Part 4

Design (Continued)

Engine coolant level sensor




The function of the engine coolant level sensor is to alert the driver if the engine coolant level in the expansion tank is too low.
The sensor is a magnetic reed switch, which is enclosed in a pipe on the bottom of the expansion tank. Around the pipe, on the inside of the expansion tank is a float. This float contains a magnet. When the engine coolant level is above minimum, the float is too high in the tank to affect the switch. However if the engine coolant level falls below the minimum level, the magnetic field acts on the switch.
The sensor is supplied with voltage (signal) from the Engine Control Module (ECM) and grounded in chassis. When the engine coolant level in the expansion tank is over a certain level the circuit closes, which produces a low signal. When the engine coolant level is below a certain level the circuit is opened by the engine coolant level sensor, which produces a high signal. When the engine control module (ECM) detects a high signal the information about low engine coolant level is transmitted via the Controller area network (CAN) to the driver information module (DIM), which warns the driver.

Note! There are no functions controlled by the engine which are directly connected to the low coolant level warning lamp. The Engine Control Module (ECM) only transfers the signal which is used by the Driver Information Module (DIM).

The engine control module (ECM) cannot diagnose the engine coolant level sensor.

Main relay (system relay)




The function of the main relay (system relay) is to supply certain components with voltage.
The relay is mechanical and has a closing function. In the rest position the circuit in the relay is open.
The main relay terminals (#30 and #86) are supplied with voltage by the battery. When the ignition key has been turned and the engine control module (ECM) is powered, the terminal (#85) on the main relay is grounded by the engine control module (ECM).
When the terminal (#85) is grounded, the relay is activated and a number of components are powered via the relay terminal (#87).
The engine control module (ECM) can diagnose the main relay.
The main relay is in the relay/fusebox in the engine compartment.

Air conditioning (A/C) relay




The air conditioning (A/C) relay controls the A/C compressor. When the climate control module (CCM) requests A/C control, a signal is transmitted to the engine control module (ECM) via the controller area network (CAN) to activate the relay. The engine control module (ECM) temporarily deactivates the relay in the event of:
- full load acceleration
- too high engine coolant temperature.
The relay is mechanical. It has a closing / breaking function and is supplied with power from the system relay.
In the rest position the circuit in the relay is open.
The system relay supplies the coil and the relay with power. The relay activates when the coil is grounded in the engine control module (ECM), the circuit closes and the A/C compressor is supplied with power via the relay voltage output.
The relay coil is grounded (signal) when the engine control module (ECM) receives a signal via the Controller area network (CAN) from the climate control module (CCM) to activate the relay and start the compressor.

Fuel pump (FP) relay




The fuel pump (FP) relay supplies the fuel pump with power. The relay also cuts the power to the pump when the ignition is switched off or if the engine stops. The central electronic module (CEM) also cuts the power to the relay if the supplemental restraint module (SRS) transmits a message indicating that an airbag has deployed.
See "Design and Function, Central electronic module (CEM)".
The central electronic module (CEM) activates and deactivates the relay when requested by the engine control module (ECM) (via the Controller area network (CAN)).
See Design and Function, central electronic module (CEM).
When the ignition is switched on, the engine control module (ECM) sends a signal to the central electronic module (CEM) via the controller area network (CAN) to run the fuel pump (FP) for one seconds. This is so that the pressure increases in the fuel system, shortening the start time.
When the flywheel in the engine rotates (generating a signal from the engine speed (rpm) sensor), the engine control module (ECM) will transmit a request to the central electronic module (ECM) via the Controller area network to start the fuel pump (FP). In the event of the engine stopping, the Engine Control Module (ECM) cancels the "activated fuel pump" signal. The central electronic module (CEM) then switches off the fuel pump (FP).
There is a directly connected cable between the engine control module (ECM) and the central electronic module (CEM). In the event of a fault in the Control area network (CAN), this cable is used by the "activated fuel pump" signal.

Air distribution valve




Cars from model year 1999-2000 have an air distribution valve. The air distribution valve supplies the injectors with air. This results in better volumetric efficiency, more effective combustion and therefore cleaner exhaust emissions. The valve is also used for idle air trim but is also slightly open at higher engine speeds.
The valve is directly mounted on the inlet hose for the electronic throttle module (ETM). The valve is connected to a hose which supplies air to the air-shrouded injectors via a distribution pipe.
The valve has its own ignition driver stage and solenoid and is supplied with 12V. The valve is controlled steplessly by the Engine Control Module (ECM) using a variable pulse ratio (duty-cycle) which opens or closes a shutter in the valve.
The valve works primarily during cold starts and when idling, to minimize the release of carbon dioxide and hydro-carbons whilst maintaining performance and driveablity. This is partly because the size of fuel drops is smaller with fuel mixed with air and does not adhere as easily to the walls of the intake manifold when they are cold and damp. This also reduces fuel consumption when cold starting and cuts the warm up time for both the engine and the three-way catalytic converter (TWC).
The total calculated volume of air to be released into the combustion chamber is distributed between both the Electronic Throttle Module (ETM) and the air distribution valve. The input signals to the Engine Control Module (ECM) which affect the operation of the air distribution valve are: the position of the throttle, engine speed (RPM)/position sensor, engine coolant temperature (ECT) sensor, ambient air pressure and ambient air temperature.
The air distribution valve can be diagnosed by the Engine control module (ECM) and can be activated using VIDA.

Injectors




The function of the injectors is to spray fuel into the cylinders in the correct spray patterns. This happens sequentially.
The injectors are in the intake manifold.
It is essential that the injectors are correctly installed with no air leakage around them. Fuel leakage from the top of an injector when it is not activated may lead to starting and driving problems.
The engine control module (ECM) controls the injectors using a pulse width modulation (PWM) signal.
The engine control module (ECM) can diagnose the injectors. The injectors can be activated using VIDA.

Air-shrouded injectors
Cars from model year 1999-2000 have air-shrouded injectors.
The injectors are in the air distribution pipe which is in the intake manifold.
The lower section of the injectors has 2 openings in the side where air can enter.
When the needle in the injector starts to rise, the openings are exposed. This allows air to flow in to the center of the valve at high speed, and the fuel and air are finely distributed and mixed.
When the needle rises further, the injector nozzle opens and the air/fuel mixture is released into the combustion chamber.

Evaporative emission system (EVAP) valve




The evaporative emission system (EVAP) valve is used to open/close the connection between the EVAP canister and the intake manifold. The valve controls the flow of hydro-carbons (fuel vapor) from the EVAP canister to the engine intake manifold using the vacuum in the intake manifold. This ensures that hydro-carbons stored in the EVAP canister are used in the engine combustion process.
The valve is an electro-magnetic valve which is powered from the system relay. When the valve needs to be opened, it is grounded internally in the engine control module (ECM). The evaporative emission system (EVAP) valve is closed when in the standby position (open-circuit).
When the control module requests that the EVAP canister should be emptied (the hydrocarbons stored in the canister should be released into the engine), the control module deploys the evaporative emission system (EVAP) valve by grounding it. The valve is grounded using a pulse width modulation (PWM) signal, allowing the control module to govern the extent to which the valve opens and adapting the emptying of the canister according to how full it is, engine speed (rpm) and load etc.
The engine control module (ECM) can diagnose the evaporative emission system (EVAP) valve. The valve can be activated using VIDA.
The evaporative emission system (EVAP) valve is close to the intake manifold.

Camshaft reset valve (Continuous variable valve timing (CVVT))




The camshaft reset valve controls the oil flow to the continuous variable valve timing (CVVT) unit.
The valve consists of an electro-magnetic valve with a spring-loaded piston. There are slits in the piston which channel the engine lubricating oil to different channels in the continuous variable valve timing (CVVT) unit by moving the piston in the reset valve. The continuous variable valve timing (CVVT) unit turns the camshaft (the cam timing changes). The direction in which the camshaft turns depends on the chamber in the CVVT unit which is supplied with oil (pressure).

The system relay supplies the reset valve with voltage. The valve is grounded (control stage) in the engine control module (ECM). When the valve is grounded using a pulse width modulation (PWM) signal, the oil flow in the valve can be controlled to the different chambers in the continuous variable valve timing (CVVT) unit at variable rates. This allow the angle of the camshaft to be changed precisely and smoothly.
The engine control module (ECM) can diagnose the camshaft reset valve. The value of the reset valve can be read using VIDA.
Only cars of model year 2000 and later have continuous variable valve timing (CVVT).
The valve is on the cylinder head above the camshaft with camshaft control.

Ignition coils




The ignition coils ignite the fuel / air mixture on command from the engine control module (ECM). The signal is re-transmitted so that the control module knows that it worked.
Each ignition coil has its own integrated power stage.
The ignition coils are in the sparkplug wells above each spark plug.
The ignition windings can be diagnosed by the Engine control module (ECM) and can be activated using VIDA.

Emissions warning lamp




The emissions warning lamp in the Driver Information Module (DIM) has a warning symbol. This warning symbol varies depending on the market and model year. The warning symbols are:
- "Engine symbol" (not USA, model year 2001-)
- "CHECK ENGINE" (MIL - Malfunction Indicator Lamp, USA only).
- "Lambda symbol" (not USA, model year 1999-2000).
The warning symbol lights when the ignition key is turned to position II and goes out when the engine is started if the engine management system does not detect any faults.
The warning lamp is directly connected to the engine control module (ECM).
The warning lamp will light if there is a fault in one of the monitored parameters in the engine management system. The warning lamp will also light in response to a request transmitted via the Control area network (CAN) if there is a fault in one of the following systems which affects emissions:
- gearbox control module (TCM)
- brake control module (BCM)
- electronic throttle module (ETM).

Manifold absolute pressure (MAP) sensor




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) as an addition to the mass air flow (MAF) sensor to calculate the 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 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 in high voltage.
The engine control module (ECM) can diagnose the manifold absolute pressure sensor. The sensor signal can be read using VIDA.
The manifold absolute pressure (MAP) sensor is on top of the radiator and is connected to the intake manifold by a hose.

Fuel tank pressure sensor (certain markets only)




The fuel tank pressure sensor detects the pressure in the fuel tank. The signal from the sensor is used by the engine control module (ECM) during diagnostics to check for leakage in the fuel tank system.
The sensor, which is a piezo resistor, is grounded in the control module and supplied with power from the control module.
The resistance in the sensor changes depending on the pressure in the fuel tank, giving a signal of 0.5 - 4.5 V. Low pressure results in low voltage, high pressure in high voltage.
The tank pressure sensor can be diagnosed by the Engine control module (ECM), and the sensor's signal can be read using VIDA.
The fuel tank pressure sensor is positioned on top of the fuel tank on cars with leakage diagnostics for the evaporative emission (EVAP) system.

EVAP canister shut-off valve (certain markets only)




The EVAP canister shut-off valve is used to close the connection between the EVAP canister/fuel tank system and fresh air (atmospheric pressure) when leak diagnostics are carried out on the cars with the evaporative emission (EVAP) system.
The valve is an electro-magnetic valve which is powered from the system relay. When the valve needs to be closed, it is grounded internally in the engine control module (ECM). The valve is open when in the rest position (open-circuit).
The valve can be diagnosed by the engine control module (ECM) and can be activated using VIDA.
The valve is next to the EVAP canister on cars with leak diagnostics for the evaporative emission (EVAP) system.