Electronic Modules - Design and Function: Overview Volvo XC90 I

Scheme 1

The climate control unit consists of the following components

1. Heater element
2. Damper motor, temperature, left
3. Blower fan
4. Damper motor, fresh air / recirculation
5. Power unit for blower fan motor
6. Particle filter
7. Damper motor, ventilation and floor (also defroster for MCC/STD)
8. Damper motor, temperature, right
9. Damper motor defroster (ECC).

Engine coolant constantly flows through the heater element. There is no valve to regulate the flow. The selected temperature is achieved using dampers for the right and left-hand sides of the car installed upstream and downstream of the heater element. These control the amount of air to be warmed. There are also dampers downstream of the heater element that guide the airflow to the correct air vent.

The climate control module provides infinitely variable electronic blower fan control. When AUTO mode (only electronic climate control) is engaged the climate control module (CCM) adapts the blower fan speed to the setting of the controls and the vehicle speed. The blower fan can be set to run-on in order to reduce residual moisture in the evaporator.

A timer located in the central electronic module (CEM) controls the run-on time. 50 minutes after the engine has been switched off and the ignition has been turned to position 0 or I the central electronic module (CEM) supplies power to the climate control module (CCM) and the blower fan is activated at full speed for 7 minutes. This run-on dries the evaporator and prevents bad odors.

This function is programmed at the factory, but can be deactivated in the event of customer complaints via programming of customer parameters. Programming is carried out via VIDA (Volvo scan tool).

The function is only available to cars of structure week 199850 and later.

All damper motors are of the stepper type. Their position and speed is controlled electronically.

Manual climate control and standard climate control have four stepper motors controlling the following dampers

1. Ventilation / floor / defroster via a link system
2. Recirculation and fresh air via a link system
3. Temperature left
4. Temperature right.

For electronic climate control (ECC) there is an extra stepper motor which controls the defroster. The wiring between the damper motors and the climate control module (CCM) consists of four cables for supply voltage and directional control and a separate cable for each motor which controls the motor to be activated. Each motor has four coils. The corresponding coils in each motor are supplied with power at the same time. The motors are only supplied with power if they are grounded at the same time. When a new position is selected for the damper motor, the climate control module (CCM) calculates how many steps are required to complete the movement. The climate control module (CCM) then activates the damper motor with the necessary number of steps. When the motor is instructed to move to an end position, the motor is activated until it stops. This end position is then used as a limit position. This means that the damper motors are self-adjusting, but only after the limit positions have been reached. When replacing the damper motors, ensure that the self-adjustment is carried out. Otherwise the customer may experience defective climate control.

There are diagnostics for the blower fan and damper motors.

Scheme 2

The engine control module (ECM) controls the A/C compressor. When the A/C switch on the dashboard environment panel is activated, a request to activate the compressor is transmitted via Control area network (CAN) to the engine control module (ECM). The engine control module (ECM) determines when the compressor must operate.

If any of the following conditions are met the compressor is disconnected

1. High engine coolant temperature (ECT)
2. Wide open throttle (WOT)
3. The engine has just been started
4. Overpressure in the air conditioning (A/C) system.

When the engine is started the engine control module (ECM) activates the air conditioning compressor for a short period even if the climate control module (CCM) has not transmitted a request about this. This is carried out for diagnosis. This check is carried out at all temperatures exceeding -6 °C.

The advantage in allowing the engine control module (ECM) to control the air conditioning compressor is that it can delay compressor activation somewhat, if the idling speed must be compensated for the extra load for example.

Scheme 3

The sun sensor transmits information about sun intensity to the climate control module (CCM).

The sun sensor consists of a photo diode which is supplied with power from the control module. The conductivity of the diode depends on the amount of light to which it is exposed. The diode is located under a diffusing lens which reduces the sensitivity of the photo diode to the angle of the light hitting it. Increased sun intensity reduces the voltage over the photo diode. The control module measures the voltage over the photo diode and compensates for high sun intensity by lowering the ventilation air temperature, changing the distribution of air and increasing the speed of the blower fan.

The climate control module (CCM) starts to compensate the blower fan speed at a sun intensity of 400 W/m 2 and reaches maximum compensation at a sun intensity of 1000 W/m 2 .

The sun sensor is located in the middle of the dashboard by the windshield.

There are diagnostics for the sun sensor.

Scheme 4

The air quality sensor is available as an option for the electronic climate control from model year 2000. Its function is to transmit a signal to the climate control module (CCM) if it detects increased concentrations of pollutants in the outside air.

The air quality sensor measures the CO x and NO x content.

The air quality sensor compares current values with previous ones and can calculate changes in pollutant concentrations.

The signal from the air quality sensor to the climate control module (CCM) is a pulse width modulation (PWM) signal and has four stages, 0-3

1. signal 0= no increase in or reduced pollutant level
2. signal 1=gradual increase in pollutant level
3. signal 2=moderate increase in pollutant level
4. signal 3=rapid increase in pollutant level.

The control module uses the signal to control the recirculation damper motor.

The air quality sensor is located on the right-hand side of the fresh air intake under the cowl.

There are diagnostics for the air quality sensor.

Scheme 5

Across the lower section of the dashboard environment panel there is a 12V socket and space for a maximum of seven switches.

Each switch has its own identity. This is unique for the relevant function. The switches can therefore be positioned in any location on the dashboard environment panel, as long as they are installed in the off position. They do not have to be in any particular order. However, the identity of the installed switches must correspond with the car configuration file so that they can be activated.

There are diagnostics for the switches.

Scheme 6

XC90 with three rows of seats is equipped with a rear A/C system. This consists of

1. power unit
2. fan
3. expansion valve
4. blower fan switch.

The rear A/C system is controlled by a switch in the lower section of the dashboard environment panel. When the switch is activated the climate control unit (CCM) transmits a signal to the rear electronic module (REM) via the Control area network (CAN). The rear electronic module (REM) supplies the power unit and the blower fan switch with voltage via a relay. The blower fan switch sends control voltage to the power unit based on the position of the control. The power unit converts the control voltage to supply voltage for the blower fan motor.

The rear A/C is directly connected to the front air conditioning via the high and low pressure pipes and hoses. The only way to control the cooling in the third row of seats is to control the fan speed using the rear fan switch.

The rear electronic module (REM) diagnoses the relay supply, otherwise the rear A/C cannot be diagnosed.

DESCRIPTION OF PROGRAMMABLE PARAMETERS, CUSTOMER ADAPTATION

Certain parameters for the climate control module (CCM) can be read off and programmed using this function. The purpose of this programming is to

1. read the programmed parameters before replacing the control module. This is so the same parameters can be entered into the new control module
2. to adapt the function of the control module for the equipment levels of the car (passenger compartment ventilation filter, parking heater)
3. to adapt the function of the control module to the requirements of the driver.

Passenger compartment ventilation filter compensation, status

Indicates the status for the activation of passenger compartment ventilation filter compensation.

OFF = Compensation not active

ON = Compensation active (preset)

Blower fan run-on, status

Provides the status for activation of the blower fan run-on. The run-on dries the evaporator and prevents bad odors which may otherwise result from residual moisture in the system.

OFF = Run-on inactive

ON = Run-on active (preset)

Blower fan speed, value

Allows the speed to be modified for the blower fan when the climate control system is in AUTO mode. Modifying the parameters means that the climate control system either blows more or less air than the preprogrammed value, to correspond to the request of the driver.

Gives the voltage value for adaptation of the blower fan speed.

1.0 - +1.0 V (0 V preset)

Setting for air distribution for the floor / defroster residual heat, value

Indicates the setting of the air distribution between the floor and defroster.

10/90 - 90/10% (70/30% preset)

Setting for air distribution for the floor / defroster parking heater, value

Indicates the setting of the air distribution between the floor and defroster.

10/90 - 90/10% (70/30% preset)

Passenger compartment temperature, value

The passenger compartment temperature in relation to the passenger compartment temperature switch position can be adjusted by programming a compensation value.

The passenger compartment temperature can be raised or lowered by a maximum of ±2 °C (±4 °F) from the normal value. This allows the temperature to be adjusted in accordance with the driver's wishes.

0 = -1.0 °C/-2.0 °F

1 = -0.5 °C/-1.0 °F

2 = 0.0 °C / 0.0 °F (default value)

3 = +0.5 °C/+1.0 °F

4 = +1.0 °C/+2.0 °F

DESCRIPTION OF COMPONENTS/FUNCTIONS ACTIVATION

Self-adjustment of damper motors

This function can be used to carry out self adjustment of the limit positions for all the damper motors. Self adjustment must be carried out if, after checks, one or more of the damper motors do not reach their limit positions or the climate control module (CCM) is replaced. There are a number of possible reasons for a damper motor not reaching its end position. For example, the motor or the damper has been turned manually, the voltage supply may have been cut, or a component has been replaced.

GENERAL INFORMATION ABOUT READING OFF THE STATUS OF THE BUTTONS ON THE DASHBOARD ENVIRONMENT PANEL

The result from reading off the status for buttons on the dashboard environment panel in order from left to right.

TO DECIDE OPERATION CONDITIONS WHEN THE MALFUNCTION WAS DETECTED

Malfunctions in a system may be intermittent. It is important to remember this when troubleshooting a possible malfunction cause. If the malfunction is not in the vehicle when it is in the workshop you can miss a malfunction cause since the values may be correct when troubleshooting takes place. A good indication of when the malfunction first occurred for the first time are the frozen values that can be read out for every diagnostic trouble code.

The frozen values are stored immediately after a malfunction has been detected. Most parameters in the frozen values are the same for all malfunctions and indicate a general condition when a malfunction has been detected, e. g., engine rpm, load, coolant temperature, vehicle speed and battery voltage. Some of them have been selected to give a better understanding of the specific malfunction.

Diagnostic trouble code ECM-903F Electronic throttle unit, internal malfunction cam be used as an example of how frozen values can be used.

The first possible source indicated in VIDA is the voltage feed to the electronic throttle unit and then continues by suggesting that you check the battery and charging system. However, the battery's condition when the vehicle is in the workshop does not necessarily show the battery voltage when the malfunction was detected.

Instead, the best information is found in the frozen values, that is, voltage that the Engine control module (ECM) detects when Electronic throttle module (ETM) indicated the malfunction.

However, you should remember that this is not an indication of voltage feed to Electronic throttle module (ETM), it is voltage feed to Engine control module (ECM). If Engine control module (ECM) according to frozen values has had good voltage the battery was okay. Therefore, voltage feed to Electronic throttle module (ETM) should be checked separately.

Frozen values for ECM 903F

1. Condition, heated oxygen sensor control bank 1 = LR: Closed circuit with two sensors
2. Condition, heated oxygen sensor control bank 2 = LR: Closed circuit with two sensors
3. Calculated load = 4.71%
4. Engine temperature = 87 °C
5. Fuel adaption, quick adjustment, bank 1 = 15.63%
6. Fuel adaption, slow adjustment, bank 1 = -0.78%
7. Fuel adaption, quick adjustment, bank 2 = 23.44%
8. Fuel adaption, slow adjustment, bank 2 = -0.78%
9. Engine speed = 760 rpm
10. Vehicle speed = 0 km/h
11. Boost pressure = 30%
12. Battery voltage = 12.50 V
13. Throttle angle, desired value = 14.84%
14. Air mass = 23.8 kg/h
15. Outside temperature = 33 °C

In this case we assume that the vehicle had low battery voltage in the workshop. However, as can be seen in the frozen values, battery voltage was okay when the malfunction occurred, so this was probably not the cause.

This is an example of how frozen values can be used to increase efficiency of troubleshooting and avoid using too much time for incorrect troubleshooting. This prevents troubleshooting and fixing a malfunction that was not the real cause of the problem that was to be solved.

The odometer reading (km) is sometimes included in frozen values in Engine control module (ECM). This enables a quick comparison with the odometer so that you can assess if the malfunction occurred as part of the troubleshooting and can be ignored. For example, CAN-network-related diagnostic trouble codes are saved when the battery voltage drops during work on the vehicle since passenger compartment lighting and other loads drain the battery.

The frozen values indicate odometer reading in km. If you multiply this value by factor 0.62 you obtain driving distance in miles. Current driving distance in both miles and km can be read out with VIDA (Volvo scan tool).

Keep the following in mind when using frozen values for troubleshooting.

The frozen values to be used with care are those stored for the CAN-net and are related to diagnostic trouble codes for Electronic throttle module (ETM).

If Electronic throttle module (ETM) detects that communication to Engine control module (ECM) is interrupted, then malfunction flags will be generated in Electronic throttle module (ETM). These malfunction flags will be sent to Engine control module (ECM) first when communication on the CAN-net works again.

This means that Engine control module (ECM) will store the diagnostic trouble codes first when Electronic throttle module (ETM) delivers them, which in turn means that it is at this point in time that the frozen values are saved. For Electronic throttle module (ETM) this means that the frozen values will be from a point in time after the malfunction first occurred.

see DESIGN

READING OFF THE CONTROL MODULE IDENTIFICATION

VIDA identifies control modules by reading off a number of codes from the control module memory.

The codes contain information about the control module

1. hardware P/N (control module without software)
2. hardware serial number (control module without software)
3. software P/N
4. diagnostic software P/N.

SYSTEM OVERVIEW

see SYSTEM OVERVIEW

see DESIGN

see SYSTEM OVERVIEW

Scheme 7

Differential Electronic Module (DEM) is directly secured onto the clutch unit housing and together with the axial solenoid constitutes one unit. The axial solenoid controls the control valve.

The Differential Electronic Module (DEM) receives signals via the Controller Area Network (CAN) from

1. Engine Control Module (ECM)
2. Central Electronic Module (CEM)
3. Brake Control Module (BCM)
4. Driver Information Module (DIM).

Conducted by these signals, the Differential Electronic Module (DEM) determines how high the oil pressure to the clutch unit should be. The oil pressure to the clutch driven plates is decisive for how much torque can be transferred to the rear wheels.

Four-wheel drive does not function in the event of a fault in the Differential Electronic Module (DEM).

Scheme 8

The oil pressure and temperature sensor is fitted close to the axial solenoid in the Differential Electronic Module (DEM) housing. The sensor is flushed with hydraulic oil. The sensor measures the temperature and pressure (measurement range 0 - 4 MPa) of the hydraulic oil. The sensor sends a signal on temperature and pressure to the control module. The control module uses the signal to adapt the function of the system when the temperature of the oil and its subsequent viscosity is changed.

If the temperature of the oil exceeds 105 °C then the clutch is depressurized and four-wheel drive is disconnected. When the temperature falls below 101 °C the clutch is pressurized again. The pressure of the oil is limited to max. 10.3 MPa by the safety valve.

Four-wheel drive does not function in the event of any fault in the temperature sensor, and the function is significantly reduced in the event of a fault in the pressure sensor.

The oil pressure and temperature sensor can be diagnosed.

Scheme 9

The control valve/axial solenoid is located in the Differential Electronic Module (DEM) housing.

The control module supplies a variable pulse width modulated (PWM) signal to the axial solenoid. The solenoid changes the position of the control valve in accordance with the control signal. The pressure to the working piston of the clutch driven plates is controlled in this way.

Four-wheel drive does not function in the event of a fault in the control valve/axial solenoid.

The control valve/axial solenoid can be diagnosed.

Scheme 10

The electrical feed pump is fitted on the clutch unit and is supplied with voltage from the Differential Electronic Module (DEM). When the engine is started and reaches an engine speed of over 400 rpm the electrical feed pump is supplied with voltage from the control module.

The feed pump pumps oil to the axial pistons whose rollers are applied to the cam disc. At the same time oil flows to the working piston so that the play in the disc package is eliminated and the clutch's capacity for rapid reaction and control is prepared.

Four-wheel drive does not function in the event of a fault in the feed pump.

The feed pump can be diagnosed.

The control module can be identified by means of reading off a number of codes.

The codes contain information about the control module

1. hardware P/N (control module without software)
2. hardware serial number (control module without software)
3. software P/N
4. diagnostic software P/N

The control module can be identified by means of reading off a number of codes.

The codes contain information about the control module

1. hardware P/N (control module without software)
2. hardware serial number (control module without software)
3. software P/N
4. diagnostic software P/N.

The diagnostic tool identifies control modules by reading off a number of codes from the control module memory.

The codes contain information about the control module

1. hardware P/N (control module without software)
2. hardware serial number (control module without software)
3. software P/N
4. diagnostic software P/N.

The diagnostic tool identifies control modules by reading off a number of codes from the control module memory.

The codes contain information about the control module

1. hardware P/N (control module without software)
2. hardware serial number (control module without software)
3. software P/N
4. diagnostic software P/N.

DESCRIPTION OF THE SCROLLING VALUES (LAMPS)

Warning lamp seat belts, value

Indicates whether the lamp is on or off according to the control module.

SRS warning lamp, value

Indicates whether the lamp is on or off according to the control module.

Brake system warning lamp, value

The ABS control module lights or extinguishes the lamp via the control area network. The lamp may assume the value on or off.

Lamp parking brake warning, value

Indicates whether the lamp is on or off according to the control module.

Lamp low oil pressure, value

The oil pressure signal can be read off. The signal comes from the engine control module (ECM). One can read off whether the low oil pressure lamp should be on or off.

Charge lamp, value

Indicates whether the lamp is on or off according to the control module.

Indicator lamp fog lamp rear, value

Indicates whether the lamp is on or off according to the control module.

Malfunction indicator lamp (MIL), value

Indicates whether the lamp is on or off according to the control module.

ABS warning lamp, value

Indicates whether the lamp is on or off according to the control module.

Traction control warning lamp, value

The Brake Control Module (BCM) transmits the lamp signal to the driver information module (DIM) via the Control area network (CAN). Indicates whether the lamp is on or off according to the Driver Information Module (DIM).

Trailer warning lamp, value

Indicates whether the lamp is on or off according to the control module.

General orange warning lamp, value

Indicates whether the lamp is on or off according to the control module.

General red warning lamp, value

Indicates whether the lamp is on or off according to the control module.

High beam, value

Indicates whether the lamp is on or off according to the control module.

Lamp low fuel level, value

Indicates whether the lamp is on or off according to the control module.

DESCRIPTION OF THE SCROLLING VALUES (OTHER SIGNALS)

Fuel level, value

Signal from the two fuel level sensors in the rear electronic module (REM). The value displays between 0 and 80 liters depending on the amount of fuel in the tank.

Engine coolant temperature, value

An engine coolant temperature (ECT) display. The signal comes from the engine control module (ECM) and the temperature is displayed in Celsius.

Engine speed (RPM), value

An engine speed (RPM) display. The signal is between 0 and 8000 rpm and comes from the engine control module (ECM).

Vehicle speed, value

The vehicle speed can be read off. The signal comes from the Brake Control Module (BCM) or the transmission control module (TCM) via the Control area network (CAN).

Brake fluid level, value

The sensor is directly connected to the driver information module (DIM). Indicates whether the control module interprets the signal as low or high level.

Parking brake, value

The sensor is directly connected to the driver information module (DIM). Indicates whether the control module interprets the signal as activated or not activated. With the parking brake applied the sensor is activated.

The SRS indicator lamp status, value

The Driver Information Module (DIM) informs the Supplemental Restraint System Module (SRS) if the indicator lamp is working or is defective.

Cruise control, value

Indicates whether the cruise control status is on or off.

DESCRIPTION OF THE CUSTOMER PARAMETERS IN THE DRIVER INFORMATION MODULE (DIM)

Total mileage, value

Measurement range 0-999999 km, 0-999999 miles. The parameter can only be programmed once before the read off mileage exceeds 500 km or 310 miles. Programmed by the Central Electronic Module (CEM) after the control module has been replaced.

Distance conditions for service, value

Indicates the mileage required to display the service indicator message. The available values for metric calibrated instruments are 5000, 7500, 10000, 12000, 15000 or 20000 km. The available values for imperial calibrated instruments are 2500, 5000, 6000, 7500, 10000 or 12500 miles.

Time conditions for service, value

Indicates the time required to display the service indication message. The values set are 6, 12, 18 or 24 months.

Engine run time conditions for service, value

Indicates the time the engine must have been running before the service indication message will be displayed. The value set is 500, 750 or 1000 hours.

Displaying zeroes, value

Setting the instrument panel to display or not display the zeroes.

Temperature unit, value

The temperature unit of measurement can be selected. The temperature display can be selected between Celsius or Fahrenheit.

Unit trip computer, value

Setting the trip computer (applies only to cars with trip computer). It is possible to select liters, Imperial gallons or US gallons.

Clock position, value

12- or 24- hour display.

Mileage at service, value

Reading off the mileage at service. The parameter can be programmed between 0-999999 km or miles. When resetting the service reminder indicator (SRI) the parameter is reprogrammed by copying the mileage.

Time at service, value

Reading off global time at service. The parameter can be between 0 -163 months (13.6 years). When resetting the service reminder message, the parameter is reprogrammed by copying the global time in the central electronic module (CEM) to the driver information module (DIM).

Engine hours since service, value

Parameter read off. Indicates how many hours the engine has run since the last service. The parameter can be between 0 -65536 hours. Resets when service reminder message is reset.

Global time, value

Reading off the clock in the central electronic module (CEM). The parameter can be between 0 -163 months (13.6 years).

Parking brake warning

Setting the sound signal for the parking brake warning. Parking brake warning can be on or off. The default position is on.

DESCRIPTION OF COMPONENT / FUNCTION ACTIVATION

Lamps and displays

The combined instrument panel lamps flash and the gauges sweep from minimum to maximum for 4 seconds.

Warning lamp seat belts, value

Activating the instrument lamp.

SRS warning lamp, value

Activating the instrument lamp.

Brake system warning lamp, value

Activating the instrument lamp.

Lamp parking brake warning, value

Activating the instrument lamp.

Lamp low oil pressure, value

Activating the instrument lamp.

Charge lamp, value

Activating the instrument lamp.

Indicator lamp fog lamp rear, value

Activating the instrument lamp.

Malfunction indicator lamp (MIL), value

Activating the instrument lamp.

ABS warning lamp, value

Activating the instrument lamp.

Traction control warning lamp, value

Activating the instrument lamp.

Trailer warning lamp, value

Activating the instrument lamp.

General orange warning lamp, value

The orange triangular warning lamp in the center of the instrument panel is activated.

General red warning lamp, value

The red triangular warning lamp in the center of the instrument panel is activated.

High beam indicator lamp, value 1

Activating the instrument lamp.

Lamp low fuel level, value

Activating the instrument lamp.

OVERVIEW

The engine is an 8 cylinder V-engine with 60 degrees angle between the two cylinder banks. A specially adapted exhaust system together with the offset crankshaft pins gives the characteristic V8 sound. The engine is transverse and is only available in combination with AWD.

The engine is mounted vertically on the subframe.

Displacement is 4.4 dm 3 . Each cylinder has four valves.

The engine has a variable intake system which gives high torque at low engine speeds (rpm) and high performance at high engine speeds (rpm).

The ignition system has directly installed ignition coils.

The engine has mechanical valve lifters and electronic throttle. The throttle body is heated by coolant which means that pre-heating of intake air is not required.

The engine has double pairs of overhead camshafts, driven by three maintenance-free chains.

The engine has a counter rotating balancer shaft which gives vibration free running.

The cylinder block is made of a light metal alloy.

The direction of cooling system flow allows the coolant to first cool the cylinder heads and then the engine block.

All auxiliary units, the alternator, servo pump and A/C compressor are directly mounted on the engine block.

95 RON fuel can be used for normal operation. 98 RON is recommend for maximum performance and lowest possible fuel consumption. When driving in climates hotter than +38 °C, fuel with the highest possible octane rating is recommended to ensure the best possible performance and fuel consumption.

The engine is regulated by the Engine Control Module (ECM).

Scheme 11

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 (U bat ) 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 fusebox in the passenger compartment supplies current to the ignition switch.

The central electronic module (CEM) has diagnostics for the ignition switch.

General

The engine control module (ECM) diagnoses both internal signals and functions as well as signals and functions from connected components.

Conditions for diagnosis

For the diagnosis of a component or function to start, certain specific conditions must be met. The conditions for diagnostics vary depending on the component or function being diagnosed.

Conditions must be met during the diagnostic in order for the diagnostic to be completed. The time and conditions for the diagnostic vary depending on the component or function being diagnosed. Certain diagnostics only require the ignition to be switched on and off for a diagnostic to be run. Other diagnostics require that several different conditions are met. For example

1. vehicle speed
2. engine coolant temperature (ECT)
3. time since start
4. different load and engine speed relationships in the same trip
5. a certain event (for example the evaporative emission system (EVAP) valve is operating).

When the engine control module (ECM) has run all the implemented diagnostics, the control module has completed a "trip". An extensive driving schedule in various conditions is required to complete a trip. The engine may also need to be shut off for a certain amount of time and then switched on again to complete a trip.

Emissions related diagnostic functions

The engine control module (ECM) checks that the emissions related systems are working. These systems are checked by running a diagnostic function. The diagnostic function checks the components and that the system is functioning.

Diagnostic trouble code (DTC) memory

When the engine control module (ECM) detects a fault, the diagnostic trouble code and status are stored in the diagnostic trouble code memory and are visible during normal diagnostic trouble code readout. If the diagnostic trouble code (DTC) lights the malfunction indicator lamp (MIL), this occurs at the same time. If an existing fault disappears and does not recur, the engine control module changes the status of the diagnostic trouble code after a certain number of fault-free operating cycles (depending on the nature of the diagnostic trouble code). This means that it can no longer be read during normal diagnostic trouble code readout. In this status, the diagnostic trouble code remains until the engine control module (ECM) erases diagnostic trouble codes or is disconnected from power.

Substitute value

For certain types of diagnostic trouble codes (DTCs), the missing signal is replaced with a substitute value so that the system can continue functioning.

see SYSTEM OVERVIEW

Scheme 12

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 (U bat ) 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.

Scheme 13

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 a piston is approaching top dead center (TDC).

The signal from the engine speed (RPM) sensor is also used to check the engine for misfires. For further information, see: MISFIRE DIAGNOSTIC

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 signals from the camshaft position (CMP) sensor.

The engine speed (RPM) sensor can be diagnosed by the engine control module (ECM) and the sensor signal (engine speed (RPM)) can be read off.

Scheme 14

The function of the camshaft position (CMP) sensor is to detect the flanks of the camshaft rotor. The signal from the sensor is used by the engine control module (ECM) to determine the angle of the camshaft.

Each camshaft is divided into a number of flanks (segments) per camshaft revolution. A pulse wheel on the camshaft consisting of teeth (the teeth are positioned by each flank) is used by the camshaft position sensor (CMP) to detect the flanks and the position of the camshaft.

In the event of misfire or engine knock, the control module is able to determine which cylinder is misfiring or knocking using the camshaft position (CMP) sensor signal. Also, see KNOCK SENSOR (KS) and ENGINE SPEED (RPM) SENSOR .

Data about the camshaft position is used during camshaft control (CVVT). See: CAMSHAFT CONTROL (CVVT)

The sensor, which is a magnetic resistor with a permanent magnet, is grounded in the control module and supplied with 5 V from the control module. When one of the teeth on the camshaft pulse wheel passes the camshaft position (CMP) sensor, a signal is transmitted to the control module from the camshaft position (CMP) sensor. The signal varies between 0 - 5 V and is high when a tooth is close to the camshaft position (CMP) sensor and low when the tooth leaves the camshaft position (CMP) sensor.

There is camshaft position (CMP) sensor for each camshaft.

The camshaft position (CMP) sensors are located by the camshafts on the rear edge of the engine (left-hand side of the vehicle, closest to the flywheel).

The engine control module (ECM) can diagnose the camshaft position (CMP) sensors.

Scheme 15

The function of the knock sensor (KS) is to monitor combustion knocking from the engine. Knocking may damage the engine and reduces the efficiency of engine combustion.

If the engine control module (ECM) registers knocking from any of the cylinders, the ignition will be retarded for that cylinder at the next combustion stage. If repeated ignition retardation does not prevent knocking, the injection period will be increased. This has a cooling effect.

The sensor is made up of Piezo electrical crystals. If there is engine knock, vibrations (sound waves) spread through the cylinder block to the knock sensor (KS). The resultant mechanical stress in the Piezo electrical material in the knock sensors generates a voltage. This signal is transmitted to the engine control module (ECM). The signal corresponds to the frequency and amplitude of the sound waves. This allows the Engine Control Module (ECM) to determine if the engine is knocking. The camshaft position (CMP) sensor and engine speed (RPM) sensor are used to determine the operating cycle of the engine (which cylinder is igniting) and therefore which cylinder is knocking.

The knock sensors are located on the engine block between the cylinder rows.

Knock sensor 1 detects knock on cylinders 5, 6, 7 and 8. Knock sensor 2 detects knock on cylinders 1, 2, 3 and 4.

The engine control module (ECM) can diagnose the knock sensors (KS).

Scheme 16

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

1. the injection period
2. the idle speed
3. the engine cooling fan (FC)
4. the ignition advance
5. engagement and disengagement of the A/C compressor
6. 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 coolant temperature (ECT) can be diagnosed by the engine control module (ECM) and the value of the sensor can be read off.

Scheme 17

Overview

The mass air flow (MAF) sensor is a combined sensor and contains two sensors in the same component

1. mass air flow (MAF) sensor
2. intake air temperature (IAT) 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

1. the injection period
2. the fuel pressure
3. the ignition timing
4. 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 analog and varies between approximately between 0.5 - 4.5 V. Low air flow (low mass) results in low voltage, high air flow (high mass) gives high voltage.

The mass air flow (MAF) sensor can be diagnosed by the engine control module (ECM) and the sensor signal can be read off.

Intake air temperature (IAT) 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 intake air temperature. 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 temperature sensor can be diagnosed by the engine control module (ECM) and the sensor signal can be read off.

See: OVERVIEW

GENERAL

The engine control module (ECM) diagnoses both internal signals and functions as well as signals and functions from connected components.

GENERAL

The purpose of the generator (GEN) is to supply the power consumers with power and to ensure that the battery remains charged. The generator (GEN) is mounted on the front edge of the engine.

The power handling capacity of the generator (GEN) depends on the engine speed (RPM). When the engine is idling the generator (GEN) only supplies approximately half the maximum power handling capacity. When the engine is idling with many power consumers connected battery recharge is negatively affected i. e, the battery does not charge. Battery charging is less efficient in cold conditions than at room temperature. This means that when the engine is idling for a long time, with large power consumers connected the battery can drain.

If the generator fails to charge the power consuming components will take their supply exclusively from the battery. In the end this will drain the battery completely.

The generator (GEN) first generates AC current which is converted to DC current in the DC bridge. the generator (GEN) has a built-in charge regulator.

The auxiliaries belt transfers power from the crankshaft pulley to the auxiliaries such as the power steering pump, air conditioning (A/C) compressor and generator (GEN). The belt tension is tensioned using an automatic belt tensioner. The belt is a Poly-v-belt.

The generator (GEN) with charge regulator can be diagnosed through the central electronic module.