Electrical System - Diagnostics and Tests: Diagnosis Volvo V70 II

Camshaft Diagnostics (CVVT) - Bosch ME7.01 Engine Management System (B5234T3; 2002-2004)

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 appropriate scan tool.

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 appropriate scan tool, quick test camshaft control.

Catalytic Converter Diagnostic - Bosch ME7.01 Engine Management System (B5234T3; 2002-2004)

1. For 5 cylinder engines, see «Catalytic converter diagnostics 5 cylinder»(ref-406873-S19020657332011070100000)
2. For 6 cylinder engines, see «Catalytic converter diagnostics 6 cylinder»(ref-406873-S40398422202011070100000) .

Scheme 1

The three-way catalytic converter (TWC) stores oxygen from 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 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 three-way catalytic converter (TWC), one upstream of the converter and one in the center of the converter (the rear heated oxygen sensor (HO2S)). 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 allows for optimum catalytic conversion. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared (amplitude is a measure of signal oscillation).

When efficiency of the catalytic converter is good and the fuel / air mixture is normal, the front probe signal switches between rich and lean while the rear probe signal is steady. If the three-way catalytic converter (TWC) efficiency is poor but the fuel / air mixture is normal, the rear probe signal will also switch between rich and lean. This is because the exhaust gases flow straight through the three-way catalytic converter (TWC) without being acted on. 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.

Scheme 2

The three-way catalytic converter (TWC) stores oxygen from 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 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.

Three heated oxygen sensors (HO2S) check the common catalytic converter. One heated oxygen sensor (HO2S) is in front of the three-way catalytic converter (TWC) for each bank of cylinders and a common rear heated oxygen sensor (HO2S) in the center of the three-way catalytic converter (TWC). 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 allows for optimum catalytic conversion. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared (amplitude is a measure of signal oscillation).

When efficiency of the catalytic converter is good and the fuel / air mixture is normal, the front probe signals for banks 1 and 2 switch between rich and lean while the rear probe signal is steady. If the three-way catalytic converter (TWC) efficiency is poor but the fuel / air mixture is normal, the rear probe signal will also switch between rich and lean. This is because the exhaust gases flow straight through the three-way catalytic converter (TWC) without being acted on. 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.

Fuel Pressure Regulation, Diagnostics

General

The fuel pump control module has no functions for diagnostics. Fuel pressure regulation components and functions are diagnosed by the engine control module (ECM).

The following components/functions are diagnosed by the engine control module (ECM). Diagnostic trouble codes (DTCs) can be stored for each component/function

1. Fuel pump control module , the power supply is checked. A diagnostic trouble code (DTC) will be stored and the fuel pump will not work if there is no power supply to the fuel pump control module
2. Fuel pressure sensor with temperature sensor , the pressure and temperature signals are checked to see if they are outside the normal operating range of the sensor. If a fault in the fuel pressure sensor is detected, the fuel pump (FP) will run at full power and the pressure is governed by the by-pass valve in the fuel tank
3. Fuel pressure , the engine control module (ECM) compares the requested pressure with the measured pressure (the signal from the fuel pressure sensor). If the measured pressure deviates excessively from the requested pressure, or if the pressure pulses, a diagnostic trouble code (DTC) will be stored for incorrect fuel pressure. The diagnostic is not active if a diagnostic trouble code (DTC) for the fuel pressure sensor is stored. A diagnostic trouble code (DTC) for fuel pressure will be stored if there is a fault in the fuel pump
4. Communication cable. The engine cannot be started if there is a fault in the communication cable between the engine control module (ECM) and the fuel pump control module. A diagnostic trouble code (DTC) will be stored for the fault.

For further information about diagnostic trouble codes (DTCs), see Information, diagnostic trouble codes (DTCs) in appropriate scan tool.

Components/functions which cannot be diagnosed

If there is a fault in the by-pass valve in the tank unit, the starting process of the engine will take longer if the valve is leaking fuel when the fuel pump is off. If the valve does note open when there are pressure peaks in the fuel system, engine operation will be negatively effected, especially after engine braking.

Heated Oxygen Sensor (HO2S) Diagnostic

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 predefined 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 appropriate scan tool, information manager.

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 - Denso Engine Management System (B5244S; 2001-2002)

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

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 30-160km/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 3

Leak Diagnostics, General Index

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 appropriate scan tool.

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-406873-S22876112792011070100000)
2. Original version for model year 2005-, see: «Leak diagnostics, original version (2005-)»(ref-406873-S00685616352011070100000)
3. Improved version for all model years, see: «Leak diagnostics, improved version (2002-)»(ref-406873-S31668056772011070100000)

Scheme 4

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 appropriate scan tool when some of these conditions are ignored.

Conditions for diagnosis

The diagnosis begins when all the following conditions are met.

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 5

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

Scheme 6

(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

Scheme 7

(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 8

(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).

Scheme 9

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)

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)

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.

Misfire Diagnostics, Bosch ME7.01 Engine Management System (B5234T3; 2002-2004)

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.

Oil Level Sensor, Diagnostics

General

The engine control module (ECM) can diagnose the oil level sensor. A diagnostic trouble code (DTC) will be stored if an internal fault is detected in the oil level sensor or if there is an open-circuit or a short-circuit to ground or voltage in its wiring connectors. A diagnostic trouble code (DTC) will also be stored if the oil level is too low or high or if the oil level drops rapidly over a certain time (leakage).

The pulse ratio of all the oil level sensor pulses in a pulse train must be within the normal operating range of 17-83 %. If this is exceeded, a diagnostic trouble code (DTC) will be stored in the engine control module (ECM).

HINT: Extremely diluted engine oil can result in a diagnostic trouble code (DTC) for the oil level being stored in the engine control module (ECM).

For further information about diagnostic trouble codes (DTCs), see diagnostic trouble codes (DTCs) in appropriate scan tool.