagnostic Misfire Diagnostics
There is a steel ring with stamped holes welded to the rim of the primary section (the section fixed to the crankshaft) of the flywheel.
The holes are positioned with a gap of 6° between each hole. This arrangement creates a hole for each tooth. There are 360° in one revolution. 6° between each hole means that there are 60 holes. However two holes are not stamped, to create a reference position (long gap - missing tooth) for the crankshaft. The first tooth after the reference position is located 84° before TDC on cylinder 1. See: Function Function
The engine speed (RPM) sensor is at the rear of the engine above the flywheel.
The sensor is inductive with a permanent magnet. An alternating current is induced in the sensor when the flywheel/carrier plate passes the engine speed (RPM) sensor. The generated voltage and frequency increases with the engine speed (rpm).
The signal varies between 0.1-100 V depending on the engine speed (RPM).
The Engine Control Module (ECM) is able to determine the engine speed (RPM) by counting the number of holes per time unit. When the reference position passes the engine speed (RPM) sensor, the voltage and frequency drop momentarily to zero, even though the engine is still running. This allows the engine control module (ECM) to determine the position of the crankshaft.
If the signal from the engine speed (RPM) sensor is incorrect or missing, the control module will use the signals from the camshaft position (CMP) sensor, on the condition that the position of the camshaft has been adapted. This means that the car can be driven if the signal is missing.
The engine control module (ECM) can diagnose the engine speed (RPM) sensor. The sensor value (engine speed (rpm)) can be read off using VIDA.