Electronics - Design and Function - 2 of 4: Diagnosis Volvo C70 II

DIAGNOSTIC FUNCTIONS

The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

DIAGNOSTIC TROUBLE CODES (DTCS)

A diagnostic trouble code (DTC) is stored if the control module detects a fault. A fault which is detected in the most recent operating cycle is defined as permanent. Other faults are defined as intermittent. If for some reason a fault disappears after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault is stored in the control module.

READING OFF THE VOLVO ON-BOARD DIAGNOSTIC (OBD) SYSTEM

Information about faults and other data can be read off using VIDA (Volvo scan tool). VIDA communicates with the control module in a standardized interface.

VOLVO ON-BOARD DIAGNOSTIC (OBD) SYSTEM

Using VIDA (Volvo scan tool) it is possible to

1. read off and erase stored diagnostic trouble codes (DTCs)
2. continuously monitor the values and status of the input and output signals for the signals
3. activate certain functions
4. read off the control module identification.

The following conditions must be met before the Volvo on-board diagnostic (OBD) system is activated

1. the ignition must be on
2. the battery voltage must be normal.

READING AND ERASING DIAGNOSTIC TROUBLE CODES (DTCS)

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

The Driver door module (DDM) and Passenger door module (PDM) have integrated diagnostics, Volvo Diagnostic, which continuously monitors itself as well as input and output signals.

A diagnostic trouble code (DTC) is stored if the control modules detect a fault. The Driver door module (DDM) and Passenger door module (PDM) can store up to 10 diagnostic trouble codes (DTCs) each.

If a fault disappears for any reason after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault remains in the control module.

READING OUT AND ERASING DIAGNOSTIC TROUBLE CODES

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

The Convertible Roof Module (CRM) has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

A diagnostic trouble code (DTC) is stored in the control module if the Convertible Roof Module (CRM) detects a fault. Every diagnostic trouble code (DTC) has a counter which records the number of cycles which have been "fault-free" since the diagnostic trouble code (DTC) was stored. A fault which is detected in each operating cycle is defined as permanent. A fault which is detected in one or more operating cycles (although not the present one) is defined as intermittent.

An operating cycle is the period from when the ignition has been off, then on for at least 10 seconds and finally off for at least 10 seconds.

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

READING OFF EXTENDED DIAGNOSTIC TROUBLE CODE (DTC) INFORMATION

This function can be used to read parameters, status identifiers and counters stored at the same time as a diagnostic trouble code (DTC). These are called frozen values.

DIAGNOSTIC VERSIONS AND COMMUNICATION METHODS

Since the end of the 1980s, the control module's diagnosis has developed from detecting simple problems and storing a small amount of information to including more complicated tests and checks.

Today a large amount of information can be read out both about the detected problem as well as parameters from the control module's input and output signals.

The following accounts for the main principles for this development.

Scheme 609

A Volvo standard was introduced (Volvo Diagnostics I) 1988 , which means diagnosis of several on-board systems (On Board Diagnostic).

This Volvo Diagnostics included

1. Store problem indicators (diagnostic trouble codes) for various components as well as delete them (check function 1).
2. Confirmation of activating components or functions (check function 2).
3. Cyclic activation of components/functions (check function 3).

A diagnostic tool (diagnostic socket with light-emitting diode) was located in the engine compartment for reading out a Volvo Diagnosis from the various control modules.

Volvo Diagnostics, the first version is found on, e. g., fuel control system LH 2.4 and ignition system EZ 116K for model 240 and 740.

VOLVO DIAGNOSTICS I - SECOND VERSION

Volvo Diagnostics, the second version, was introduced in 1991 meant that additional services were made available, such as

1. Possibility to control transfer rate for data between the control module and the diagnostic socket.
2. Individual activation of components/functions (check function 4).
3. Read in and out signals (check function 5), where every value is represented by a three-digit code.
4. Enter data (check function 6), where you could enter data via three-digit codes.

Services are introduced to varying extent on the different control modules.

The diagnostic socket with light-emitting diode is used to read out Volvo Diagnostics from the various control modules.

The tool Volvo Diagnostic Key and then Volvo System Tester were introduced to make communication easier with the control module.

Volvo Diagnostics, the second version is found on, e. g., Transmission control module (TCM)a AW 30-40/43 in model 960 and AW 50-42 in model 850.

VOLVO DIAGNOSTICS II - FIRST VERSION

Volvo Diagnostics II - first version was a new Volvo standard introduced in 1996 . This meant that control modules communicated serially in the same way, and that diagnostic functions in the different systems were designed in a similar manner.

The communication cable in the vehicle used for this communication is common to all control modules in question. The control modules are connected to the same connection in the diagnostic socket (pin 7).

The diagnostic socket is located in the passenger compartment and for certain markets it is common with the diagnostics system OBD II.

Volvo Diagnostics II, first version, was introduced in 1996 on, among others

1. Engine management system Motronic 4.4
2. Automatic transmission AW 50 42/AW 30 40/43
3. Control module Airbag SRS6.2
4. Immobilizer
5. Control module Brakes ABS 850
6. Combined instrument panel 850
7. Power seat 850/960
8. and was gradually introduced for additional systems and car models.

For certain models, the diagnostics tool for this diagnosis is still Volvo System Tester (car models from and incl. model year 1998 as well as certain systems for model year 1999).

The diagnostics tool VIDA, now replacing VADIS, is used for car models of model year 1999 and later.

Scheme 610

Volvo Diagnostics II - second version was introduced in 1999 and is a development of the first version. The major difference is that communication between the diagnostics tool and the control modules takes place via CAN-communication instead of on a communication cable.

The control modules also communicate with each other to exchange information on the CAN-net instead of via separate cables between the control modules.

This version introduced the possibility to download software to the control modules.

With the introduction of this version, the rate in the low-speed network was (LS CAN) 125 kbit/s and the rate in the low-speed network was (HS CAN) 250 kbit/s. Depending on model and model year, the speed of the network has increased with time.

Volvo Diagnostics II, second version, was introduced in model S80/S60/V70 (00-)/V70 XC (01-)/XC70/XC90 model year 1999- as well as S70/V70 (-00)/V70 XC (-00)/C70 for model year 1999 and thereafter in future models.

The diagnostics tool VIDA, now replacing VADIS, is used for car models of model year 1999 and later.

Scheme 611

Generic Global Diagnostics (GGD) is a mutually developed diagnostics concept within the Ford company.

Communication and services are similar to Volvo Diagnostics II - first version. Communication between the diagnostics tool and control modules takes place via CAN-communication. The services that can be performed are similar.

Designation of trouble codes adheres to standard ISO/DIS 15031-6.4 and consist of a letter and six characters.

The control modules also communicate on the CAN-net with each other to exchange information.

It is also possible to download other software to the control modules.

Volvo Diagnostics, fifth version, was introduced in model XC90 model year 2005 with engine B8444S (only high-speed network) and then in model S80 (07-).

The diagnostics tool VIDA, now replacing VADIS, is used for car models of model year 2005 and later.

Scheme 612

The control module's diagnostics can perform and present the following using a connected diagnostics tool

1. Store malfunction indicator (diagnostic trouble codes) and in certain cases activate warning light or show text message. Counter that indicates how frequent the malfunction is Status indicators for the diagnostic trouble code test. Frozen values that were generated when malfunction was detected for the first time.
2. Store information about the nature of the malfunction: Counter that indicates how frequent the malfunction is Status indicators for the diagnostic trouble code test. Frozen values that were generated when malfunction was detected for the first time.
3. Erase information about malfunction and its information.
4. Present values (parameters) for different connected input signals and output signals from, e. g., components as well as other calculated values.
5. Present part number, version number, component number, etc. for both software and hardware.
6. Present and change certain special customer settings and configurations.
7. Trigger/control (activate) the connected output signals.
8. Start special built-in check programs/tester such as, e. g., calibrations of gear position sensor, quick-test of tank system.
9. Access check to limit access to certain parameters and functions. Accessible first after unlocking with, e. g., PIN-code.

Exactly what each control module's diagnostics can perform depends both on model year and system.

DIAGNOSTIC TROUBLE CODES (MALFUNCTION INDICATOR)

1. see «MALFUNCTION DETECTING»(ref-488592-S11087820652012081400000)
2. see «CONDITIONS FOR DIAGNOSIS TO FIND A MALFUNCTION»(ref-488592-S40080487812012072500000)
3. see «DRIVING CYCLE/OPERATION CYCLE»(ref-488592-S05108345652012072500000)
4. see «EMERGENCY MODE, BACK-UP MODE "LIMP-HOME"»(ref-488592-S08371062752012072500000)
5. see «CLASSIFICATION OF DIAGNOSTIC TROUBLE CODES»(ref-488592-S06657545562012072500000)
6. see «DESIGNATION OF TROUBLE CODES»(ref-488592-S37230087702012072500000)
7. see «STATUS IDENTIFIER»(ref-488592-S27195835462012072500000)
8. see «COUNTER»(ref-488592-S11448149752012072500000) =
9. see «FROZEN VALUES»(ref-488592-S37658985822012072500000)
10. see «ERASING DIAGNOSTIC TROUBLE CODES»(ref-488592-S35064930122012072500000)
11. see «READINESS MONITOR (CERTAIN MARKETS ONLY)»(ref-488592-S12047061892012072500000)

ERASING DIAGNOSTIC TROUBLE CODES

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function. Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

When erasing diagnostic trouble codes, the diagnostic trouble code's counter, status identifier as well as frozen values are also erased.

For certain systems, stored adaptions may also be reset when erasing.

Scheme 613

All control modules' diagnostics require that some form of driving cycle or operation cycle is run for diagnostics to be considered as complete. The terms driving cycle or operation cycle appear, these mean the same, they are only different designations.

Example

The illustration shows an example of a driving cycle or operation cycle. The vehicle is started and driven (Start) , is stopped sometime and the ignition is turned off (Stop) . When the ignition is turned on again (Start) a new driving cycle starts.

A new driving cycle or operation cycle usually starts every time the ignition is turned on, which means that you should turn on the ignition, turn off the ignition, and then turn on the ignition again.

However, the condition varies from control module to control module, there are also, e. g., speed and temperature conditions, before a driving cycle or operation cycle is considered to be complete.

When a malfunction is detected and then is confirmed as a real malfunction and is stored, various counters are also stored, indicating how frequent the malfunction is. These counters use driving cycles or operation cycles as basis for updating the counters' values.

DESIGNATION OF TROUBLE CODES

The diagnostics tool VIDA (Volvo scan tool) shows the diagnostic trouble code in plain text according to the following example

TCM-001F Speed sensor Signal missing Permanent malfunction

This diagnostic trouble code consists of the following parts

1. Prefix for control system in question ( TCM ) to show what system the diagnostic trouble code belongs to. * If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage. If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections.
2. Diagnostic trouble code number ( 001F ) to decide which diagnostic trouble code is stored. Number of digits in the diagnostic trouble code number may vary. *, ** If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage. If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections. NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
3. Title ( Speed sensor ) is a text that shows to which component/function the diagnostic trouble code refers. * If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage. If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections. NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
4. Qualifier ( Signal missing ) is used to show how the control module has perceived the signal from, e. g., the sensor, or how it detected the monitored function. In this case, the control module has perceived that the signal is missing. There a re a number of other qualifiers for, e. g., too high signal, incorrect signal, too high flow, too low flow, etc. *, **. If the qualifier is, e. g., "Too high signal", the control module interprets that the signal from the sensor is too high. This may mean that, e. g., the voltage is too high, current is too high, frequency is too high, or the pulse ratio (% duty) is too high, all depending on which type of signal it is. Malfunction causes may be, e. g., open circuit or short-circuiting to voltage. If the qualifier is "Too low signal", the control module interprets that the signal from the sensor is too low. Malfunction causes may be, e. g., open circuit, short-circuiting to ground, contact resistance in connections. NOTE: Information about which type of signal that the control module detects and what conditions are required to detect that a malfunction is found again in the diagnostic trouble code information.
5. Status ( Permanent malfunction ) to show the malfunction's status, that is, if the malfunction has been detected in the present driving cycle or not. There are two different status texts, permanent or intermittent. When the control module's diagnosis cannot decide the malfunction's status, the diagnostic trouble code is shown without status text. *

* When reading out diagnostic trouble codes using diagnostic socket with light-emitting diode, you get a three-digit flash code. Then this code is translated to a diagnostic trouble code text using the service information.

For example, if the control module flashes the code 1-2-3 from Engine control module (ECM), it can be translated to, e. g., diagnostic trouble code 1-2-3 Engine temperature sensor. Volvo Diagnostic Key and Volvo System Tester translate these flash codes directly to plain text (add a title). In these diagnostic systems it is not possible to show qualifier or status.

** For systems with diagnostic version called Generic Global Diagnostics (GGD) (adheres to standard ISO/DIS 15031-6.4) the diagnostic trouble code number consists of a letter and six characters. The letter alternatives are B, C, P and N, which means Body, Chassis, Powertrain and Network and indicate to which "function" in the vehicle the diagnostic trouble code belongs. The six following characters may consist of both letters (A-F) and digits (0-9) and indicate the component to which the malfunction refers as well as what type of malfunction. See following example.

BCM-C006A16 Multi-axial acceleration sensor. General electric malfunction. Too low voltage

CLASSIFICATION OF DIAGNOSTIC TROUBLE CODES

In principle, malfunctions can be classified in two categories, intermittent or permanent.

Permanent malfunctions.

The easiest malfunctions to identify and confirm as a malfunction are the permanent malfunctions. A permanent malfunction is a malfunction when something has "broken" and remains like that until it is repaired.

Intermittent malfunctions.

The intermittent malfunctions are, as opposed to the permanent malfunctions, are both difficult to identify and confirm. The malfunction exists but is neither active nor present all the time. The malfunction comes and goes briefly under very rare conditions.

For the intermittent malfunctions, the degree of intermittence can also be determined, that is, how intermittent the malfunction is (how often/seldom the malfunction appears).

HINT: For assessment of intermittence, stored counters are used together with the diagnostic trouble code.

Common permanent malfunction causes are

1. Open circuits or short-circuits on cables or in connectors caused by mechanical damage, vibrations, corrosion, oxidation, moisture, etc.

Common intermittent malfunction causes are

1. Loose connections or contact resistance caused by vibrations, corrosion, oxidation, moisture, etc.
2. Brief short-circuits to both ground and voltage caused by damage to cables, moisture in connectors, etc.
3. Electro-magnetic interference.

Malfunction causes may be both electrical, mechanical or related to software.

Intermittent malfunctions (or malfunctions that occur under unknown conditions) may also be malfunctions that only occur during certain operation or ambient conditions.

E. g., that the window or seat for some reason jams in its end-position when using automatic function, or that the climate control unit supplies poor heat in a certain position when it rains outside.

CONDITIONS FOR DIAGNOSIS TO FIND A MALFUNCTION

For the control module's self-diagnosis of a component or function to start and run (one or several times) special conditions must be fulfilled. Conditions for diagnosis varies depending on which component or function is to be monitored. When the diagnosis has started and is run, the signal, value or function must go above or below the limit value for the control module to detect a malfunction.

Example of conditions for the control module to start the diagnosis/test

1. Engine speed higher than 500 RPM.
2. Ignition position II.
3. Speed above 40 km/h.
4. 4th gear selected.

Example of limit values for detecting malfunction

1. Direct voltage from outside temperature sensor lower than 0.495 V for a time longer than 1 second.
2. After the engine has run for approx. 10 minutes, the control module receives an unchanged signal from the oil temperature sensor even though the signal should have changed according to a set pattern.
3. Malfunction shall be active (permanent) for at least 2 driving cycles.

Example

Scheme 614

The illustration shows an imagined scenario when a malfunction occurs in a circuit for a signal.

First the signal varies normally during driving. The diagnostic trouble code test starts after some time (5), is then run cyclically in a pre-defined pattern and monitors the signal. Limit values for monitoring to consider the signal as incorrect is a voltage lower than 0.50 V (2) or higher than 4.85 V (1). An open circuit occurs in the circuit and the signal becomes 0 V (4). Monitoring detects this, waits so that the malfunction is confirmed and then stores a diagnostic trouble code (6).

Scheme 615

If the diagnostic trouble code test (5) starts after the malfunction (4) occurs, then monitoring will detect the malfunction fist when the test starts. Then monitoring waits so that the malfunction is confirmed and then stores a diagnostic trouble code (6). If you want the control module to detect a malfunction in the vehicle, you have to make sure that the control module's diagnostic trouble code test starts or is started.

HINT: If a malfunction occurs which has not yet been detected by the control module's monitoring, since the diagnostic trouble code test has not started, the vehicle may still exhibit a symptom.

Note. Conditions for diagnosis are described in the diagnostic trouble code information for every diagnostic trouble code.

Most diagnosis (at least non-emission-related diagnosis) are repeated periodically during the driving cycle, and every time they are repeated, a test is run that either results in a malfunction being detected or no malfunction being detected.

To enable the emission-related diagnosis to be completed and the diagnostic trouble code to be confirmed (with MIL-light activated as a result), several driving cycles in a row must be completed with a detected malfunction.

To enable the non-emission-related diagnosis to be completed (at least once), in principle the start conditions must be fulfilled for a certain time (from fractions of a second to a number of seconds).

Certain diagnoses require a completed driving cycle (e. g., ignition on, ignition off, and ignition on again) for the diagnosis to be considered as complete. Other diagnoses requires several other conditions to be fulfilled, e. g., with regards to

1. vehicle speed
2. engine coolant temperature (ECT)
3. time since start
4. different load and engine speed relationships in the same trip
5. a certain event (for example, that the component operates).

HINT: To assess if a test/diagnosis for the diagnostic trouble code is started or completed, status identifiers can be used. Turning off the ignition and then turning it on again often results in start of a new driving cycle/operation cycle, which results in update of status identifiers.

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

Emissions related diagnostic functions

Control modules that have and control emission-related components or functions, e. g., Engine control module (ECM) and Transmission control module (TCM), check that emission-related systems work. These systems are checked by running a diagnostic function. The diagnostic function checks the included components and that the function itself works in the system.

Lighting the malfunction indicator lamp (MIL)

In the event of emissions related diagnostic trouble codes (DTCs), a counter counts down to determine when to light the malfunction indicator lamp (MIL). The conditions for lighting the malfunction indicator lamp (MIL) vary depending on which diagnostic trouble code (DTC) is stored.

Note. If a malfunction becomes intermittent or the malfunction disappears, then the MIL-light turns off first after 3 driving cycles in a row are completed with malfunction detection.

Self-erasing of emission-related diagnostic trouble codes

After 40 driving cycles without detected malfunction with start of cool engine, where the engine temperature (coolant temperature) increases more than 5 °C (approx. 9 °F) and the final temperature is above approx. +71 °C (159.8 °F), then the diagnostic trouble code is erased. Diagnoses (diagnostic trouble code tests) for misfire and fuel adaptions require 80 driving cycles. These driving cycles are defined as a "warm-up cycle".

STATUS IDENTIFIER VOLVO DIAGNOSTICS II

The following identifiers are available (showed values apply until updated with a new read-out)

1. SB 01 Diagnostic trouble code test run in progress.
2. SB 02 Diagnostic trouble code test run at least once during current driving cycle.
3. SB 03 Sporadic/single malfunctions found the last time diagnostic trouble code test was run during current driving cycle/operation cycle.
4. SB 04 Sporadic/single malfunctions found at least once during current driving cycle.
5. SB 05 Request light warning light/text message due to detected malfunction.
6. SB 06 Diagnostic trouble code test blocked due to malfunction found by another diagnostic trouble code test.
7. SB 08 Malfunction detection counter, current value.
8. SB 09 Malfunction detection counter, maximum value reached some time during current operation cycle.

Abbreviation SB is from the English 'Status Bit'.

Scheme 616

The upper graph shows a varying signal value. If the signal value exceeds a max. value, which is considered a malfunction by the control module, then a sporadic malfunction is registered, that is, a malfunction is about to occur. Then the grey-marked surface indicates the signal considered to be incorrect.

The text below uses the term Driving cycle, which may also be called Operation cycle.

Note. If the diagnostic trouble codes are erased, the status identifiers are also erased

SB01 Diagnostic trouble code test run in progress (second paragraph from top).

Shows if the diagnostic trouble code test runs or not right now (in current driving cycle). It is only when the test runs that the control module can detect malfunctions and generate diagnostic trouble codes.

Grey-marked surface means that the test runs and can detect a malfunction if it occurs. The surface is "dashed", showing that when the diagnostic trouble codes runs, it runs in a cyclic, pre-determined pattern.

Status identifier 03 and 04 shows if a malfunction is detected or not. In this case, a malfunction is detected 3 times, see status identifier #03 in (Scheme 616).

Status alternative when reading out is Yes (test runs now) or No (test is not run now).

SB02 Diagnostic trouble code test run at least once during current driving cycle (third graph from the top).

Shows if the diagnostic trouble code test has been run or not during the current driving cycle. If it has been possible for the control module to detect malfunctions and generate diagnostic trouble code any time during the current driving cycle.

Grey-marked surface means that the diagnostic trouble code test has been run at some time. If the diagnostic trouble code test has been run at some time in this driving cycle, status will always be Yes and remain so until the ignition is turned on off and a new driving cycle starts. When a new driving cycle starts, status identifiers are "reset" and is initially No.

Status identifier 03 and 04 shows if a malfunction is detected or not.

Status alternative when reading out is Yes (test completed) or No (test not completed).

SB03 Sporadic/single malfunctions found the last time diagnostic trouble code test was run during current driving cycle (fourth graph from the top).

A sporadic malfunction (intermittent malfunction) has been detected 3 times the last time the diagnostic trouble code test was run during current driving cycle. During the diagnostic trouble code test run the last time (see status identifier #01 in (Scheme 616) ) a malfunction has been detected 3 times.

Status alternative when reading out is Yes (sporadic malfunction found) or No (no sporadic malfunction found).

Note. When the control module detects the malfunction for the first time(status identifier 03 and 04), a diagnostic trouble code has not yet been stored (see last graph in (Scheme 616) ). It is first when the malfunction detection counter 08 reaches a certain value that the control module considers that a real malfunction exists (a confirmed malfunction) and the diagnostic trouble code is stored.

SB 04 Sporadic/single malfunctions found at least once during current driving cycle (fifth graph from the top).

A sporadic malfunction (intermittent malfunction) has been detected at some time during current driving cycle. Grey. marked surface means that a malfunction has been detected at some time.

If the diagnostic trouble code test has been run at some time in this driving cycle, status will always be Yes and remain so until the ignition is turned on off and a new driving cycle starts. When a new driving cycle starts, status identifiers are "reset" and is initially No. Status identifier 03 and 04 shows if a malfunction is detected or not.

Status alternative when reading out is Yes (test has been run earlier) or No (test has not been run).

SB 05 Request light warning light/text message due to detected malfunction (sixth paragraph from the top).

Information that diagnostic trouble code activates a warning light or text message in driver information module. In this case, lighting of warning light is requested when the diagnostic trouble code has been confirmed and stored.

Status alternative when reading out is Yes (request performed) or No (no request).

SB06 Diagnostic trouble code test blocked (seventh graph from top).

Information that diagnostic trouble code test is turned off as a result of another malfunction and diagnostic trouble code is generated where the root cause is detected. If this in turn results in subsequent malfunctions, it prevents generation of subsequent diagnostic trouble codes. In this case, the diagnostic trouble code test is not blocked.

Status alternative when reading out is Yes (diagnostic trouble code test blocked) or No (diagnostic trouble code test not blocked).

SB08 Malfunction detection counter, current value (eight graph from top).

When a sporadic malfunction is detected by the control module the malfunction detection counter counts up as long as the malfunction exists.

When the malfunction no longer exists the counter counts down again. This is the basis for the control module's decision to store the diagnostic trouble code and the diagnostic trouble code is stored in the vehicle first when the counter reaches a certain max. value. This max. value varies between different diagnostic trouble codes.

Count rate of the counter is controlled as long as the malfunction exists before it causes customer symptom. The counter is used to decide if it is a real malfunction that has occurred and that has existed for some time. It is the control module's way of confirming the diagnostic trouble code, that is, confirming that a real malfunction exists.

SB09 Malfunction detection counter, max. value during current operation cycle

Shows max. value that status identifier 08 has reached during current driving cycle. When a new driving cycle starts, the counter is "reset".

STATUS IDENTIFIER GENERIC GLOBAL DIAGNOSTICS (GGD)

The following identifiers are available (showed values apply until updated with a new read-out)

1. SB 00 Malfunction found the last time that the diagnostic trouble code test was run during current driving cycle
2. SB 01 Malfunction found at least once during the current driving cycle
3. SB 02 Malfunction found at least once during the current and previous driving cycles
4. SB 03 Malfunction found recently since erasing of diagnostic trouble codes
5. SB 04 Diagnostic trouble code test run at least once since erasing of diagnostic trouble codes
6. SB 05 Malfunction found at least once since erasing of diagnostic trouble codes
7. SB 06 Diagnostic trouble code test run at least once during current operation cycle.
8. SB 07 Request light warning light/text message due to detected malfunction.

Scheme 617

The upper graph shows a varying signal value. If the signal value exceeds a max. value, which is considered a malfunction by the control module, then a sporadic malfunction is registered, that is, a malfunction is about to occur. Then the grey-marked surface indicates the signal considered to be incorrect.

The text below uses the term Driving cycle, which may also be called Operation cycle. The order of status identifiers in illustration and in the list below are presented as they belong to each other, not in numerical order.

Note. If the diagnostic trouble codes are restored, the status identifiers are also restored

Graph A Diagnostic trouble code test active

Shows if the control module's diagnostic trouble code test is active or not. The blue surface indicates when the test is active. The surface is "dashed", which shows when the diagnostic trouble code test runs it runs in a cyclically pre-determined pattern. Not included as a status identifier.

Graph B Malfunction active

Shows if the malfunction in the vehicle is active or not. The red surface indicates when the malfunction is present (active). Not included as a status identifier.

Graph C Counter 6 malfunction detection (C#6)

The counter counts the number of internal detections of the malfunction that have been performed for the diagnostic trouble code. Not included as a status identifier. When this counter reaches value +127 the control module considers the malfunction to be active right now.

When the counter is at value -128, the malfunction is not active. The value is reset for every new driving cycle.

If the value increases towards +127, the control module has detected a malfunction and for every internal test the value is counted up. When the malfunction no longer exists, the control module counts down to minimum -128.

The value on the control module can only be changed when it has started the test for the diagnostic trouble code. How big each step is that the control module counts up or down the value by to reach the limits +127 or -128 may vary between control modules. Limits +127 and -128 are pre-defined limits in the control module.

In the graph, the counter first counts down to -128 when the diagnostic trouble code test starts (graph A). When a malfunction occurs (graph B) and the diagnostic trouble code test detects the malfunction, first the counter's value is reset to 0, then it scrolls up to +127. Only then the malfunction is considered to exist. If the malfunction disappears and the diagnostic trouble code test is active, the counter counts down to -128.

SB 06 Diagnostic trouble code test run at least once during current operation cycle

Shows if the control module has performed diagnostic trouble code test for this diagnostic trouble code in current driving cycle. When the diagnostic trouble code test starts and counter 6 (malfunction detection) counts down to -128 (no malfunction found) or up to +127 (malfunction found), the control module considers that diagnostic trouble code test has been run.

Yellow-marked surface means that diagnostic trouble code test is not yet run.

Status alternative when reading out is Run or Not run.

SB 00 Malfunction found the last time that the diagnostic trouble code test was run during current driving cycle

Shows if the control module detects the malfunction right now. It is only when the test runs that the control module can detect malfunctions and generate diagnostic trouble codes. A malfunction has been detected 2 times during the current driving cycle. Note that only when counter 6 (malfunction detection) reaches the value +127 is it considered to be a malfunction. When the value gas dropped from +127 to 0, it is considered that there is no longer a malfunction.

Status alternative when reading out is Yes (malfunction detected right now) or No (no malfunction detected right now).

SB 01 Malfunction found at least once during the current driving cycle

Shows if the control module has detected the malfunction anytime during the current driving cycle. It is only when the test runs that the control module can detect malfunctions and generate diagnostic trouble codes. The diagnostic trouble code test has started and a malfunction has been detected at least 1 time during the current driving cycle.

Status alternative when reading out is Yes (malfunction found) or No (malfunction not found).

This status identifier is generated at the same time as status identifier SB00 and will remain in status Yes for the rest of the current driving cycle. At start of a new driving cycle, it has changed to status No until a malfunction is detected again.

SB 05 Malfunction found at least once since erasing of diagnostic trouble codes

Shows if the control module has detected the malfunction during earlier driving cycle. A malfunction has been detected at least 1 time since the diagnostic trouble code was erased the last time.

Status alternative when reading out is Yes (malfunction found) or No (malfunction not found).

This status identifier is generated at the same time as status identifier SB 00 and will remain in status Yes until diagnostic trouble codes are erased once again.

SB 04 Diagnostic trouble code test run at least once since erasing of diagnostic trouble codes

Shows if the control module has performed diagnostic trouble code test for this diagnostic trouble code in current and/or earlier driving cycle since the diagnostic trouble code was erased the last time. This means that if diagnostic trouble code test has been run after erasing of diagnostic trouble codes, it will remain in Run until diagnostic trouble codes are erased once again.

Yellow-marked surface means that diagnostic trouble code test has been run.

Status alternative when reading out is Run or Not run.

This status identifier is generated at the same time as status identifier SB 06.

SB 07 Request for lit warning light/text message

Information about the diagnostic trouble code activates a warning light or text message. In this case, lighting of the warning light is requested when a diagnostic trouble code is stored.

Status alternative when reading out is Yes (request performed) or No (no request).

SB 02 Malfunction found at least once during the current and previous driving cycles

Pending not yet confirmed diagnostic trouble code.

Status alternative when reading out is Yes (malfunction found but not confirmed) or No (no malfunction found).

This status identifier is generated at the same time as status identifier SB 00 is generated for the first time and will remain in status Yes until certain driving cycle conditions are fulfilled and no malfunctions are detected. After a certain number of driving cycles without detected malfunction, it returns to status No. Number of driving cycles required depends on the system.

SB 03 Malfunction found recently since erasing of diagnostic trouble codes

Confirmed diagnostic trouble code.

Status alternative when reading out is Yes (malfunction found and confirmed) or No (no malfunction found).

This status identifier is generated at the same time as status identifier SB 00 is generated for the first time and will remain in status Yes until certain driving cycle conditions are fulfilled and no malfunctions are detected. After a certain number of driving cycles without detected malfunction, it returns to status No. That is, if a malfunction becomes intermittent and no longer is detected, the status will change to No. Number of driving cycles required depends on the system.

Note. For emission-related control system, this status identifier is generated to status Yes (Malfunction found and confirmed), first after status identifier SB02 has had status Yes (Malfunction found but not confirmed) for 2 driving cycles in a row with malfunction detected.

PRACTICAL USE OF DIAGNOSTICS

There are several ways to decide if the malfunction is active right now or not as well as when the malfunction occurred

1. Read off the diagnostic trouble code's counter, status identifier and frozen values. By interpreting these you can find out when the malfunction was stored, how often the malfunction has occurred (intermittence) and what the driving conditions were when the malfunction was stored.
2. Read off a parameter for component/system and decide if the value is correct or not. By, e. g., manually affecting the sensor or the switch, you can decide immediately if the parameter (signal) with its circuit is correct.
3. Trigger a component (activate) and decide if the component/function is affected or not. By triggering, e. g., the relay and listening for its clicking sound or the function which is to be affected, it is possible to decide immediately if the component is correct.
4. Decide if the vehicle shows any symptom (malfunction). If the vehicle no longer shows the symptom, one may suspect that the malfunction no longer is active.

The following accounts in detail for some of the above.

TO DECIDE DIAGNOSTIC TROUBLE CODE TEST'S STATUS

By reading out the diagnostic trouble code with associated status identifier, then status for the diagnostic trouble code test that detects the malfunction and generates the diagnostic trouble code, is obtained.

Example 1, Permanent malfunction

Status identifier

The diagnostic trouble code test has been run in both current driving cycle and in earlier driving cycles. Malfunction has been detected both in current driving cycle and in previous driving cycle, which indicates that the malfunction is active right now. The control module has requested lighting of the warning light.

Conclusion: Permanent malfunction.

Assessment: Very good chance to repeat the customer symptom and thus succeed with troubleshooting, as the malfunction has been found in current and in previous driving cycle. Since the malfunction has been detected during the present run cycle, it does not really matter for troubleshooting if the malfunction has been detected in all previous driving cycles or not. If this information is supplemented with the counters' values you can decide how "permanent" the malfunction is.

If the vehicle is stationary, e. g., with the ignition on, this means that the test runs directly when the ignition is turned on. This makes it easier to both fins the malfunction and to verify that the malfunction cause has been take care of.

Example 2, Unknown status

Status identifier

The diagnostic trouble code test has been run in previous run cycles but not in current driving cycle. Malfunction has been detected in previous run cycle, but not in current driving cycle since the test has not started. Warning light is on.

Conclusion: Unknown status

Assessment: Since the test has not started in the current driving cycle it is not possible to decide if the malfunction is "active" right now. First read the diagnostic trouble code information and try to obtain conditions so that the test is started and run, which enables detection of the malfunction. If the malfunction is detected, chances are very good to repeat the customer symptom, and thus succeed with troubleshooting as the malfunction has been found in the current driving cycle.

If the malfunction was not detected even though conditions are fulfilled, then chances are less good to repeat the customer symptom, and thus succeed with troubleshooting as the malfunction has not been found in the current driving cycle.

TOOLS FOR DIAGNOSTICS

Tools used for troubleshooting and diagnostics are divided into two different types, tools for Off Board Diagnostic (diagnostics outside the vehicle) or On Board Diagnostic (diagnostics system in the vehicle) where the control module's diagnosis is used.

There are several tools used for Off Board Diagnostics, a few intended for diagnosis of a control module and its systems are mentioned in this document.

Note. There are control modules with integrated diagnosis, where read-out of diagnosis only is possible with a built-in "tool". This applies to, e. g., climate control module MCC for model S70/V70/C70, where read-out takes place via light-emitting diode on the front of the panel. For, e. g., audio unit HU 1205 for model S40/V40, the audio unit is not connected to the diagnostics socket in the vehicle. All diagnostics as well as other settings are controlled directly by menus in the display.

TOOLS FOR OFF BOARD DIAGNOSTICS

Troubleshooting instrument ("Carpenter's toolbox")

Scheme 618

This troubleshooting instrument ("Carpenter's toolbox") (998-8195) is connected in parallel with the fuel control module and the vehicle's cable harness. Using the control on the box itself, you choose which values that the analogue display is to show.

The box also contains two light-emitting diodes, one green and one red which are turn on/off, e. g., at released or pressed down accelerator (check of throttle switch).

A number of different adapters made it possible to connect to different control modules.

Example of fuel systems where the tool can be used

1. LH-Jetronic, B200/230-engines for model 200/700.
2. LE/LU-Jetronic, for model 360.
3. Fenix, model 400.
4. Motronic, model 740/760 Turbo.

Volvo System Tester - parallel connection

Scheme 619

Volvo System Tester - parallel connection was introduced for model year 1986, as a troubleshooting instrument where you connected in parallel between the control module and the cable harness.

Volvo System Tester measured input and output signals in analogue mode and signals were then shown in Volvo System Tester. It was also possible to detect intermittent malfunctions.

With Volvo System Tester connected, it was possible to

1. Reading off values of signals such as coolant temperature, voltage on heated oxygen sensor, etc.
2. Monitor certain signals and compare with pre-programmed values as well as register and store deviations.

A number of different adapters made it possible to connect to different control modules.

Thus, at parallel connection, diagnosis is performed of Volvo System Tester.

TOOLS FOR ON BOARD DIAGNOSTICS

Test diode

Scheme 620

The test diode (999-5280) is used to "flash" diagnostic trouble codes. The test diode is connected to a connector (located in engine compartment on certain vehicles) and using this, the control module "flashes" diagnostic trouble codes from certain ignition systems.

The test diode can also for some vehicles be used to check the CO-content from the engine. Then the test diode is connected to another connector than when reading out diagnostic trouble codes.

1. Light-emitting diode
2. Connection to voltage feed.
3. Connection control module for reading out diagnostic trouble codes
4. Connection control module for checking CO-content.

Example of ignition systems where diagnostic trouble codes can be read out

1. Rex, model 240 with engine 230K (4 diagnostic trouble codes).
2. EZ 102K, model 760 Turbo-84 engine B23 FT (5 diagnostic trouble codes).
3. EZ 115K, model 760/780 engine B280E/F (6 diagnostic trouble codes).

Diagnostic socket with light-emitting diode

Scheme 621

A diagnostic socket with light-emitting diode was located in the engine compartment for reading out Volvo Diagnostics from the various systems. It was introduced for model year 1988. Every control module in the vehicle was connected to one of the diagnostic socket's six positions.

As the number of control modules in the vehicles increased and one diagnostics socket was not enough for all control modules, later on two diagnostics sockets were introduced, marked A and B.

For communication with a certain control module, the portable connector is connected to the control module's position in the diagnostics socket. Then the different checking functions are activated by pressing down the diagnosis button a different number of times.

When the button is pressed down, the cable to the control module is grounded, the ground pulse indicates to the control module that communication is initiated and the diode is lit. Then you release the button. Then control module then answers by grounding the cable in different patterns, making the diode turn on and off. Then these "flash codes" must be translated.

Volvo Diagnostics I, the first version is found on, e. g., fuel control system LH 2.4 and ignition system EZ 116K for model 240 and 740.

This diagnostics socket is found in car models 240, 440/460, 740, 940/960 and 850 until model year 1995. For the 400-model, this diagnostics socket is still used after model year 1995.

Volvo Diagnostic Key

Scheme 622

All communication performed using the diagnostics socket with light-emitting diode requires both knowledge about which commands are to be sent as well as how flashes from the control module should be interpreted.

Volvo Diagnostic Key - plain text reading was introduced for model year 1991 to facilitate reading out, interpreting and entering flash codes when communicating.

The tool is connected to the diagnostics socket/sockets with the light-emitting diode and sends, via menu selections, the right commands, then translates the control module's answer (light-emitting diode's flashes) to plain text.

Volvo System Tester

Scheme 623

Serial communication

When non-standardized serial communication was introduced in 1991/1992, Volvo System Tester was developed to communicate serially with the control modules. This was so that the new possibilities with serial communication could be used, that is, use the built-in diagnosis in the control module (On Board Diagnostic).

In connection with the introduction of Volvo Diagnostics II, model year 1996, the Volvo System Tester was also developed for this standard.

Plain text reading

Volvo System Tester was also developed to handle the same functionality as Volvo Diagnostic Key, that is, to work as a plain text reader.

Volvo System Tester can be connected to diagnostic socket (OBD II) as well as to diagnostic socket with light-emitting diode via an adapter.

VADIS - Volvo Aftersales Diagnostic and Information System

Scheme 624

At the end of the 1990s, VADIS was introduced as diagnostics tool. Volvo System Tester was first used as communication tool between the vehicle and PC, thereafter Volvo Communication Tool 2000 (VCT2000).

For a time both tools were used, depending on which system and model year you worked with. From 2005, VADIS is replaced by the tool VIDA.

VIDA - Vehicle Information & Diagnostic for Aftersales

Scheme 625

During 2005, VADIS was replaced by VIDA as the mandatory tool for diagnostics, among other things. Volvo Communication Tool 2000 (VCT2000) is used as communication tool between the vehicle and PC.

Scheme 626

Beginning in 2007, VCT2000 will be replaced by DiCE (Diagnos Communication Equipment).

DIAGNOSTIC FUNCTIONS, PASSENGER DOOR MODULE (PDM)

The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

A diagnostic trouble code (DTC) is stored if the control module detects a fault. The passenger door module (PDM) can store up to 10 diagnostic trouble codes (DTCs).

If a fault disappears for any reason after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault remains in the control module.

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

DIAGNOSTIC FUNCTIONS, DRIVER DOOR MODULE (DDM)

The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

A diagnostic trouble code (DTC) is stored if the control module detects a fault. The driver door module (DDM) can store up to 10 diagnostic trouble codes (DTCs).

If a fault disappears for any reason after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault remains in the control module.

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

A diagnostic trouble code (DTC) is stored if the control module detects a fault. The driver information module (DIM) can store up to 10 diagnostic trouble codes (DTCs).

If a fault disappears for any reason after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault remains in the control module.

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

A diagnostic trouble code (DTC) is stored if the control module detects a fault.

If for some reason a fault disappears after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault is stored in the control module.

In certain cases the faulty signal is replaced with a substitute value or certain functions are limited. Any diagnostic trouble codes (DTCs) and information stored in the control module memory can be read out using VIDA (Volvo scan tool).

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function.

Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

Note. Certain functions are unavailable until the diagnostic trouble codes (DTCs) have been erased.

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, use VIDA (Volvo 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. see «LEAK DIAGNOSTICS, ORIGINAL VERSION»(ref-488592-S40101933602012072500000)
2. see «LEAK DIAGNOSTICS, IMPROVED VERSION»(ref-488592-S28660905662012072500000)

CAMSHAFT DIAGNOSTICS (CVVT)

See CAMSHAFT DIAGNOSTICS (CVVT) .

MISFIRE DIAGNOSTIC

See MISFIRE DIAGNOSTIC .

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, use VIDA (Volvo 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. see «LEAK DIAGNOSTICS, ORIGINAL VERSION»(ref-488592-S40101933602012072500000)
2. see «LEAK DIAGNOSTICS, IMPROVED VERSION»(ref-488592-S28660905662012072500000)

HEATED OXYGEN SENSOR (HO2S) DIAGNOSTIC

See HEATED OXYGEN SENSOR (HO2S) DIAGNOSTIC .

THREE-WAY CATALYTIC CONVERTER DIAGNOSTICS

See THREE-WAY CATALYTIC CONVERTER (TWC) DIAGNOSTICS .

FUEL PRESSURE REGULATION, DIAGNOSTICS

See FUEL PRESSURE REGULATION, DIAGNOSTICS .

CONDITIONS FOR DIAGNOSIS

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

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

1. vehicle speed
2. engine coolant temperature
3. time since start
4. different load and engine speed relationships in the same trip
5. a certain event.

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

EMISSIONS RELATED DIAGNOSTIC FUNCTIONS

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

DIAGNOSTIC TROUBLE CODE MEMORY

When the engine control module detects a fault, a diagnostic trouble code with qualifier and status is stored in the control unit's diagnostic trouble code memory. Fault code storage has four status levels. When the engine control module detects a fault, the diagnostic trouble code is stored with the status. If the fault persists the next time diagnostics is performed, diagnostic trouble code status switches to. At that time, the diagnostic trouble code will appear during normal DTC readout in VIDA (Volvo scan tool). If the fault is still active during the next operating cycle, the diagnostic trouble code receives the status. If the diagnostic trouble code causes the malfunction indicator lamp (MIL) to illuminate, that process starts now. For more information, see LIGHTING THE MALFUNCTION INDICATOR LAMP (MIL) below.

If an existing fault disappears and does not return, the engine control module stores the code with the status. In this status, the diagnostic trouble code remains until the engine control module is cleared of diagnostic trouble codes or the power to it is cut off.

HINT: A diagnostic trouble code with the status can be read in VIDA (Volvo scan tool) using extended DTC readout. This is often useful when explaining a customer-reported symptom that occurred some time ago.

LEAK DIAGNOSTICS, IMPROVED VERSION

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 (Volvo scan tool) 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 (Volvo scan tool), certain different conditions apply. See relevant information about these, available with starting Quick test fuel tank system in VIDA.

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.

The front heated oxygen sensor (HO2S) is a linear type and functions with current control. Therefore it is 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 center heated oxygen sensor (HO2S) (certain markets only) is also binary. It works in the same way as previous heated oxygen sensors (HO2S).

The engine control module (ECM) checks the heated oxygen sensors (HO2S) when the conditions for the diagnostic have been met.

The following faults can be registered by the control module

1. Electrical faults in circuits for the actual heated oxygen sensors (HO2S) and in their preheating
2. Adaptation. The control module checks that the long-term fuel trim is not higher or lower than the pre-defined values
3. Heated oxygen sensor (HO2S) dynamics. The control module checks that the switch time between rich and lean mixture is not too long.

THREE-WAY CATALYTIC CONVERTER (TWC) DIAGNOSTICS

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 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 is upstream of the converter and one is 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 evaluate the efficiency of the three-way catalytic converter (TWC) one uses a deviation added to the lambda signal.

This means that 8 to 15 minutes after the engine is started (depending on the market) catalytic converter diagnostics start.

The process is as follows

A deviation is added to the lambda signal and the engine control module (ECM) is allowed to correct this.

The deviation switches between positive and negative values so that the fuel/air mixture switches between rich and lean.

A counter registers the number of switches occurring while the diagnostic is taking place.

If the rear heated oxygen sensor (HO2S) registers a large number of switches exceeding a parameter, a diagnostic trouble code (DTC) for three-way catalytic converter (TWC) efficiency will be stored.

If the parameter is not exceeded the three-way catalytic converter (TWC) is deemed to be operating well.

Note. In a poorly operating three-way catalytic converter (TWC) the switches caused by the deviation will quickly exceed the parameter. This is because the exhaust gases in principle pass straight through the three-way catalytic converter (TWC) without being cleaned. If the three-way catalytic converter (TWC) is operating well the switches will be slower as it takes a longer time for the variations to make themselves felt.

LEAK DIAGNOSTIC UNIT (CERTAIN MARKETS ONLY)

The function of the leak diagnostic unit is to pressurize the fuel tank system during leak diagnostics.

The leak diagnostic unit consists of a plastic housing with

1. electrical air pump
2. a valve / solenoid which governs the air flow in the unit
3. a heater element (PTC resistor) which warms up the pump.

The electrical pump, valve and heater element in the unit are supplied with voltage by the system relay. The pump, valve and heater element are grounded (control) in the engine control module (ECM).

When leak diagnostics are not active, the valve is held open to ambient air for EVAP control to be carried out.

During leak diagnostics the pump in the leak diagnostic unit starts. The valve in the unit is operated by the engine control module (ECM) by grounding the different circuits internally in the engine control module (ECM).

The Engine control module (ECM) checks the fuel tanks system for leaks by pressurizing the system and at the same time monitoring a number of relevant parameters. Also see: LEAK DIAGNOSTICS (CERTAIN MARKETS ONLY)

The engine control module (ECM) can diagnose the leak diagnostic unit.

The valve in the leak diagnostic unit can be activated.

The leak diagnostic unit is at the upper front edge of the fuel tank.

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, use VIDA (Volvo 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-488592-S00159747132012072500000)
2. Original version for model year 2005-, see: «LEAK DIAGNOSTICS, ORIGINAL VERSION (2005-)»(ref-488592-S13782877322012072500000)
3. Improved version for all model years, see: «LEAK DIAGNOSTICS, IMPROVED VERSION (2004-)»(ref-488592-S25408987902012072500000)

See MISFIRE DIAGNOSTIC .

See CAMSHAFT DIAGNOSTICS (CVVT) .

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, use VIDA (Volvo 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. see «LEAK DIAGNOSTICS, ORIGINAL VERSION (2004)»(ref-488592-S00159747132012072500000)
2. see «LEAK DIAGNOSTICS, ORIGINAL VERSION (2005-)»(ref-488592-S13782877322012072500000)
3. see «LEAK DIAGNOSTICS, IMPROVED VERSION (2004-)»(ref-488592-S25408987902012072500000)

HEATED OXYGEN SENSOR (HO2S) DIAGNOSTICS

See HEATED OXYGEN SENSOR (HO2S) DIAGNOSTIC .

See THREE-WAY CATALYTIC CONVERTER (TWC) DIAGNOSTICS .

See FUEL PRESSURE REGULATION, DIAGNOSTICS .

Scheme 627

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) +4 °C or higher
6. Maximum altitude of 2500 meters above sea level.
7. Outside temperature between +4 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 while 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 diagnostic.

Scheme 628

Reference phase 1 (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.

Scheme 629

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.

LEAK DIAGNOSTICS, ORIGINAL VERSION (2004)

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 (fuel tank filler cap missing for example) 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. 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 +30 °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.

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 while 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 1
2. function test
3. leak diagnostic
4. reference phase 2.

Reference phase 1 (1-2)

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

Before the leak diagnostic begins, the control module runs reference phase 1 for leakage. During reference phase 1 (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 reference phase 1 (1-2), or if the value for pump power consumption 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. 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 reference phase 1, 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 every other 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). If the measured value reaches the calculated desired value within a certain time frame (determined by the fuel level in the tank), the engine control module (ECM) will continue to pressurize the fuel tank system so that the diagnostic for minor leaks (5-6) can be run.

However if the measured value does not reach the calculated desired value within a certain time (major leakage), the function of the leak diagnostic unit is checked again by running reference phase 2 (see " reference phase 2 " below). A diagnostic trouble code (DTC) for major leakage is stored, depending on the power consumption of the pump during reference phase 2.

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

The diagnostic for minor leaks is run every 14th time 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). If the measured value (6) is the same or less than the value stored in reference phase 1 (A) (minor leak) after a certain amount of time (the time is determined by the fuel level in the tank), reference phase 2 is run (see " reference phase 2 " below).

Scheme 630

Reference phase 2

The illustration shows the reference phase after the diagnostic for minor leaks, sealed fuel tank system.

Reference phase 2 is run when the power consumption of the pump is too low during the diagnostic for leakage. This is to ensure that lower power consumption (during the minor leak (6) diagnostic for example) is not caused by changes in components. If the measured power consumption during reference phase 2 (7) is lower than that measured during pressurization (6), the control module interprets this as meaning that the fuel tank system is sealed. A diagnostic trouble code (DTC) for minor leakage is stored if the measured power consumption from reference phase 2 (7) is the same or higher than that measured during pressurization (6).

The reference phase for major leaks is carried out in the same way.

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

The "operating cycle" for the diagnostic must have been run before the diagnostic can be completed. An operating cycle varies depending on the component or function being diagnosed. Certain diagnostics only require the ignition to be switched on and off for an operating cycle to be run. Other diagnostic require that several different conditions are met regarding for example

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

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

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

DIAGNOSTIC TROUBLE CODE (DTC) MEMORY

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

If the fault disappears, the diagnostic trouble code (DTC) will remain in the DTC memory for some time, but its status will change.

LEAK DIAGNOSTICS, IMPROVED VERSION (2004-)

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 (Volvo scan tool) 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 (Volvo scan tool), certain different conditions apply. See relevant information about these, available with starting Quick test fuel tank system in VIDA.

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.

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 air/fuel ratios poor ignition sparking insufficient compression.
2. normal variations caused by uneven combustion incorrect air/fuel ratios poor ignition sparking insufficient compression.
3. flywheel mechanical tolerances incorrect air/fuel ratios poor ignition sparking insufficient compression.
4. misfiring, which is caused by: incorrect air/fuel ratios poor ignition sparking 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 engine crankshaft rotations are divided into five intervals.

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 oscillations, caused by extremely 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 DSTC, traction control and/or ABS is active.

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 certain number of misfires during 1000 engine revolutions, this is interpreted as misfiring which affects emissions. 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 engine speed and load parameters within which the misfire was detected. For the diagnostic trouble code (DTC) to be stored, the misfire must occur twice more within the same engine speed and load parameters.

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 engine speed and load parameters must be met without misfiring before the engine control module (ECM) will begin counting down to extinguish the warning lamp and erase stored diagnostic trouble codes (DTCs) for misfiring.

In addition to electrical checks of the camshaft reset valve, the engine control module (ECM) checks that the position of the camshaft is correct and that the control (deployment and return of the camshaft) is working satisfactorily. The control module uses the signals from the camshaft position sensor and engine speed (RPM) sensor (crankshaft position) for the diagnostics.

Checking the camshaft position

The control module checks that the 0 position of the camshaft (mechanical rest position) is correct. During certain driving conditions, camshaft control is not active. If this is the case, the control module checks the deviation of the camshaft from the 0 position. This is the extent to which the camshaft flanks are deviating from predetermined positions on the crankshaft (reference positions).

The position of the camshaft is stored in the control module as an adaptation value. A diagnostic trouble code (DTC) is stored in the engine control module (ECM) if the adaptation value becomes too high or low. The deviation of the camshafts from the reference position can be read off using VIDA (Volvo scan tool).

Checking the camshaft control

When camshaft control is active, the control module checks that the camshaft moves to the intended position. This position ensures that the cam timing is correct so that the valves are opened and closed at the right time. This is done by measuring the time the system takes to deploy to the correct camshaft position (the transition time from the actual to the desired camshaft angle). A diagnostic trouble code (DTC) is stored in the engine control module (ECM) If the camshaft angle does not reach the desired value within a certain time frame. The function can be tested using VIDA (Volvo scan tool).

The front heated oxygen sensor (HO2S) is a linear type and functions with current control. Therefore it is 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 the diagnostic have been met.

The following faults can be registered by the control module

1. Electrical faults in circuits for the actual heated oxygen sensors (HO2S) and in their 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 fuel trim of the front and rear heated oxygen sensors (HO2S). The control module checks that the difference between the fuel trim in the front and rear heated oxygen sensors (HO2S) is not too great. The fault may be in the front or rear heated oxygen sensor (HO2S) or its wiring
4. Heated oxygen sensor (HO2S) dynamics. The control module checks that the switch time between rich and lean mixture is not too long
5. Implausible signals between the front and rear heated oxygen sensors (HO2S). When the control module registers a rich fuel air mixture at the front heated oxygen sensor (HO2S) and a lean mixture at the rear heated oxygen sensor (HO2S) or vice versa.

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 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 is upstream of the converter and one is 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 the efficiency of the catalytic converter is good and the fuel/air mixture is normal, the signal of the front heated oxygen sensor (HO2S) switches between rich and lean while the rear heated oxygen sensor (HO2S) is steady. If the efficiency of the three-way catalytic converter (TWC) is poor but the fuel/air mixture is normal, the signal from the rear heated oxygen sensor (HO2S) 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 heated oxygen sensor (HO2S) 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.

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

1. Fuel pump control module , a diagnostic checks the power supply. 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, a diagnostic checks the pressure and temperature signals 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 (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.

Components and 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.