Ignition and Control Systems - Design and Function (Convertible): Diagnosis Volvo C70 I

Misfire diagnostic

If the fuel/air mixture does not ignite at the correct moment it can be said that the engine is misfiring. The flywheel is divided into 5 sector where every sector corresponds to a special cylinder. The engine control module (ECM) detects misfires by registering the time between two sectors of the flywheel.

The time between the two segments varies depending on

1. misfiring The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. By registering the time difference between the sectors and comparing this with the time differences in an earlier rotation misfires can be gauged. To eliminate mechanical tolerances one of the 5 sectors on the flywheel is used as a reference point for the timing.
2. driveline oscillations The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. By registering the time difference between the sectors and comparing this with the time differences in an earlier rotation misfires can be gauged. To eliminate mechanical tolerances one of the 5 sectors on the flywheel is used as a reference point for the timing.
3. normal variations caused by uneven combustion The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. By registering the time difference between the sectors and comparing this with the time differences in an earlier rotation misfires can be gauged. To eliminate mechanical tolerances one of the 5 sectors on the flywheel is used as a reference point for the timing.
4. flywheel mechanical tolerances The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. By registering the time difference between the sectors and comparing this with the time differences in an earlier rotation misfires can be gauged. To eliminate mechanical tolerances one of the 5 sectors on the flywheel is used as a reference point for the timing.

Misfire diagnostics are also shut off when

1. A diagnostic trouble code is stored for the engine speed /position sensor, mass air flow (MAF) sensor, engine coolant temperature sensor, camshaft position (CMP) sensor or ABS. The ABS module continuously sends out the largest differences between the wheel sensor signals on the network, approximately 50 times per second. Using these values the engine control module (ECM) can determine if any misfiring is due to the nature of the road or if there are genuine interruptions in the engine control module. Because of this the accelerometer is not required. The speed signal from the ABS module is used instead.
2. there are drive line oscillations, caused by uneven road surfaces for example, which may lead to uneven engine operation. The ABS module continuously sends out the largest differences between the wheel sensor signals on the network, approximately 50 times per second. Using these values the engine control module (ECM) can determine if any misfiring is due to the nature of the road or if there are genuine interruptions in the engine control module. Because of this the accelerometer is not required. The speed signal from the ABS module is used instead.

Lit/flashing malfunction indicator lamp (MIL)

Misfiring lights the malfunction indicator lamp (MIL). In the event of misfiring, if there is risk of damage to the three way catalytic converter, the malfunction indicator lamp (MIL) will flash and then switch to a constant light.

The engine control module (ECM) registers and stores the rpm and load range in which it occurred. The malfunction indicator lamp (MIL) lights up if the misfire diagnostic trouble code (DTC) is stored during the previous driving cycle and a new code for misfiring is stored in the second driving cycle.

If the event the misfiring stopping, the requirements for the rpm and load parameters must be met before the engine control module (ECM) will begin counting down to extinguish the warning lamp and extinguish stored diagnostic trouble codes (DTCs) for misfiring.

Scheme 90

The Electronic throttle system is an electronically controlled throttle system which consists of an electronic throttle module and accelerator pedal (AP) position sensor. The system has no mechanical links or cables.

Diagnostics

In order for the engine control module (ECM) or electronic throttle module to start using the correct signals, after having detected a temporary or intermittent fault in the system, the ignition must be switched off and then the engine started again so that.

Scheme 91

New sensors and functions which are different to previously known principles are marked with bold text .

Scheme 92

Sensors and functions which are different to previous types are marked in bold text .

Leak diagnostic

Vapor which evaporates from the fuel in the fuel tank is routed to and stored in the EVAP canister from where it is introduced into the combustion process via the canister purge (CP) valve and negative pressure in the intake manifold.

A leak diagnostic has been introduced in certain markets to ensure that there are no leaks in the fuel tank system. The diagnostic is designed to detect leakage corresponding to a 1 mm or larger hole.

The fuel tank system consists of fuel tank, fuel filler pipe, EVAP canister, canister purge (CP) valve and all pipes between these components. To be able to diagnose the fuel tank system, it is also equipped with fuel tank pressure sensor and EVAP canister shut-off valve.

Leak diagnostic different stages

The diagnostic is divided into different phases in which the various components are tested. If a fault is detected in any of the phases the diagnostic is interrupted and the diagnostic trouble code (DTC) for the component identified is stored. Diagnosis is carried out in the following stages

1. The fuel tank pressure is checked so that it is stable and is not too low. Too low pressure means blocked EVAP canister shut-off valve or leaking canister purge (CP) valve and a diagnostic trouble code (DTC) is stored.
2. EVAP canister shut-off valve is shut and an evaporation check is carried out by gauging how much fuel tank pressure increases. This provides a value for how much fuel evaporates, and this value is used later to calculate leakage flow. If fuel tank pressure sinks, this indicates that the canister purge (CP) valve is leaking and diagnostic trouble code (DTC) for an open canister purge (CP) valve is stored.
3. The canister purge (CP) valve is pulsed and because of the negative pressure in the intake manifold the engine starts to suck air through the EVAP canister. The canister purge (CP) valve pulses with a 24% duty cycle. The pressure in the tank then falls to +/- 1.5 kPa. If this pressure is not reached within 25 seconds it indicates a larger leak in the fuel tank. and the diagnostic trouble code (DTC) for a large leak is stored.
4. The canister purge (CP) valve is closed and the EVAP canister shut-off valve is still closed and there is negative pressure in the fuel tank. This negative pressure will decrease slowly, the decrease rate depends on fuel level, tank deformation, fuel evaporation and any leaks. EVAP canister shut-off valve opens and the time taken to return to ambient pressure is measured. Too long time it means that the EVAP canister shut-off valve blocked. By compensating for evaporation which is measured in step 2 it can calculate a leak. If the calculated leakage flow exceeds a certain level this indicates a smaller leakage in the fuel tank system and diagnostic trouble code for small leak is stored.
5. The diagnostic test is completed.

During the different phases when the system gauges whether the fuel tank system pressure acts normally or not, there are a number of circumstances which are taken account of, for example

1. the amount of fuel in the tank
2. height above sea level
3. fuel temperature and evaporation

The system can calculate this information. Therefore it is not possible to describe how quickly or how much the pressure is permitted to increase or fall in the different phases.

To carry out the diagnostic it is necessary that

1. there are no diagnostic trouble codes (DTCs) for the canister purge (CP) valve, EVAP canister shut-off valve, fuel tank pressure sensor, manifold absolute pressure sensor (MAP) and mass air flow sensor
2. fuel trim should be active when the canister purge (CP) valve is opened
3. The speed is between 29 and 110 km/h (18 - 68 mph)
4. the car is below 2500 meters above sea level
5. outside temperature must be above -8°C (17.6°F)
6. engine coolant temperature (ECT) must be above -8°C (17.6°F) and below 120°C (248°F)
7. the concentration of fuel fumes in the EVAP canister must not be too high

The diagnostic test starts at the earliest 14 minutes after the engine has started when all conditions have been fulfilled, and takes approximately 60-80 seconds.

If the diagnostic is interrupted for any reason, it will try to start again the next time all conditions are met. The engine control module (ECM) performs a maximum of 10 diagnostic attempts during an operating cycle. If no fault is detected the diagnostic will not run again in the same operating cycle. If a fault is detected two further attempts are made to evaluate the fault.

Scheme 93

DENSO EMS is a new engine control system located on all B52X4S engines from and including 1999 model year. The system is largely similar to Motronic 4.4 in terms of the sensors and their functions.

The biggest new feature is the communication between the ECM and other modules, which occurs via a data network.

The system has other new features

1. ETS (Electronic Throttle System) that includes ETM (Electronic Throttle Module) and APM (Accelerator Pedal Module)
2. AACV (Air Assisted Control Valve)

The following communicate by ECM via the network

1. TCM (Transmission Control Module)
2. ETM (Electronic Throttle Module)
3. ABS (Antilock Braking System)
4. CDM (Can and Driver information Module)
5. DLC (Diagnostic Link Connector)

DENSO contains a large number of sensors which function according to known principles and send information by analog signals directly to the ECM.

As applies to output signals and controlled components these also function to known principles, with a few exceptions. These exceptions are covered on the following pages.

For more information about the electronic throttle unit system and related components such as the throttle unit, accelerator pedal sensor, stop lamp switch, clutch pedal sensor switch and brake pedal position sensor, see Design and Function .

Scheme 94

The three-way catalytic converter (TWC) stores oxygen found in the exhaust gases and uses it to make toxic gases more environmentally friendly. The catalytic converter is a three-way catalytic converter (TWC) in which HC (hydrocarbons) and CO (carbon monoxide) are oxidized and NO X (nitrogen oxides) are reduced. As the three-way catalytic converter (TWC) ages its ability to store oxygen drops. This reduces the conversion capacity of the three-way catalytic converter (TWC). To avoid dangerous emissions the engine control module (ECM) checks three-way catalytic converter (TWC) efficiency. This check is carried out as follows.

Two heated oxygen sensors (HO2S) are used to check the catalytic converter one upstream and one downstream of the catalytic converter. The main function of the heated oxygen sensors (HO2S) is to measure the oxygen content in the exhaust gases so that the engine control module (ECM) can maintain the fuel/air mixture at around lambda=1. This mixture provides optimum three-way catalytic converter (TWC) efficiency. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared (amplitude is a measure of signal oscillation).

When three-way catalytic converter (TWC) efficiency is good and the fuel/air mixture is normal, the front heated oxygen sensor (HO2S) signal switches between rich and lean (large amplitude) while the rear heated oxygen sensor (HO2S) signal is even (small amplitude). When three-way catalytic converter (TWC) efficiency is poor and the fuel/air mixture is normal, the rear heated oxygen sensor (HO2S) signal switches between rich and lean (large amplitude) because the exhaust gases are passing straight through the three-way catalytic converter (TWC) without being converted

If rear sensor amplitude becomes too great in relation to the front sensor signal for a number of diagnostic tests, diagnostic trouble code (DTC) EFI-443 Catalytic converter efficiency will be stored.

Heated oxygen sensor (HO2S) diagnostic

Two heated oxygen sensors (HO2S) are used in the Motronic 4.4. The heated oxygen sensors (HO2S) are checked for open and short-circuits as usual. If either of these faults occurs, diagnostic trouble code (DTC) EFI-212 (front heated oxygen sensor (HO2S)) or EFI-153 (rear heated oxygen sensor (HO2S)) are stored. In addition, the signal from the front heated oxygen sensor (HO2S) is checked. This check is carried out as follows.

The engine control module (ECM) receives exhaust composition data from the front heated oxygen sensor (HO2S). Using this information the engine control module (ECM) calculates injection period. Because the front sensor is located upstream of the three-way catalytic converter (TWC) it is subject to attack by the uncleaned exhaust gases. This leads to the sensor ageing and its signal changing

These changes are monitored by checking

1. front heated oxygen sensor (HO2S) mean signal voltage
2. rear heated oxygen sensor (HO2S) control
3. front heated oxygen sensor (HO2S) period.

To determine front heated oxygen sensor (HO2S) mean voltage the engine control module (ECM) uses the rear heated oxygen sensor (HO2S) signal. This signal provides information about the exhaust gas oxygen composition downstream of the catalytic converter. The engine control module (ECM) can use this information to take account of front sensor ageing in its injection period computations.

The mean rear sensor signal voltage should be approximately 0.6 V when twin heated oxygen sensor (HO2S) control is active. First the injection period is calculated on the basis of the front sensor signal. Then the mean rear sensor signal is calculated. If it is not 0.6 V the injection period calculations are adjusted so that the correct mean rear sensor signal will be achieved. When this adjustment exceeds a certain limit for a number of diagnostic tests, diagnostic trouble code (DTC) EFI-436, rear heated oxygen sensor (HO2S) compensation, is stored.

When the engine is running the adjustment carried out by the rear heated oxygen sensor (HO2S) should be positive and negative, if not diagnostic trouble code (DTC) EFI-425, rear heated oxygen sensor (HO2S), control, will be stored.

Twin heated oxygen sensor (HO2S) control starts and remains active when

1. the front heated oxygen sensor (HO2S) has started control
2. the rear heated oxygen sensor (HO2S) has reached operating temperature
3. catalytic converter temperature exceeds 112°C (calculated by the engine control module (ECM))
4. engine speed (RPM) is between 1500-2300 rpm
5. load is 1.2-3.0 ms (at 1.000 rpm), 1.6-3.0 ms (at 2.000 rpm).

Twin heated oxygen sensor (HO2S) control is suspended during fuel shut-off, if the engine control module (ECM) detects misfiring (diagnostic trouble codes (DTCs) EFI-45X, EFI-543, EFI-545, EFI-55X) or if the engine control module (ECM) detects a fault in

1. The EVAP system (diagnostic trouble code (DTC) EFI-315)
2. three-way catalytic converter (TWC) (diagnostic trouble code (DTC) EFI-443)
3. heated oxygen sensor (HO2S) preheating (diagnostic trouble code (DTC) EFI-521 or EFI-522)
4. mass air flow (MAF) sensor (diagnostic trouble code (DTC) EFI-121).

A defective sensor may also have the correct mean signal voltage. For this reason the front sensor period is also monitored. The engine control module (ECM) monitors how long it takes for the front heated oxygen sensor (HO2S) to switch from rich to lean to rich again. This is carried out at part load, when the difference between a good and bad sensor is greatest. When the period becomes too long for a number of diagnostic tests, diagnostic trouble code (DTC) EFI-435 Front heated oxygen sensor (HO2S) slow response, is stored.

Scheme 95

The atmospheric pressure sensor supplies the engine control module (ECM) with a signal describing air pressure. It provides the engine control module (ECM) with the car's height above sea level.

Atmospheric pressure sensor acts on the control of

1. boost pressure at high altitude
2. injection time when starting at high altitude.

At heights above 2400 meters the following are disabled

1. leak diagnostic
2. pulsed secondary air injection (PAIR) diagnostic
3. mass air flow (MAF) sensor, faulty signal.

The atmospheric pressure sensor contains a piezo-electric crystal in the shape of a diaphragm. One side of this diaphragm is subject to atmospheric pressure, to other side is acted on by a contained gas. The deformation of the piezo-electric diaphragm, and therefore its resistance is proportional to air pressure.

The voltage across the sensor is a function of air pressure and, therefore, of sensor resistance.

Voltage can vary between 0V and 5V.

The sensor is supplied with a stabilized voltage of 5V from the engine control module (ECM).

If the signal from the atmospheric pressure sensor is faulty or missing the engine control module (ECM) adopts a substitute value.

The atmospheric pressure sensor is located by the right hood catch.

Scheme 96

The function of the two knock sensors (KS) is to provide the engine control module (ECM) with signals to determine whether the engine is knocking.

The engine control module (ECM) uses the knock sensor (KS) and camshaft position (CMP) sensor signals to identify the cylinder in which knock is present.

The engine management system incorporates two knock sensor (KS), each of which consists of the following components

1. housing
2. sleeve
3. piezo-electric crystal
4. contact strips
5. damping weight
6. washer
7. nut

Engine knock produces vibrations which are transmitted through the block. The piezo-electric crystal reacts to these by transmitting a signal (a function of sound wave frequency and amplitude) to the engine control module (ECM).

The front knock sensor (KS) detects knocking in cylinders 1, 2 and 3. The rear knock sensor (KS) detects knocking in cylinders 4 and 5.

The knock sensors (KS) are mounted on the cylinder block.

Scheme 97

The outside temperature sensor supplies the engine control module (ECM) with a signal describing the outside temperature.

This signal is used to disable certain diagnostic functions when the temperature is under 7°C.

The following diagnostic functions are disabled

1. leak diagnostic
2. pulsed secondary air injection (PAIR) system diagnostic
3. misfire diagnostic
4. boost pressure control diagnostic.
5. mass air flow (MAF) sensor, faulty signal.

The sensor incorporates a temperature-sensitive resistance with a negative temperature coefficient (NTC). The sensor is supplied with a stabilized voltage of 5V. The voltage across the sensor is a function of the outside temperature and, therefore, of sensor resistance. Voltage can be between 0 V and 5 V.

If the signal from the outside temperature sensor is faulty or missing the engine control module (ECM) adopts substitute values.

The outside temperature sensor is located under the bumper on the left-hand side.

Scheme 98

The A/C relay (2/22) is activated if the A/C switch is pressed, the blower fan is operating and the engine control module (ECM) confirms it. Power is supplied to the A/C compressor solenoid clutch (8/3) and the cycling of the compressor can be controlled by the pressure switch (Pressostat) (7/53) normally.

In the following circumstances the compressor is disengaged to prevent it operating when full power is required, or when there is a risk of overheating

1. full acceleration; at wide open throttle (WOT) the engine control module (ECM) shuts the compressor down for a maximum of 15 seconds and a minimum of 3 seconds
2. risk of overheating. If coolant temperature is above approximately 125°C the air conditioning (A/C) compressor is prevented from operating in order to reduce engine load and avoid further overheating.
3. if pressure exceeds approximately 3000 kPa.

The engine control module (ECM) also prevents the compressor from engaging before the engine has started properly. The air conditioning (A/C) compressor cannot start until the engine has been started for approximately 5-15 seconds.

Scheme 99

The engine control module (ECM) (1) calculates engine speed based on signals from the engine speed (RPM) sensor (2). Engine speed (RPM) information is used for engine management. The engine control module (ECM) then sends a signal to the tachometer in the combined instrument panel (3) which provides the driver with information about engine speed.

Catalytic converter diagnostic

The three-way catalytic converter (TWC) stores oxygen found in the exhaust gases and uses it to make toxic gases more environmentally friendly. The catalytic converter is a three-way catalytic converter (TWC) in which HC (hydrocarbons) and CO (carbon monoxide) are oxidized and NOx (nitrous oxide) is reduced. As the three-way catalytic converter (TWC) ages its ability to store oxygen drops. This reduces the conversion capacity of the three-way catalytic converter (TWC). To avoid dangerous emissions the engine control module (ECM) checks three-way catalytic converter (TWC) efficiency. In brief, this check is carried out as follows.

Two heated oxygen sensors (HO2S) are used to check the catalytic converter; one upstream and one downstream of the catalytic converter. The main function of the heated oxygen sensors (HO2S) is to measure the oxygen content in the exhaust gases so that the engine control module (ECM) can maintain the engine fuel/air mixture at around lambda=1.

The catalytic converter diagnostic consists of two checks. The first checks how quickly the three-way catalytic converter (TWC) begins to operate, and the second is a response time check. When starting cold the control module checks how quickly the three-way catalytic converter (TWC) begins to operate. If the target lambda is already varying during this check, the following check is not carried out.

When the engine is at operating temperature, lambda variations are created (Dither function) by the diagnostic, adding a deviation to the target lambda signal which the fuel control system regulates towards. The deviation changes between positive and negative values so that the fuel/air mixture changes between rich and lean. The discharge through the three-way catalytic converter (TWC) is determined by studying the variation of lambda and the response from the rear probe.

On a poorly performing three-way catalytic converter (TWC), the deviation changes can easily be calculated by the rear probe response time. On an efficient three-way catalytic converter (TWC) this is more difficult, because the variations take too long to go through.

Two heated oxygen sensors (HO2S) are used in the Denso engine control module (ECM). The heated oxygen sensors (HO2S) are checked as usual for short-circuits and open-circuits. Diagnostic trouble code (DTC) ECM-2120 (front heated oxygen sensor (HO2S)) or ECM-2200 (rear heated oxygen sensor (HO2S)) will be stored if any of these faults occur. The probe heat elements are also checked. In the event of a fault, diagnostic trouble code (DTC) ECM-2110 (front heated oxygen sensor (HO2S), heating), ECM-2120 (front heated oxygen sensor (HO2S), probe control) or ECM-2210 (rear heated oxygen sensor (HO2S), heating) will be stored. In addition, probe control is also checked. In brief, these checks are carried out as follows.

The front heated oxygen sensor (HO2S)

The front heated oxygen sensor (HO2S), which is a linear type: Two checks where the switch over time between rich-lean and lean rich fuel/air mixture is checked. The diagnostic checks the response time of the front heated oxygen sensor (HO2S) when fuel shut-off is activated and deactivated.

The rich-lean check takes place when the fuel shut-off system is activated, on condition that the sensor current is below a lower limit (indicates rich fuel/air mixture). When the fuel shut-off system is activated, the sensor current usually rises (this indicates a lean fuel/air mixture). The lean-rich check measures the time taken for the sensor current to rise from a lower to an upper limit value. If the time counter exceeds a fault level without the sensor current having reached the upper limit value, the response is considered to be too slow; a fault marker is stored.

The lean-rich check is carried out in a similar way when the fuel shut-off system is deactivated. The difference is that the time taken for the sensor current to fall is measured. Diagnostic trouble code (DTC) ECM-210A (front heated oxygen sensor (HO2S)) is stored in the event of a fault in both of these checks.

In addition, the lambda value is also checked. This value must not deviate significantly from its control value. Diagnostic trouble code (DTC) ECM-210F (front heated oxygen sensor (HO2S)) is stored if the difference is too great.

Rear heated oxygen sensor (HO2S)

The rear heated oxygen sensor (HO2S), which is a binary type, is checked in the following way.

The control module checks the difference between the rear probe voltage maximum and minimum values. This voltage must not exceed 0.5 V. If the difference is greater, the control module takes an initialization value as its starting point. This is a maximum of 0 V and a minimum of 5 V. After this, the rear heated oxygen sensor (HO2S) maximum value must exceed the initialization value (0 V) for the probe voltage by at least 0.6 V and fall below the initialization value (5 V) probe voltage to the minimum value 0.1 V. If these limit values are not reached within approximately 5 minutes and the accumulated and actual probe warming has not reached certain limit values, the control module interprets it as a fault.

Twin probe control starts and is active when

1. the front probe has started control
2. the rear probe has reached operating temperature

Twin probe control is interrupted during fuel shut-off, during misfiring or in the event of a fault in

1. the catalytic converter
2. heated oxygen sensor (HO2S) heating

Leak diagnostics

Overview

Vapor which evaporates from the fuel in the fuel tank is routed to and stored in the EVAP canister from where it is guided into the combustion process via the canister purge (CP) valve and negative pressure in the intake manifold. The diagnosis is designed to detect leaks between 0.5-1 mm, depending on the model year.

The tank system consists of the fuel tank, fuel tank filler cap, fuel filler pipe, roll-over valve, EVAP canister, EVAP components, fuel tank pressure sensor, and EVAP canister shut-off valve.

The diagnostic is divided into different phases under which the various components are tested and faulty components are isolated with a diagnostic trouble code (DTC).

Conditions for diagnosis

The diagnosis begins when all the following conditions are met.

There must be no diagnostic trouble code (DTC) stored for the following components or functions

1. EVAP canister shut-off valve
2. the fuel tank pressure sensor
3. the canister purge (CP) valve
4. Vehicle speed is between 30-160 km/h, must be steady driving
5. Engine speed below 3500 rpm
6. Engine coolant temperature (ECT)> 60°C
7. Maximum altitude of 2500 meters above sea level
8. Outside temperature above +3.5°C
9. Stable fuel tank pressure
10. Low volume in the canister.

The diagnostic test works as follows

1. 1. The canister purge (CP) valve (C) closes the fuel tank ventilation. The EVAP canister shut-off valve is still open. The pressure in the tank must now return to atmospheric pressure. If the pressure in the fuel tank does not return to atmospheric pressure, the canister purge (CP) valve (C) is leaking or that the EVAP canister shut-off valve (B) is blocked. Diagnostic trouble code (DTC) ECM-4047 canister purge (CP) valve leaking or EVAP canister shut-off valve blocked is stored
2. 2. The evaporative emission system (EVAP) valve (C) is closed and the EVAP canister shut-off valve (B) closes the opening for fresh air ventilation. The pressure in the fuel tank must be unchanged or rise. If the fuel tank pressure drops the canister purge (CP) valve is leaking. Diagnostic Trouble Code (DTC) ECM-4047, canister purge (CP) valve leaking is stored. If the pressure in the fuel tank rises, there is considerable fuel evaporation and the diagnostic is cancelled
3. 3-4. The EVAP canister shut-off valve (B) remains closed, the evaporative emission system (EVAP) valve (C) starts to pulse. The pressure (A) in the fuel tank now starts to drop quite quickly. If the pressure does not drop quickly there is a major leak in the system. Diagnostic trouble code (DTC) ECM-4308 leak diagnostic major leak is then stored. If the pressure drops too quickly instead, the fuel tank level is too high and the diagnostic is cancelled
4. 5-6-7 The canister purge (CP) valve (C) closes. The EVAP canister shut-off valve (B) remains closed. When the fuel tank pressure has stabilized, a check is carried out as to whether pressure is rising too quickly in the fuel tank. This would indicate a minor leak in the fuel tank system and ECM-4308 Minor leak would be stored
5. 8-9-10. The evaporative emission system (EVAP) valve (C) pulses, so that the fuel tank pressure (A) drops again. The EVAP canister shut-off valve (B) then opens so that the fuel tank pressure can return to atmospheric pressure. Diagnostic trouble code (DTC) ECM-4047 EVAP canister shut-off valve blocked is stored if the recovery time is too long. The time taken to return to atmospheric pressure is also a measurement of the amount of fuel in the tank. The fuel level is used as a compensation value when calculating the size of the leak during stages 5-6-7 above.

The diagnostic test starts at the earliest 13 minutes after the engine has started when all conditions have been fulfilled, and takes approximately 60-80 seconds. If the diagnostic is interrupted it will try again when all the conditions have been fulfilled again. The control module makes a maximum of 20 attempts in one trip. No more attempts are made until the engine is started again.

Scheme 100

Shutting off the misfire diagnostic

Misfire diagnostics are shut off in the event of

1. driveline oscillations. Drive line oscillations, caused by uneven road surfaces for example, may lead to uneven engine operation. Drive line oscillations will be posted by the ABS system and this information is sent to the engine control module (ECM). The engine control module (ECM) uses this information in order to differentiate between oscillations and actual misfiring and the diagnostic is shut off.
2. diagnostic trouble codes (DTCs) in the flywheel sensor, mass air flow (MAF) sensor, ABS and camshaft position (CMP) sensor.

Throttle diagnostic

For more information about the electronic throttle unit system and related components such as the throttle unit, accelerator pedal sensor, stop lamp switch, clutch pedal sensor switch and brake pedal position sensor, see Design and Function .

Leak diagnostics (certain markets only)

To minimize false detection of leakage, new software has been released for the Engine control module (ECM). The software has been released afterwards, in order of priority, started at the end of 2006.

To check the current software version, see Vehicle communication in VIDA.

The improved software version makes diagnostics more robust and durable against aging and wear of the leak diagnostic unit. It affects strategies, behavior and to a degree also read off parameters.

1. Original version for model year -2004, see: «Leak diagnostics, original version (-2004)»(ref-404036-S37361134952011061000000)
2. Original version for model year 2005-, see: «Leak diagnostics, original version (2005-)»(ref-404036-S11878789202011061000000)
3. Improved version for all model years, see: «Leak diagnostics, improved version (2002-)»(ref-404036-S37018574092011061000000)

Scheme 101

All gases that evaporate from fuel in the fuel tank must be led to and stored in the evaporative emission system (EVAP) canister so that they can be directed into the engine for combustion. In order to detect leakages which cause evaporation of gases into the air, the fuel tank system is diagnosed for leakage. The fuel tank system consists of

1. fuel tank
2. the EVAP canister purge valve (1)
3. EVAP canister (2)
4. leak diagnostic unit (3)
5. air cleaner (ACL) (4)
6. Roll-over valve (5)
7. Float Limit Vent Valve (6)
8. fuel filler pipe (7)
9. all lines between the above components.

The fuel tank system has a leak diagnostic unit to diagnose any leakage. The leak diagnostic unit pressurizes the fuel tank system when the ignition is off, if the conditions for diagnosis have been met. The control module can detect faults in the function of the leak diagnostic unit and leakage that is 0.5 mm or greater. Minor leak; leakage greater than 0.5 mm but less than 1.0 mm. Major leak; leakage greater than 1.0 mm.

The leak diagnostic unit consists of a pump and a valve that controls the air flow in the unit. The fuel tank system tests for leaks by measuring the power consumption of the pump. The power consumption of the pump corresponds to a certain pressure in the fuel tank system. During diagnosis, the rate at which the pressure can build up is checked, taking into account the quantity of fuel in the tank. The quicker the pressurization the better the fuel tank system is sealed.

Conditions for diagnosis

The diagnosis begins when all the following conditions are met

1. There must be no diagnostic trouble code (DTC) stored for the following components or functions: the power stage for the pump in the leak diagnostic unit the power stage for the valve in the leak diagnostic unit the power stage for the EVAP canister purge valve the evaporative emission system (EVAP) valve the engine coolant temperature (ECT) sensor speed signal.
2. The engine is switched off until the engine coolant temperature (ECT) has fallen to a few degrees above the outside temperature, then engine running for at least 10 minutes
3. Ignition off
4. Vehicle speed 0 km/h
5. Engine coolant temperature (ECT) -5°C or higher
6. Maximum altitude of 2500 meters above sea level.
7. Outside temperature between -5 and +35°C
8. Fuel volume in the tank less than 85%. The engine control module (ECM) ignores these parameters if a diagnostic trouble code (DTC) is stored for the fuel level sensor and the fuel volume cannot be determined
9. Battery voltage between 11.0-14.5 V. The voltage must be stable
10. EVAP canister purge valve closed
11. Low volume in the canister.

Fuel tank filler cap check

The exception from the above conditions is when the car has been refuelled. The engine control module (ECM) starts a check of the fuel tank filler cap after refuelling. This check is a simplified version of the leak diagnostic unit for major leaks. The fuel tank filler cap control is run whilst the vehicle is being driven. This allows the control module to check that the cap has been reinstalled. A diagnostic trouble code (DTC) is stored in the engine control module (ECM) and a text message is displayed in the driver information module (DIM) if the cap is missing.

Diagnostic phases

The diagnostic is divided into the following phases and is carried out in sequence when all conditions for the diagnostic have been met.

1. Reference phase
2. Function test
3. Leak diagnostics

Reference phase (1-2)

Scheme 102

The illustration is a diagram of a fault free fuel tank system.

Before the leak diagnostic begins, the control module runs a reference phase for leakage. During the reference phase (1-2) for leakage that is 0.5 mm, the pump in the leak diagnostic unit pumps ambient air through a 0.5 mm hole and back out to the ambient air. At the same time, the power consumption (A) of the pump is measured and stored in the control module. The stored value (A) for the power consumption of the pump corresponds to a leakage of 0.5 mm. This value is then used by the engine control module (ECM) to determine the leak status of the fuel tank system.

Function test (1-3)

If the value for the power consumption of the pump is too high or low during the reference phase (1-2), or if the value varies too much during the reference phase (1-2), the diagnostic is cancelled and starts again the next time the conditions for the diagnostic are met. A diagnostic trouble code (DTC) is stored if the diagnostic is cancelled several time in a row because the power consumption of the pump is varying excessively.

After the reference phase, the valve (2) in the leak diagnostic unit is activated and controls the air flow to the fuel tank to pressurize the fuel tank system. This change of air flow will cause the power consumption of the pump to fall briefly before the pressure builds up in the fuel tank system (3). A diagnostic trouble code is stored if the value for the power consumption of the pump drops too quickly, slowly or not at all.

Leak diagnostic, major leak (leakage greater than 1.0 mm)

Scheme 103

The diagnostic for "major leaks" is carried out each time when the conditions for the diagnostic are met. The leak diagnostic unit pressurizes the fuel tank system, measures the power consumption of the pump (4) and compares this with a calculated desired value (B). A diagnostic trouble code (DTC) for a major leak is stored if the measured value does not reach the calculated desired value within a certain time (the time is determined by atmospheric pressure and the fuel level in the tank).

Leak diagnostic, minor leak (leakage greater than 0.5 mm but less than 1.0 mm)

The diagnostic for minor leaks is run every other time that the conditions for the diagnostic are met. The diagnostic for major leaks is always run before the diagnostic for minor leaks. The leak diagnostic unit continues to pressurize the fuel tank system (5-6). After a certain amount of time (the time varies depending on the fuel level in the tank), the engine control module (ECM) checks that the fuel tank system for leaks. This is determined based on

1. time
2. the measured reference current consumption of the pump (A)
3. the measured power consumption of the pump when the assessment is made
4. the shape and character of the current curve during pressurization.

A diagnostic trouble code (DTC) is stored if a minor leak is detected.

Scheme 104

All gases that evaporate from fuel in the fuel tank must be led to and stored in the evaporative emission system (EVAP) canister so that they can be directed into the engine for combustion. In order to detect leakages which cause evaporation of gases into the air, the fuel tank system is diagnosed for leakage. The fuel tank system consists of

1. fuel tank
2. the EVAP canister purge valve (1)
3. EVAP canister (2)
4. leak diagnostic unit (3)
5. air cleaner (ACL) (4)
6. Roll-over valve (5)
7. Float Limit Vent Valve (6)
8. fuel filler pipe (7)
9. all lines between the above components.

The fuel tank system has a leak diagnostic unit to diagnose any leakage. The leak diagnostic unit pressurizes the fuel tank system when the conditions for leak diagnostics are met.

The control module can detect faults in the function of the leak diagnostic unit and leakage that is 0.5 mm or greater. Minor leak; leakage greater than 0.5 mm but less than 1.0 mm. Major leak; leakage greater than 1.0 mm.

The leak diagnostic unit consists of a pump and a valve that controls the air flow in the unit. The Engine control module (ECM) checks for leakage in the fuel tank system by measuring the relationship between reached pressure and flow from the leak diagnostic pump during pressurization.

If a certain pressure is not reached with a predetermined supplied flow (with known mass), the Engine control module (ECM) interprets this as a leak from the fuel tank system.

Leak diagnostics starts in normal operation when specific conditions are met, see below. The diagnostics can also be started on command using VIDA when some of these conditions are ignored.

Conditions for diagnosis

The diagnosis begins when all the following conditions are met.

Note: When diagnostics are started on command using VIDA, certain different conditions apply. See relevant information about these, available with starting Quick test fuel tank system.

1. No diagnostic trouble codes (DTCs) for EVAP valve or atmospheric pressure sensor may be stored.
2. The engine is switched off until the engine coolant temperature (ECT) has fallen to a few degrees above the outside temperature, then engine running for at least 10 minutes
3. Ignition off
4. Vehicle speed 0 km/h.
5. Engine coolant temperature (ECT) 4-35°C.
6. Maximum altitude of 2500 meters above sea level
7. Outside temperature 4-35°C.
8. Fuel volume in the tank between 0-85%. The engine control module (ECM) ignores these parameters if a diagnostic trouble code (DTC) is stored for the fuel level sensor and the fuel volume cannot be determined.
9. Battery voltage between 11-15 V. The voltage must be stable.
10. EVAP canister purge valve closed
11. Low volume in the canister.
12. Fuel tank filler cap locked. Tip. Locking occurs when the vehicle speed exceeds approximately 20 km/h.

Diagnostic phases

The diagnostic is divided into the following phases and is carried out in sequence when all conditions for the diagnostic have been met.

1. reference phase
2. function test
3. checking the fuel tank system

Reference phase

Before the leak diagnostic begins, the control module runs a reference phase for leakage. During the reference phases for leakage that is 0.5 mm, the pump in the leak diagnostic unit pumps ambient air through a 0.5 mm hole and back out to the ambient air. At the same time, the pump in the leak diagnostic unit is monitored and the reference values stored for later use to determine whether the tank system is leaking or not.

If a reference value for the pump is outside its unexpectedly high or low, or deviates too much, diagnostics is cancelled and a DTC is stored.

Function test

After the reference phase, the valve in the leak diagnostic unit is activated and controls the air flow to the fuel tank to pressurize the fuel tank system. This change of air flow will cause the load the pump to fall briefly before the pressure builds up in the fuel tank system. If the load does not change within permitted parameters within a permitted time, diagnostics is cancelled and a DTC is stored.

Checking the tank system, major leak (leak greater than 1.0 mm)

Diagnostics are carried out every time conditions for diagnostics are met.

The leak diagnostic unit pressurizes the fuel tank system and checks for leaks by monitoring the pressure the fuel tank system. The pressure is a calculated pressure, calculated using the measured pump power consumption. If the pressure stabilizes and/or does not exceed 1500 Pa within 450 seconds, this is interpreted as a leak from the fuel tank system. Diagnostics are cancelled and a DTC for major leak is stored.

Checking the fuel tank system, minor leak (leakage greater than 0.5 mm but less than 1.0 mm)

The diagnostic for minor leaks is run every other time that the conditions for the diagnostic are met. Otherwise diagnostics stop after checking for major leaks.

The leak diagnostic unit continues to pressurize the fuel tank system. The Engine control module (ECM) checks for leakage in the fuel tank system by measuring the relationship between reached pressure and flow from the leak diagnostic pump during pressurization. In a sealed system the relationship between these must be linear. Any deviations from the linear relationship are calculated and used to determine how well sealed the tank system is.

A diagnostic trouble code (DTC) is stored if a minor leak is detected within 15 minutes.

Scheme 105

All gases that evaporate from fuel in the fuel tank must be led to and stored in the evaporative emission system (EVAP) canister so that they can be directed into the engine for combustion. In order to detect leakages that cause gas to evaporate into the air, the fuel tank system is diagnosed for leakage. The fuel tank system consists of fuel tank, , fuel filler pipe (7), EVAP canister (2), EVAP valve (1), air cleaner (4), leak diagnostic unit (3) and all cables between these components. The fuel tank system has a leak diagnostic unit that makes it possible to diagnose any leaks. The unit pressurizes the fuel tank system when the ignition is switched off if the conditions for leak diagnostics are met. The control module can detect faults in the function of the diagnostic unit and leakage that is 0.5 mm (minor leak) or greater (major leak, fuel filler cap missing).

The leak diagnostic unit consists of a pump and a valve that controls the air flow in the unit. The fuel tank system tests for leaks by measuring the power consumption of the pump. The power consumption of the pump corresponds to a certain pressure in the fuel tank system. During diagnosis, the rate at which the pressure can build up is checked, taking into account the quantity of fuel in the tank. The quicker the pressurization the better the fuel tank system is sealed.

Conditions for diagnosis

The diagnosis begins when all the following conditions are met

1. There must be no diagnostic trouble code (DTC) stored for the following components or functions: the power stage for the pump in the leak diagnostic unit the power stage for the valve in the leak diagnostic unit the power stage for the EVAP canister purge valve the EVAP canister purge valve.
2. Engine off for at least 5 hours (context), engine running for at least 20 minutes (context)
3. Ignition off
4. Vehicle speed 0 km/h
5. Engine coolant temperature (ECT) +4°C or higher
6. Maximum altitude of 2500 meters above sea level
7. Outside temperature between +4 and +35°C
8. Stable signal from the fuel level sensor
9. Fuel volume in the tank between 15-85%
10. Battery voltage between 11.0-14.5 V. The voltage must be stable
11. EVAP canister purge valve closed
12. Low volume in the canister.

Diagnostic phases

The diagnostic is divided into the following phases and is carried out in sequence when all conditions for the diagnostic have been met.

1. Reference phase 1
2. Function test
3. Leak diagnostic.

Reference phase and function test

(the illustration is a diagram of a fault free fuel tank system) Before the actual leak diagnostic begins, the control module enters a reference phase for leakage and checks the components in the system.

Reference phase 1 and reference phase 2

During the reference phases (1-2) for leakage that is 0.5 mm, the pump in the leak diagnostic unit pumps ambient air through a 0.5 mm hole and back out to the ambient air. At the same time, the power consumption of the pump is measured and stored in the control module (A). The stored value for the power consumption of the pump corresponds to a leakage of 0.5 mm.

Function test

If the value for the power consumption of the pump is too high or low during reference phase1 (1-2), or if the value varies too much during reference phase 1 (1-2), the diagnostic is cancelled and starts again the next time the conditions for the diagnostic are met. Diagnostic trouble code (DTC) ECM-431D, faulty signal, is stored if the diagnostic is cancelled 10 times due to excessive variation in the power consumption of the pump.

After the reference phase, the valve (2) in the leak diagnostic unit is activated and controls the air flow to the fuel tank to pressurize the fuel tank system. This change of air flow will cause the power consumption of the pump to fall briefly before the pressure builds up in the fuel tank system (3). Diagnostic trouble code (DTC) ECM-431D, signal missing, is stored if the value for the power consumption of the pump drops too quickly, too slowly or not at all.

Leak diagnostic

(the illustration is a diagram of a fault free fuel tank system). As long as diagnostic trouble code (DTC) ECM-431D is not stored, the leak diagnostic will be carried out after the reference phase and the function test.

Major leak

(leaks >1.0 mm) The diagnostic for "major leaks" is carried out every other time when the diagnostic conditions are met. The leak diagnostic unit pressurizes the fuel tank system, measures the power consumption of the pump (4) and compares this with a calculated desired value (B). If the measured value does not reach the calculated desired value within a certain amount of time (this time is determined by the fuel level in the tank), the function of the leak diagnostic unit is rechecked by running reference phase 2 again to check that low power consumption has not led to changes in the components. Diagnostic trouble code ECM-400C, major leak, is generated if the power consumption of the pump is OK during reference phase 2.

Diagnostic trouble code (DTC) ECM-4338 (fuel tank filler cap missing) will also be stored and the driver will receive a text message in the Driver Information Module (DIM) when a major leak is detected by the Engine Control Module (ECM).

Minor leak

Scheme 106

(leaks > 0.5 mm < 1.0 mm). The diagnostic for "minor leaks" is carried out every 14th time when the diagnostic conditions are met. The diagnostic for major leaks is always run before the diagnostic for minor leaks. The leak diagnostic unit continues to pressurize the fuel tank system (5). If the measured value (6) is the same or less than the value stored in the reference phase (A) after a certain amount of time (determined by the fuel level in the tank), reference phase 2 (7) is run to ensure that the lower power consumption (6) is not the result of changes in components. If the measured power consumption during the second reference phase (7) is lower than that measured during pressurization (6), the control module interprets this as meaning that the fuel tank system is sealed. Diagnostic trouble code ECM-400C, minor leak, is generated if the measured power consumption from the second reference phase (7) is the same or higher than that measured during pressurization (6).

Camshaft diagnostics

The task of the variable camshaft is to alter the camshaft position to minimize emissions and optimize the engine performance. The camshaft displacement in relation to the crankshaft is calculated using the engine load and engine speed (RPM).

The exhaust camshaft is variable, the intake camshaft has a set position in relation to the crankshaft.

The diagnostic consists of 4 components

1. When the when the ignition is switched on an electrical check is carried out on the signal cable, the power supply cable and the solenoid. The check is carried out for a short-circuit to supply voltage/ground and open-circuit. With the engine running this diagnostic is switched off.
2. The camshaft position is checked in comparison to the flywheel, when the camshaft is in its 0-position (mechanical resting position). If the deviation is excessive the variable camshaft is switched off.
3. In case of larger controlled deviations at the variable camshaft the time taken to regulate to the control value is measured. This time is used partially to determine how long it takes to alter the camshaft angle and partially to switch off the variable camshaft if the time exceeds a certain maximum time. The information about the speed of the camshaft angle change is used in the control strategy. The camshaft uses the engine oil and oil pressure to turn. The turning time depends on oil pressure, viscosity etc. which in turn depends on oil temperature and quality etc.
4. The camshaft position (CMP) sensor is compared with the flywheel sensor to check if the camshaft position (CMP) sensor detects all lobes.

Mechanical 0 position

For turbocharged engines the camshaft mechanical 0-position is in the performance position.

Scheme 107

The three-way catalytic converter (TWC) stores oxygen found in the exhaust gases and uses it to make toxic gases more environmentally friendly. The catalytic converter is a three-way catalytic converter (TWC) in which HC (hydrocarbons) and CO (carbon monoxide) are oxidized and NO x (nitrogen oxides) are reduced. As the three-way catalytic converter (TWC) ages its ability to store oxygen drops. This reduces the conversion capacity of the three-way catalytic converter (TWC). To avoid dangerous emissions the engine control module (ECM) checks three-way catalytic converter (TWC) efficiency. This check is carried out as follows.

Two heated oxygen sensors (HO2S) are used to check the three-way catalytic converter (TWC) one upstream and one downstream of the catalytic converter. The main function of the heated oxygen sensors (HO2S) is to measure the oxygen content in the exhaust gases so that the engine control module (ECM) can maintain the fuel/air mixture at around lambda=1. This mixture provides optimum three-way catalytic converter (TWC) efficiency. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared (amplitude is a measure of signal oscillation).

When three-way catalytic converter (TWC) efficiency is good and the fuel/air mixture is normal, the front heated oxygen sensor (HO2S) signal switches between rich and lean while the rear heated oxygen sensor (HO2S) signal is even. When three-way catalytic converter (TWC) efficiency is poor and the fuel/air mixture is normal, the rear heated oxygen sensor (HO2S) signal switches between rich and lean because the exhaust gases are passing straight through the three-way catalytic converter (TWC) without being converted.

If rear sensor amplitude becomes too great in relation to the front sensor signal for a number of diagnostic checks, diagnostic trouble code (DTC) ECM-4801 Catalytic converter efficiency will be stored.

If the fuel/air mixture does not ignite in the ignition stroke the engine is misfiring. The engine control module (ECM) detects misfires by registering the time between two segments of the flywheel.

The time between the two segments varies depending on

1. misfiring
2. driveline oscillations
3. normal variations caused by uneven combustion
4. flywheel mechanical tolerances.

The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. An adaptation of the flywheel signal is being made in order to eliminate the mechanical fault in the flywheel. Two camshaft revolutions are divided into five intervals for 5 cylinder engines and six intervals for 6 cylinder engines. The aim of this modification is to filter out the normal distortion present in the flywheel. By registering the time difference between the intervals and comparing this with the normal distortion in the flywheel, misfires can be gauged. In order for the engine control module (ECM) to register misfires, the flywheel must be adapted. Misfire diagnostics are shut off until the flywheel is adapted for the first time. This value is saved and then used in subsequent operating cycles.

Adaptation of the flywheel is done when

1. the engine speed (RPM) is between 2300 rpm and 3000 rpm
2. the load should exceed 40% of relative load (RL), which corresponds to normal forward travel on a smooth road at approximately 100 km/h.

Flywheel adaptation takes approximately 60 seconds.

Drive line oscillations, caused by uneven road surfaces for example, may lead to uneven engine operation. Drive line oscillations will be registered by the ABS system and the information sent to the engine control module (ECM). The engine control module (ECM) uses this information to differentiate between these oscillations and real misfiring. Misfire diagnostics are shut off in the event of drive line oscillations

Misfire diagnostics are also shut off when

1. leak diagnostic, when leak diagnostics are taking place
2. diagnostic trouble codes (DTCs) in the flywheel sensor, mass air flow (MAF) sensor, engine coolant temperature (ECT) sensor and leak diagnostic.

Misfiring lights the malfunction indicator lamp (MIL). In the event of misfiring, if there is risk of damage to the three way catalytic converter, the malfunction indicator lamp (MIL) will flash and then switch to a constant light.

The engine control module (ECM) registers and stores the rpm and load ranges within which the misfire occurred. For the diagnostic trouble code (DTC) to be stored, the misfire must occur a further two times within the same rpm and load ranges. The malfunction indicator lamp (MIL) lights if the diagnostic trouble code (DTC) for misfire is stored in the previous operating cycle and a new diagnostic trouble code (DTC) for misfire is received in the next operating cycle.

If the misfire stops, the requirements for the rpm and load ranges must be met without any misfires before the engine control module (ECM) will begin counting down to extinguish the warning lamp and erase stored diagnostic trouble codes (DTCs) for misfiring.

Four different conditions for diagnostics

Trip

When all diagnostic functions have been gone through.

Drive cycle

Begins 15 seconds after the engine starts and finishes when the engine is switched off.

Warm-up cycle

Begins when the engine starts and engine coolant temperature (ECT) is below 40°C (104°F) and finishes when the engine temperature is above 84°C (183.2°F).

Time

Some diagnostics are carried out a set amount of time after a particular occurrence (for example when vehicle speed is above 23 km/h (14.3 mph)).

Emissions related diagnostic functions

The engine control module (ECM) checks that the emissions related functions are working. These systems are checked by an ongoing diagnostic function. The diagnostic function checks that the relevant components and the actual function in the system are working. It is called a trip when all diagnostic functions have been gone through. Trip time may vary depending on driving style, but normally it takes approximately 25 minutes fir mixed driving.

Diagnostic trouble code (DTC) memory

When the engine control module (ECM) detects a fault, the diagnostic trouble code (DTC) is stored with the qualifier and status in the unit DTC memory. For certain types of diagnostic trouble codes (DTCs) the missing signal is replaced with a substitute value so that the system can continue to operate.

If the fault disappears, the diagnostic trouble code (DTC) will be present for a longer time in the diagnostic trouble code (DTC) memory although the status of the code will have changed.

For more information about the electronic throttle unit system and related components such as the throttle unit, accelerator pedal sensor, stop lamp switch, clutch pedal sensor switch and brake pedal position sensor, see Design and Function .

Camshaft diagnostics (CVVT)

In addition to the electrical check of the camshaft reset valve, the engine control module (ECM) checks that the camshaft position is correct and that the control (deployment and return phases of the cam timing) functions satisfactorily. The control module uses the signals from the camshaft position (CMP) sensor (camshaft position) and engine speed (RPM) sensor (crankshaft position) in the diagnosis.

Checking the camshaft position

The control module checks that the camshaft 0-position (mechanical rest position) is correct. At idle speed camshaft control is not activate. The control module checks the camshaft deviation from the 0 position, that is how much the camshaft flanks deviate from the predetermined positions on the crankshaft.

The camshaft position is stored in the control module as an adaptation value. The diagnostic trouble code (DTC) is stored in the engine control module (ECM) if the adaptation value is too high or too low. The adaptation value for the camshaft with camshaft control can be read off using VIDA.

Checking camshaft control

Active camshaft control checks that the camshaft assumes the position the control module intends the camshaft to move to, that is that the correct camshaft angle is obtained. This is done by measuring the time it takes for the system to reach the desired position (the time for the actual change position to reach the desired change position). A diagnostic trouble code (DTC) is stored in the Engine Control Module (ECM) if the cam timing does not reach the desired value within a specified time. The function can be tested using VIDA, quick test camshaft control.

The front heated oxygen sensor (HO2S) is a lineal type and functions with current control. Therefore it is not possible to measure the signals from the heated oxygen sensor (HO2S) using a multimeter. The rear heated oxygen sensor (HO2S) is a binary type as with earlier heated oxygen sensors (HO2S).

The Engine Control Module (ECM) checks the heated oxygen sensors (HO2S) when the conditions for diagnostics have been fulfilled.

The following faults can be registered by the control module

1. Electrical fault in the circuits for the heated oxygen sensors (HO2S) and for the heated oxygen sensor (HO2S) preheating
2. Adaptation. The control module checks that the long-term fuel trim is not higher or lower than the pre-defined values
3. Large difference between the front and rear heated oxygen sensor (HO2S) adaptation. The control module checks that the difference between the rear and front heated oxygen sensor (HO2S) adaptation is not too great. The fault may be in the front or rear heated oxygen sensor (HO2S) or the wiring
4. Heated oxygen sensor (HO2S) dynamics. The control module checks that the changeover period between rich and lean mixtures is not too long
5. Unlikely signals between the front and rear heated oxygen sensors (HO2S). When the control module registers a rich mixture in the front probe at the same time that a lean mixture is registered in the rear probe or vice versa.

For further information about heated oxygen sensor (HO2S) diagnostics, see "Diagnostic trouble code (DTC) information" for diagnostic trouble codes (DTCs) in VIDA, information manager.

Misfire diagnostics

If the fuel/air mixture does not ignite completely in the ignition stroke the engine is misfiring. The engine control module (ECM) detects the misfire by registering deviations in the rotation of the flywheel.

Deviation in flywheel rotation is due to

1. Driveline oscillations Incorrect fuel/air mixture Poor ignition spark Insufficient compression.
2. Normal variations caused by uneven combustion Incorrect fuel/air mixture Poor ignition spark Insufficient compression.
3. Flywheel mechanical tolerances Incorrect fuel/air mixture Poor ignition spark Insufficient compression.
4. Misfire, caused by Incorrect fuel/air mixture Poor ignition spark Insufficient compression.

Diagnostics

The mechanical tolerances and oscillations in the drive line disrupt the signal. This makes it difficult to determine if a misfire has occurred or if the detection is incorrect.

The signal from the flywheel is adapted to filter out the irregular rotation. This eliminates the mechanical variations in the flywheel.

Two camshaft revolutions are divided into five intervals for 5 cylinder engines and six intervals for 6 cylinder engines.

Misfires can be detected by registering the time difference between the intervals and comparing this with the filtered time difference in the flywheel. If the flywheel signal has not been adapted, the diagnostic is active. However this cannot identify misfires as accurately as an adapted flywheel signal. The adaptation is carried out at different loads and engine speed ranges. For the values to be set in the different ranges, the deviation in rotation must be within certain fixed limits.

Drive line oscillation, caused by uneven road surfaces for example, may lead to uneven engine operation. Drive line oscillations are registered by the accelerator in the brake control module (BCM) which sends this information to the engine control module (ECM).

The misfire diagnostic is shut off when

1. The brake control module (BCM) transmits information to the engine control module (ECM) about driveline oscillations
2. A fault has been detected by the engine control module (ECM) in the engine speed (RPM) sensor, mass air flow (MAF) sensor or engine coolant temperature (ECT) sensor
3. When one of the DSTC (Dynamic stability and traction control), traction control or Anti-lock Brake Systems (ABS) are active.

The following applies from model year 2005

The injector for that cylinder will be disabled if the engine control module (ECM) detects misfiring in a cylinder. This will cut the fuel supply to the cylinder.

Diagnostic trouble code (DTC) management

The engine control module (ECM) determines how much the engine is misfiring by counting the number of misfires during a certain number of engine revolutions. If the engine control module (ECM) detects a particular number of misfires below 1000 rpm it is interpreted as emission related misfires. If the misfires exceed a certain value during 200 engine revolutions, this is interpreted as misfiring which damages the three-way catalytic converter (TWC).

Diagnostic trouble codes (DTC) for misfiring will light the malfunction indicator lamp (MIL). If there is risk of damage to the three way catalytic converter, the malfunction indicator lamp (MIL) will flash during misfiring and then switch to a constant light.

The engine control module (ECM) registers and stores the rpm and load ranges within which the misfire occurred. For the diagnostic trouble code (DTC) to be stored, the misfire must occur a further two times within the same rpm and load ranges.

In the event of emissions related misfiring, the malfunction indicator lamp (MIL) lights during the second operating cycle and a diagnostic trouble code (DTC) is stored.

If the misfire stops, the requirements for the rpm and load ranges must be met without misfiring before the engine control module (ECM) will begin counting down to extinguish the warning lamp and erase the stored diagnostic trouble codes (DTCs) for misfiring.

Three-way catalytic converter (TWC) diagnostics

The three-way catalytic converter (TWC) stores oxygen found in the exhaust gases and uses it to make toxic gases more environmentally friendly. The catalytic converter is a 3-way catalytic converter in which HC (hydrocarbons) and CO (carbon monoxide) are oxidized and NO x (nitrous oxide) is reduced. As the three-way catalytic converter (TWC) ages, its ability to store oxygen is reduced. The conversion capacity of the three-way catalytic converter (TWC) is reduced and unburned residue which is harmful to environment is released. To reduce the environmentally damaging emissions, the engine control module (ECM) checks the efficiency of the three-way catalytic converter (TWC). In brief, this check is carried out as follows.

Two heated oxygen sensors (HO2S) are used to check the three-way catalytic converter (TWC) one upstream and one downstream of the catalytic converter. The main function of the heated oxygen sensors (HO2S) is to measure the oxygen content in the exhaust gases so that the engine control module (ECM) can maintain the fuel-/air mixture at around lambda=1. This mixture provides optimum three-way catalytic converter (TWC) efficiency. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared (amplitude is a measure of signal oscillation).

When three-way catalytic converter (TWC) efficiency is good and the fuel-/ air mixture is normal, the front heated oxygen sensor (HO2S) signal switches between rich and lean while the rear heated oxygen sensor (HO2S) signal is even. When three-way catalytic converter (TWC) efficiency is poor and the fuel-/ air mixture is normal, the rear heated oxygen sensor (HO2S) signal switches between rich and lean because the exhaust gases are passing straight through the three-way catalytic converter (TWC) without being converted.

If the amplitude of the rear sensor becomes too great in relation to the amplitude of the front sensor for a number of checks, a diagnostic trouble code (DTC) will be stored for catalytic converter efficiency.

Camshaft diagnostics

Catalytic converter diagnostic

Misfire diagnostic

Throttle diagnostic

Camshaft diagnostics

Catalytic converter diagnostic

Misfire diagnostic

Throttle diagnostic

Scheme 108

If the fuel/air mixture does not ignite in the ignition stroke it can be said that the engine is misfiring. The flywheel is divided into 5 sectors where every sector corresponds to a special cylinder. The engine control module (ECM) detects misfires by registering the time between two sectors of the flywheel.

The time between the two segments varies depending on

1. misfiring
2. driveline oscillations
3. normal variations caused by uneven combustion
4. flywheel mechanical tolerances

1. The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. To eliminate mechanical faults/damage to the flywheel the flywheel signal is adapted. Two crankshaft rotations are split into 5 intervals for 5 cylinder engines. The purpose of adaptation is to filter out the tolerances in the flywheel and resonance in the engine. By registering the time deviations between the sectors on the flywheel misfiring can be detected. In order for the engine control module (ECM) to be able to register misfires, the flywheel must be adapted. Misfire diagnostics are shut off until the flywheel is adapted for the first time. This adaptation value is saved and then used in subsequent operating cycles.

Adaptation of the flywheel is done when

1. engine speed is between 2300 rpm and 3000 rpm
2. the load exceeds 40 % of relative load

Flywheel adaptation takes approximately 60 seconds.

1. Drive line oscillations, caused by uneven road surfaces for example, may lead to uneven engine operation (false misfiring). This is registered by the ABS module which sends this information to the engine control module (ECM) which uses this information in order to separate the oscillations from genuine misfiring. The misfire diagnostic is shut off when oscillations occur in the drive line caused by uneven road surfaces.

Misfire diagnostics are also shut off when

1. leak diagnostic, when leak diagnostics are taking place
2. diagnostic trouble codes (DTCs) in the engine speed (RPM)/position sensor, mass air flow (MAF) sensor, engine temperature sensor and the leak diagnostic and ABS.

1. Misfiring lights the malfunction indicator lamp (MIL). In the event of misfiring, if there is risk of damage to the three way catalytic converter, the malfunction indicator lamp (MIL) will flash and then switch to a constant light.
2. The engine control module (ECM) registers and stores which engine speeds and load ranges the misfiring occurred. Misfiring must occur within the same engine speed and load range again for a diagnostic trouble code (DTC) to be set. The malfunction indicator lamp (MIL) is lit if the diagnostic trouble code (DTC) for misfire is stored in the previous operating cycle and a new diagnostic trouble code (DTC) for misfire is received in the next operating cycle.
3. If the misfire stops, the requirements for the rpm and load parameters must be met before the engine control module (ECM) will begin counting down to extinguish the warning lamp and erase stored diagnostic trouble codes (DTCs) for misfiring.

Scheme 109

New sensors and functions which are different to previously known principles are marked with bold text .

Scheme 110

Sensors and functions which are different to previous types are marked in bold text .

Vapor which evaporates from the fuel in the fuel tank is routed to and stored in the EVAP canister from where it is introduced into the combustion process via the canister purge (CP) valve and negative pressure in the intake manifold.

A leak diagnostic has been introduced in certain markets to ensure that there are no leaks in the fuel tank system.

The diagnostic is designed to detect leakage corresponding to a 1mm or larger hole.

The fuel tank system consists of fuel tank, fuel filler pipe, EVAP canister, canister purge (CP) valve and all pipes between these components. To be able to diagnose the fuel tank system, it is also equipped with fuel tank pressure sensor and EVAP canister shut-off valve.

The diagnostic is divided into different phases in which the various components are tested. If a fault is detected in any of the phases the diagnostic is interrupted and the diagnostic trouble code (DTC) for the component identified is stored. Diagnosis is carried out in the following stages

1. The fuel tank pressure sensor is checked for an unstable signal. Diagnostic trouble code (DTC) for a faulty fuel tank pressure sensor is stored if the signal deviates more than +/- 1 kPa more than 5 times in 5 seconds. The fuel tank pressure is checked so that it is stable and that the short-term fuel trim is not too low.
2. The EVAP canister shut-off valve closed and an evaporation check is carried out. By gauging how much fuel tank pressure increases value for how much fuel evaporates is provided, and this value is used later to calculate leakage flow. If fuel tank pressure sinks, this indicates that the canister purge (CP) valve is leaking and diagnostic trouble code (DTC) for an open canister purge (CP) valve is stored.
3. The EVAP canister shut-off valve opens, the tank system is open. The canister purge (CP) valve is pulsed and because of the negative pressure in the intake manifold the engine starts to suck air through the EVAP canister. Because EVAP canister shut-off valve is open, the fuel tank pressure sinks slowly. If fuel tank pressure sinks rapidly this indicates that the EVAP canister shut-off valve is clogged and the diagnostic trouble code (DTC) for EVAP canister shut-off valve shut is stored.
4. EVAP canister shut-off valve closes and the canister purge (CP) valve pulses with a duty cycle of approximately 17%. The pressure in the tank then falls to -1 kPa. If this pressure is not reached within 10 seconds it indicates a larger leak in the fuel tank. and the diagnostic trouble code (DTC) for a large leak is stored. If the fuel tank pressure does not change within 2 seconds it indicates a defective fuel tank pressure sensor or clogged piping. The diagnostic trouble code (DTC) for a large leak is stored.
5. The canister purge (CP) valve is closed and the EVAP canister shut-off valve is still closed and there is negative pressure in the fuel tank. This negative pressure will decrease slowly. The decrease rate depends on fuel level, fuel evaporation and any leaks. Leakage flow is calculated by comparing pressure increase speed with the pressure decrease speed from stage 4 and by compensating for the evaporation measured in stage 2. If the calculated leakage flow exceeds a certain level this indicates a smaller leakage in the fuel tank system and diagnostic trouble code for small leak is stored.
6. The EVAP canister shut-off valve opens, the EVAP function is enabled and the diagnostic test is finished.

During the different phases when the system gauges whether the fuel tank system pressure acts normally or not, there are a number of circumstances which are taken account of, for example

1. the amount of fuel in the tank
2. height above sea level
3. fuel temperature and evaporation

The system can calculate this information. Therefore it is not possible to describe how quickly or how much the pressure is permitted to increase or fall in the different phases.

To carry out the diagnostic it is necessary that

1. there are no diagnostic trouble codes (DTCs) registered for: Vehicle speed signal, canister purge (CP) valve, EVAP canister shut-off valve and fuel tank pressure sensor
2. fuel trim must be active
3. engine idling
4. Speed is 0 km/h (0 mph)
5. the car is below 2500 meters above sea level
6. outside temperature is above -8°C (17.6°F)
7. engine coolant temperature (ECT) must be above -8°C (17.6°F) and below 120°C (248°F)
8. the pressure in the tank is above -1 kPa
9. the concentration of fuel fumes in the EVAP canister must not be too high

The diagnostic test starts at the earliest 17 minutes after the engine has started when all conditions have been fulfilled, and takes approximately 30 seconds.

If the diagnostic is interrupted for any reason, the engine control module (ECM) will try to start again the next time all conditions are met. The engine control module (ECM) performs a maximum of 4 diagnostic attempts during an operating cycle. If no faults are detected the diagnostic is not active again until the engine is switched off and on again. If a fault is detected two further attempts are made to evaluate the fault.

Scheme 111

ME 7.0 (Motronic, Electronic-gas 7.0) is a further development of Motronic 4.4 and has many similarities to DENSO EMS regarding components and their functions.

ME 7.0 on all B52X4T engines from model year 1999.

The biggest new feature regards the communication between the ECM and other modules, which occurs via network.

The system has other new features

1. ETS (Electronic Throttle System) that includes ETM (Electronic Throttle Module) and APM (Accelerator Pedal Module)
2. CVVT (Continuously Variable Valve Timing)

The following modules communicate by ECM via the network

1. TCM (Transmission Control Module)
2. ETM (Electronic Throttle Module)
3. ABS (Antilock Braking System)
4. CDM (Can and Driver information Module)
5. DLC (Diagnostic Link Connector)

ME 7.0 contains sensors that operate according to the previously known principles and sends its information by analog signals to the ECM.

As applies to controlled components these also function to known principles, with a few exceptions. These exceptions are covered on the following pages.

For more information about the electronic throttle unit system and related components such as the throttle unit, accelerator pedal sensor, stop lamp switch, clutch pedal sensor switch and brake pedal position sensor, see Design and Function .

Scheme 112

Turbocharger (TC) boost pressure is controlled by the boost pressure control (BPC) valve whose pressure regulator is affected by the pressure from the turbocharger (TC).

The engine control module (ECM) determines current throttle angle and boost pressure to achieve the calculated torque.

The Engine Control Module (ECM) affects the controlling pressure using the turbocharger (TC) control valve.

When the pressure increases the boost pressure control (BPC) valve pressure regulator is affected. When boost pressure has increased to the maximum permissible value the boost pressure control (BPC) valve opens and part of the exhaust gases bypass the turbocharger (TC) turbine which limits the boost pressure. Turbocharger (TC) control takes place constantly by measuring the current boost pressure and comparing it to the requested boost pressure.

Diagnostics, fault-tracing

Diagnostics, fault-tracing

Diagnostics, fault-tracing