Electronics - Design and Function - 3 of 4: Diagnosis Volvo C70 II

CAMSHAFT DIAGNOSTICS (CVVT)

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).

HEATED OXYGEN SENSOR (HO2S) DIAGNOSTIC

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.

MISFIRE DIAGNOSTIC

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.

Scheme 827

The engine control module (ECM) controls the following functions

1. start
2. injectors
3. ignition
4. fuel pressure
5. turbocharger (TC) control
6. throttle
7. camshafts (CVVT)
8. evaporative emission system (EVAP) valve
9. engine cooling fan (FC)
10. Air conditioning (A/C) compressor
11. alternator control module (ACM) (2005-).

The engine control module (ECM) is supplied with battery voltage via fuses in the central electronic module (CEM) and in the integrated relay/fusebox in the engine compartment.

To prevent certain stored date from being erased from the engine control module (ECM) when the ignition is switched off, the control module also has a 30-supply. This supply is from the integrated relay/fusebox in the engine compartment.

The control module is grounded via the wiring which is connected at the right-hand suspension turret.

The engine control module (ECM) contains a voltage regulator which maintains a low voltage (5 V) in internal components in the control module such as

1. Analog/Digital converter
2. Digital/Analog converter
3. Micro-processor.

The functions which require battery power and high output are controlled by external or internal power stages. For example ignition coils have external power stages (integrated into the ignition coils) while the power stages for the injectors are integrated into the control module.

The micro-processor in the engine control module (ECM) receives signals from the different sensors and control modules in the vehicle. The micro-processor uses a program which calculates how the signals from the different sensors and other control modules are to be interpreted and how the components / functions need to be controlled.

The control module has several self-learning (adaptive) functions. It continually adapts ongoing calculations to changing circumstances (wear, air leaks, differences between different fuels).

Emissions are kept low through efficient management of the injection period, ignition, evaporative emission system (EVAP) valve and camshafts etc. Faults which affect emissions can be detected by running diagnostics for functions and components.

The engine control module (ECM) is in the intake system. It is cooled by the engine intake air.

The engine control module (ECM) communicates with other control modules using controller area network (CAN) communication.

The engine control module (ECM) checks activations, input and output signals and functions using an integrated diagnostic system. A diagnostic trouble code (DTC) is stored if, after validation, the control module detects a fault. In certain cases the faulty signal is also replaced with a substitute value or certain functions are limited.

For example, substitute values can be set for

1. engine coolant temperature (ECT) sensor
2. mass air flow (MAF) sensor
3. throttle position (TP) sensor
4. air pressure
5. fuel pressure.

Mathematical calculations and signals from certain components are used to calculate the substitute values. Other substitute values are fixed, predefined values in the control module.

The substitute value allows the car to be driven and for the emissions to be kept at a reasonable level even though vital functions/components are malfunctioning.

Functions which may be limited are for example

1. turbocharger (TC) control
2. Camshaft control (CVVT)
3. fuel trim
4. throttle angle.

The substitute values are used and functions restricted so that the system is still able to work while protecting components that are required for safety reasons (for example the throttle angle).

Any diagnostic trouble codes (DTCs) are stored in the control module memory. This information can be read off using VIDA via the data link connector (DLC) in the vehicle.

DIAGNOSTIC FUNCTIONS

see DIAGNOSTIC FUNCTIONS

All diagnostic communication regarding the gas discharge lamp module (GDL) is handled via the central electronic module (CEM).

DIAGNOSTIC TROUBLE CODES (DTCS)

If the central electronic module (CEM) detects a fault in the headlight system, it stores a diagnostic trouble code.

A fault detected during the last driving cycle is defined as permanent. Other faults that are detected are defined as intermittent.

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.

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.

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

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. A fault which is detected in the most recent operating cycle is defined as permanent. Other faults are defined as intermittent. An operating cycle involves ignition on, the vehicle speed exceeding 20 km/h and the ignition being switched off.

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 master unit for the immobilizer system is the central electronic module (CEM). This is also the module which stores diagnostic trouble codes (DTC) for faults in the immobilizer system.

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. This control module can store up to six diagnostic trouble codes (DTCs), the three first and the three latest.

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. The on-board diagnostic (OBD) system can identify 35 different faults in the infotainment control module (ICM). These are stored as diagnostic trouble codes (DTCs). This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

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

ON-BOARD DIAGNOSTIC SYSTEM (OBD SYSTEM)

Indicates the status of the most recent diagnostic.

1. OK = There are no faults in the MOST network
2. Poor = The infotainment control module (ICM) receives a signal on the MOST network but cannot decode it
3. Pos 0 - 8 = An open-circuit has been detected in the specified position in the network.

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. This control module can store up to 6 diagnostic trouble codes (DTCs), the three first and the three latest.

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. The on-board diagnostic (OBD) system can identify 33 different faults in the infotainment control module (ICM). These are stored as diagnostic trouble codes (DTCs). This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

Diagnostic trouble codes can only be erased once all the diagnostic trouble codes have been read out 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. This control module can store up to 6 diagnostic trouble codes (DTCs), the three first and the three latest.

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. The on-board diagnostic (OBD) system can identify 33 different faults in the infotainment control module (ICM). These are stored as diagnostic trouble codes (DTCs). This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

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. This control module can store up to 6 diagnostic trouble codes (DTCs), the three first and the three latest.

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. The on-board diagnostic (OBD) system can identify 36 different faults in the infotainment control module (ICM). These are stored as diagnostic trouble codes (DTCs). This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

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.

If the control module detects a fault, a diagnostic trouble code is generated. The control module can store up to 10 trouble codes. A fault that is detected during the most recent operating cycle is defined as permanent. Other faults that are detected are defined as intermittent.

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.

If the control module detects a fault, a diagnostic trouble code is generated. The control module can store up to 10 trouble codes. A fault that is detected during the most recent operating cycle is defined as permanent. Other faults that are detected are defined as intermittent.

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.

If the control module detects a fault, a diagnostic trouble code is generated. The control module can store up to 10 trouble codes. A fault that is detected during the most recent operating cycle is defined as permanent. Other faults that are detected are defined as intermittent.

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.

If the control module detects a fault, a diagnostic trouble code is generated. The control module can store up to 10 trouble codes. A fault that is detected during the most recent operating cycle is defined as permanent. Other faults that are detected are defined as intermittent.

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 keyless vehicle module (KVM) has internal diagnostics. It continuously monitors most of the inputs and outputs. It does not monitor the outputs for the antennas. The antennas are checked every 5th operating cycle when vehicle speed exceeds 20 km/h (11 mph).

A diagnostic trouble code (DTC) is stored if the keyless vehicle module (KVM) detects a fault. The keyless vehicle module (KVM) can identify 42 different faults. If for any reason a fault should disappear after the diagnostic trouble code (DTC) has been stored, information about the diagnostic trouble code (DTC) remains in the keyless vehicle module (KVM).

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function. The on-board diagnostic (OBD) system can identify 42 different faults in the keyless vehicle module (KVM). These are stored as diagnostic trouble codes (DTCs).

This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

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

The keyless vehicle module (KVM) has internal diagnostics. It continuously monitors most of the inputs and outputs. It does not monitor the outputs for the antennas. The antennas are checked every 5th operating cycle when vehicle speed exceeds 20 km/h (11 mph).

A diagnostic trouble code is generated if Keyless vehicle module (KVM) detects a malfunction.

Keyless vehicle module (KVM) can identify 34 different malfunctions. Should a problem disappear for some reason after the diagnostic trouble code was generated, information about the diagnostic trouble code remains in the memory of Keyless vehicle module (KVM).

Stored diagnostic trouble codes (DTCs) can be read off and erased using this function. The on-board diagnostic system can identify 34 different faults in the keyless vehicle module (KVM). These are stored as diagnostic trouble codes (DTCs).

This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

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

RING BREAK DIAGNOSTICS

General

This function is important when fault-tracing the MOST network. Ring break diagnostics are used when there is an open-circuit in the MOST network and diagnostic trouble code (DTC) ICM-DC02 has been stored in the infotainment control module (ICM).

A ring break diagnosis means that all control modules send a message to the infotainment control module (ICM) in reverse order to their locations in the MOST network. This means that the integrated audio module (IAM) transmits first, not last. The control module which does not work will not transmit a response to the infotainment control module (ICM). This also means that all control modules connected before the broken control module will not be able to transmit a message to the infotainment control module (ICM).

The same applies in the event of an open-circuit in the fiber optic cable in the MOST network. None of the control modules before the open-circuit will be able to send their message to the infotainment control module (ICM). The infotainment control module (ICM) is then able to calculate the position of the open-circuit from the incoming messages.

HINT: It is important to know which control modules are connected and in what order to identify the control module which sends each message.

Scheme 828

Example 1

A MOST network contains all 8 control modules. There is an open-circuit in the cable between the traffic message channel module (TMC) and the Subwoofer module (SUB). See the illustration.

During the ring break diagnostic, the infotainment control module (ICM) receives responses in reverse order to the order of the control modules on the MOST network. Those that are before the Traffic message channel module (TMC) cannot respond to the infotainment control module (ICM). The infotainment control module (ICM) receives responses up to position four and presents the value 4.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK".

Example 2

A MOST network to which the Phone module (PHM) is not connected, however the other seven control modules are connected.

There is an open-circuit in the cable between the traffic message channel module (TMC) and the audio module (AUD).

During the ring break diagnostic, the response value from all the control modules before the Phone module (PHM) will be 1 less than when all control modules are connected. The infotainment control module (ICM) receives responses up to position three and presents the value 3.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK".

This function is important when fault-tracing the MOST network. Ring break diagnostics are used when there is an open-circuit in the MOST network and diagnostic trouble code (DTC) ICM-DC02 has been stored in the infotainment control module (ICM).

During a ring break diagnostic, all control modules transmit a message to the infotainment control module (ICM) in reverse order to their position on the MOST network. This means that the Integrated Audio Module (IAM) transmits first, not last.

The control module which is not working will not transmit a response to the infotainment control module (ICM). This also means that the control modules which are connected before the defective control module will be unable to transmit a message to the infotainment control module (ICM).

The same applies in the event of an open-circuit in the fiber optic cable in the MOST network. None of the control modules before the open-circuit will be able to send their message to the infotainment control module (ICM). The infotainment control module (ICM) is then able to calculate the position of the open-circuit from the incoming messages.

HINT: It is important to know which control modules are connected and in what order to identify the control module which sends each message.

Scheme 829

Example 1

A MOST network contains all 8 control modules. There is an open-circuit in the cable between the Remote Digital Audio Receiver (RDAR) and the Audio module (AUD). See the illustration

During the ring break diagnostic, the infotainment control module (ICM) receives responses in reverse order to the order of the control modules on the MOST network.

Those that are before the audio module (AUD) cannot respond to the infotainment control module (ICM). The infotainment control module (ICM) receives responses up to position five and presents the value 5.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK".

Example 2

A MOST network to which the subwoofer module (SUB) is not connected, however the other eight control modules are connected.

There is an open-circuit in the cable between the Remote Digital Audio Receiver (RDAR) and the audio module (AUD).

During the ring break diagnostic, the response value from all the control modules before the subwoofer module (SUB) will be one less than example 1 when all control modules are connected. The infotainment control module (ICM) receives responses up to position four and presents the value 4.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK".

This function is important when fault-tracing the MOST network. Ring break diagnostics are used when there is an open-circuit in the MOST network and diagnostic trouble code (DTC) ICM-DC02 has been stored in the infotainment control module (ICM).

During a ring break diagnostic, all control modules transmit a message to the infotainment control module (ICM) in reverse order to their position on the MOST network. This means that the Integrated Audio Module (IAM) transmits first, not last.

The control module which is not working will not transmit a response to the infotainment control module (ICM). This also means that the control modules which are connected before the defective control module will be unable to transmit a message to the infotainment control module (ICM).

The same applies in the event of an open-circuit in the fiber optic cable in the MOST network. None of the control modules before the open-circuit will be able to send their message to the infotainment control module (ICM). The infotainment control module (ICM) is then able to calculate the position of the open-circuit from the incoming messages.

HINT: It is important to know which control modules are connected and in what order to identify the control module which sends each message.

Scheme 830

Example 1

A MOST network contains all 8 control modules. There is an open-circuit in the cable between the Remote Digital Audio Receiver (RDAR) and the Audio module (AUD). See the illustration (applies to the S40/V50).

During the ring break diagnostic, the infotainment control module (ICM) receives responses in reverse order to the order of the control modules on the MOST network.

Those that are before the audio module (AUD) cannot respond to the infotainment control module (ICM). The infotainment control module (ICM) receives responses up to position five and presents the value 5.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK".

Example 2

A MOST network to which the subwoofer module (SUB) is not connected, however, the other seven control modules are connected.

There is an open-circuit in the cable between the Remote Digital Audio Receiver (RDAR) and the audio module (AUD).

During the ring break diagnostic, the response value from all the control modules before the subwoofer module (SUB) will be one less than example 1 when all control modules are connected. The infotainment control module (ICM) receives responses up to position four and presents the value 4.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK".

General

This function is important when fault-tracing the MOST network. Ring break diagnostics are used when there is an open-circuit in the MOST network and diagnostic trouble code (DTC) ICM-DC02 has been stored in the infotainment control module (ICM).

During ring break diagnostics, all control modules transmit a message to the infotainment control module (ICM) in reverse order to their position on the MOST network. This means that the Accessory USB unit (AUU) transmits first, not last.

The control module which is not working will not transmit a response to the infotainment control module (ICM). This also means that the control modules which are connected before the defective control module will be unable to transmit a message to the infotainment control module (ICM).

The same applies with an open circuit on the optical cable in the MOST network. No control module before the open circuit can send messages to the Infotainment control module (ICM).

By means of the incoming messages, the Infotainment control module (ICM) can determine where the open circuit has taken place.

HINT: It is important to know which control modules are connected and in what order to identify the control module which sends each message.

Scheme 831

Example 1

A MOST network contains all 7 control modules. There is an open-circuit in the cable between the Remote Digital Audio Receiver (RDAR) and the Audio module (AUD). See the illustration (applies to the S40/V50).

During the ring break diagnostic, the infotainment control module (ICM) receives responses in reverse order to the order of the control modules on the MOST network.

Those that are before the audio module (AUD) cannot respond to the infotainment control module (ICM). The infotainment control module (ICM) receives responses up to position four and presents the value 4.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK.

Example 2

A MOST network to which the Phone module (PHM) is not connected, however the other six control modules are connected.

There is an open-circuit in the cable between the Remote Digital Audio Receiver (RDAR) and the audio module (AUD).

Using ring break diagnostics, all control modules before the Phone module (PHM) will have minus one on its response compared to example 1 where all control modules were connected.

Infotainment control module (ICM) receives responses up to position three and presents the value 3.

If there was no open-circuit, the infotainment control module (ICM) would have responded "OK.

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. 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.

If a fault is no longer permanent, the diagnostic trouble code (DTC) remains as intermittent.

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.

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

If the control module detect a fault, a diagnostic trouble code is stored. A fault that was detected during the last driving cycle is defined as permanent. Other faults that are detected are defined as intermittent.

Should a fault disappear for any reason after being stored in the control module as a permanent diagnostic trouble code, the information remains stored in the control module. If a fault is no longer permanent, the diagnostic trouble code remains as intermittent.

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 not available until the diagnostic trouble codes have been erased.

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

If the control module detects a fault, a diagnostic trouble code is stored. A fault that was detected during the last driving cycle is defined as permanent. Other faults that are detected are defined as intermittent.

Should a fault disappear for any reason after being stored in the control module as a permanent diagnostic trouble code, the information remains stored in the control module. If a fault is no longer permanent, the diagnostic trouble code remains as intermittent.

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.

A diagnostic trouble code (DTC) is stored if the control module detects a fault. The control module can store a number of diagnostic trouble codes (DTCs).

If a fault disappears for any reason after the diagnostic trouble code (DTC) has been stored in the control module, information about the fault remains in the control module. If a fault is no longer permanent the diagnostic trouble code (DTC) remains as intermittent.

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

This function can also be used to read off whether the fault is still present (permanent) or whether it has now ceased (intermittent) after the diagnostic trouble code (DTC) has been stored.

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. There are approximately 18 diagnostic trouble codes (DTCs) for standard carphones, approximately 25 for carphones with Volvo On Call. A fault which is detected in the most recent operating cycle is defined as permanent. Other faults which are detected are defined as intermittent.

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.

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

If the control module detects a fault, a diagnostic trouble code is stored. A fault that was detected during the last driving cycle is defined as permanent. Other faults that are detected are defined as intermittent.

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.

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.