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
- front heated oxygen sensor (HO2S) mean signal voltage
- rear heated oxygen sensor (HO2S) control
- 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
- the front heated oxygen sensor (HO2S) has started control
- the rear heated oxygen sensor (HO2S) has reached operating temperature
- catalytic converter temperature exceeds 112°C (calculated by the engine control module (ECM))
- engine speed (RPM) is between 1500-2300 RPM
- 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
- The EVAP system (diagnostic trouble code (DTC) EFI-315)
- three-way catalytic converter (TWC) (diagnostic trouble code (DTC) EFI-443)
- heated oxygen sensor (HO2S) preheating (diagnostic trouble code (DTC) EFI-521 or EFI-522)
- 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 1066
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
- boost pressure at high altitude
- injection time when starting at high altitude.
At heights above 2400 meters the following are disabled
- leak diagnostic
- pulsed secondary air injection (PAIR) diagnostic
- 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 0 V and 5 V.
The sensor is supplied with a stabilized voltage of 5 V 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 1067
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
- housing
- sleeve
- piezo-electric crystal
- contact strips
- damping weight
- washer
- 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 1068
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
- leak diagnostic
- pulsed secondary air injection (PAIR) system diagnostic
- misfire diagnostic
- boost pressure control diagnostic.
- 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 5 V. 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 1069
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
- 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
- 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.
- 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 1070
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.
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
- 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.
- 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.
- 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.
- 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 1071
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.
Misfire Diagnostic
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
- misfiring
- driveline oscillations
- normal variations caused by uneven combustion
- 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
- the engine speed (RPM) is between 2300 RPM and 3000 RPM
- 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
- leak diagnostic, when leak diagnostics are taking place
- 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)).
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.
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 .
See Camshaft diagnostics
Catalytic converter diagnostic
See Catalytic converter diagnostic
See Misfire diagnostic
See Throttle diagnostic
See Camshaft diagnostics
See Catalytic converter diagnostic
See Misfire diagnostic
See Throttle diagnostic
Scheme 1072
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
- misfiring
- driveline oscillations
- normal variations caused by uneven combustion
- 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. 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
- engine speed is between 2300 RPM and 3000 RPM
- the load exceeds 40% of relative load
Flywheel adaptation takes approximately 60 seconds.
- 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
- leak diagnostic, when leak diagnostics are taking place
- 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.
- 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 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.
- 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 1073
New sensors and functions which are different to previously known principles are marked with bold text .
| Number | Component | Signal type/function |
|---|---|---|
| 2/11 | Relay, engine cooling fan (FC) | Engine cooling fan (FC) speed, high speed or low speed. |
| 2/22 | Air conditioning (A/C) relay | Connecting and disconnecting air conditioning (A/C) compressor. |
| 2/23 | Fuel pump relay | Activation and deactivation of fuel pump. |
| 2/32 | System relay | Controlled by the engine control module (ECM) provides engine sensors and functions with voltage supply. |
| 4/30 4/6 | ECC MCC | Signals engine coolant temperature to climate control system which can then determine how the blower fan should be controlled after cold start. |
| 4/28 | TCM Transmission Control Module | For signals transmitted between the engine control module (ECM) and the Transmission Control Module (TCM) refer to CAN Communication . |
| 4/50 | ETM Electronic Throttle Module | For signals transmitted between the engine control module (ECM) and the electronic throttle module refer to CAN Communication . |
| 5/1 | CDM Can and Driver information Module | For signals transmitted between the engine control module (ECM) and the CAN and Driver information Module refer to CAN Communication . |
| 7/15 | Front heated oxygen sensor (HO2S) | Power supply for heating PTC element. |
| 7/82 | Rear heated oxygen sensor (HO2S) | Power supply for heating PTC element. |
| 8/6-10 | Injectors | Controlled individually (sequentially). |
| 8/18 | Canister purge (CP) valve | Continuously controlled, it controls the flow from EVAP canister to engine intake side. |
| 8/19 | Continuously Variable Valve Timing control valve (CVVT) | The Continuously Variable Valve Timing valve is continuously controlled by the engine control module (ECM) and controls the oil pressure to the variable camshaft on the exhaust side. |
| 8/28 | Turbocharger (TC) control valve | Controls turbocharger (TC) boost pressure |
| 8/44 | Fresh air valve, Canister purge (CP) | The valve is either off or on and opens or closes the canister fresh air intake during a leak diagnostic. |
| 20/3-7 | Ignition coil/power stage for cylinders 1-5 | Separate ignition coil with integrated power stages for each cylinder. Gives shorter charging interval and more power. |
| Malfunction indicator lamp (MIL) USA/CDN = Check Engine Other = engine symbol | The lamp lights up for faults affecting the emissions. The lamp flashes for misfires which cause risk of damage to the catalytic converter. Can also light up when requested by the Transmission Control Module (TCM) and the electronic throttle module. | |
| ETS warning lamp | Can be activated by either the engine control module (ECM) or the electronic throttle module depending on where the fault was found in the system. | |
| Cruise indicator lamp | Activated by the engine control module (ECM) and informs the driver that the cruise control is active. |
Scheme 1074
Sensors and functions which are different to previous types are marked in bold text .
| Number | Component | Information type/explanation |
|---|---|---|
| 3/1 | Ignition switch + 50 supply | Provides early information to the Engine Control Module (ECM) to prepare for start. |
| 3/4 | Cruise control lever | Gives information about selected speed to engine control module (ECM) via the electronic throttle module to control the throttle. The cruise control software in integrated into the engine control module (ECM). |
| 3/9 | Stop (brake) lamp switch | Informs engine control module (ECM) that the car is braking. The signal is a safety feature in addition to the brake pedal sensor. The engine control module (ECM) carries out a range test between the signals from both sources. |
| 4/30 4/6 | ECC MCC | Provides information if the air conditioning (A/C) is switched on or not. The engine control module (ECM) controls connection/disconnection of the compressor dependent on load, engine speed (RPM), engine coolant temperature, air conditioning (A/C) pressure. |
| 7/6 | Oil pressure switch | Provides information about engine oil pressure. The information is sent on to the Can and Driver information Module which lights the warning lamp. |
| 7/8 | Air conditioning (A/C) pressure sensor (linear) | Provides information using a linear signal about any pressure changes on the high-pressure side. Depending on the pressure the engine control module (ECM) can activate the engine cooling fan (FC) at high/low speed and shut off the air conditioning (A/C) compressor. The engine control module (ECM) can also provide information about low volume in the air conditioning (A/C) system. |
| 7/15 | Front heated oxygen sensor (HO2S) (linear signal) | New signal characteristics. Provides information about the oxygen level in the exhaust gases upstream of the catalytic converter. |
| 7/16 | Engine coolant temperature sensor | Provides information about engine coolant temperature (ECT). Located in the thermostat housing on the front edge of the engine. |
| 7/17 | Mass air flow (MAF) sensor (heated film principle) | Provides information about the intake air mass. Has no resistor for the intake air temperature is complemented instead by a separate sensor 7/77 downstream of the charge air cooler (CAC). |
| 7/21 | Camshaft position (CMP) sensor | New signal characteristics. Provides information about cylinder intake and compression phase. Gives shorter starting time, approximately 0.5 seconds. |
| 7/23 7/24 | Knock sensor (KS) 1 Knock sensor (KS) 2 | Provides information if the engine knocks. The engine control module (ECM) always knows each cylinders exact position from the new camshaft position (CMP) sensor. A turbocharged engine can be subjected to greater pressure variations in combustion chamber and must therefore have signals from 2 knock sensors (KS). |
| 7/25 | Engine speed (RPM)/position sensor | Provides information about the crankshaft position and engine speed (RPM). Has flywheel adaptation for mechanical faults/damage. Like M 4.4 |
| 7/51 | Accelerator pedal (AP) position sensor | Provides information about current throttle opening. The signal is sent via two separate cables at the same time, one analog signal and one digital signal. |
| 7/53 | Low pressure sensor AC | Provides information about pressure changes on the low pressure side. |
| 7/73 | Engine coolant level switch | Provides information about engine coolant level. The information is sent further to the Can and Driver information Module which lights the low engine coolant level warning lamp. |
| 7/77 | Manifold absolute pressure (MAP) sensor | Provides information about the intake air actual temperature after the charge air cooler (CAC). Used for boost pressure control. The sensor is used together with intake air pressure sensor 7/81. |
| 7/81 | Manifold absolute pressure (MAP) sensor | Provides information about the intake air actual pressure after charge air cooler (CAC). The most important sensor for boost pressure control. The sensor is used together with intake air temperature sensor 7/77. |
| 7/82 | Rear heated oxygen sensor (HO2S) | Provides information about the oxygen level downstream of the catalytic converter (TWC) front section. Compared to previous versions it operates faster and can also affect the fuel/air mix to a greater extent. |
| 7/84 | Fuel tank pressure sensor | Provides information about pressure changes in the fuel tank system. Used for leak diagnostic. |
| 7/95 | Ambient air pressure sensor (located in engine control module (ECM) | Provides information about ambient air pressure. Affects injected fuel quantity at cold start at high altitude and leak diagnostic. |
| 7/105 | Ambient air temperature sensor | Provides information about ambient air temperature. The signal is used to switch off the leak diagnostic in cold weather. |
| 7/123 | Clutch pedal position sensor | Provides information that the clutch pedal is depressed and that the throttle should close. Used in certain markets to connect the so called Interlock function via VGLA which inhibits the starter motor. Also disconnects the cruise control. |
| 7/124 | Brake pedal sensor (located in the brake servo) | Provides information that the brake pedal is depressed and that the throttle should be closed in case of serious faults in the Electronic throttle system in order to move to idling speed when the brake pedal is depressed. The signal is used to disconnect the cruise control. |
| CAN | CAN communication | Exchange of information between the Engine Control Module (ECM) and the following units: ABS, TCM, CAN and driver module, electronic throttle module and DLC. |
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
- 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.
- 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.
- 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.
- 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.
- 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.
- 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
- the amount of fuel in the tank
- height above sea level
- 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
- 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
- fuel trim must be active
- engine idling
- Speed is 0 km/h (0 mph)
- the car is below 2500 meters above sea level
- outside temperature is above -8°C (17.6°F)
- engine coolant temperature (ECT) must be above -8°C (17.6°F) and below 120°C (248°F)
- the pressure in the tank is above -1 kPa
- 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 1075
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
- ETS (Electronic Throttle System) that includes ETM (Electronic Throttle Module) and APM (Accelerator Pedal Module)
- CVVT (Continuously Variable Valve Timing)
The following modules communicate by ECM via the network
- TCM (Transmission Control Module)
- ETM (Electronic Throttle Module)
- ABS (Anti-lock Braking System)
- CDM (Can and Driver information Module)
- 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 information.
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 1076
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
See Diagnostics, fault-tracing
See Diagnostics, Fault-Tracing