Ignition and Control Systems - Design and Function (644 Body): Diagnosis Volvo S40 I рестайлинг

Diagnostic trouble codes (DTCs)

A diagnostic trouble code (DTC) is stored and the DSA warning lamp lights if the control module detects a fault. The exception is diagnostic trouble code (DTC) DSA-122 DSA warning lamp. This is because the DSA warning lamp cannot then be activated.

Faults, with the exception of diagnostic trouble code (DTC) DSA-122 DSA warning lamp, disengage the DSA function. If diagnostic trouble code (DTC) DSA-122 DSA warning lamp is stored, the warning lamp cannot be used to determine whether the DSA function is engaged or not. The DSA function is then always engaged cannot be disengaged manually.

If the DSA warning lamp is lit, the DSA function is not operating normally or it is not engaged.

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

Volvo on-board diagnostic (OBD) system

With VIDA it is possible to

1. Read off and erase stored diagnostic trouble codes (DTCs)
2. Reset adaptations
3. Activate components and functions according to certain predetermined patterns
4. Continuously monitor the value and status of the input and output signals for the system
5. Read off the control module identification.

To activate the Volvo on-board diagnostic (OBD) system for DSA

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. The on-board diagnostic (OBD) system can identify 17 different faults in the form of diagnostic trouble codes (DTCs).

Note. Diagnostic trouble codes (DTCs) DSA-112, DSA-223, DSA-224 and DSA-233 are only stored in the DSA control module while the ignition is on/the engine is running. When the ignition is switched off, these diagnostic trouble codes (DTCs) are erased. Therefore the engine must be started before diagnostic trouble codes (DTCs) are read off from the control module. This is so that the control module is able to re-check and store diagnostic trouble codes (DTCs).

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

Note. After the diagnostic trouble codes (DTCs) are erased the DSA function is disengaged. The DSA function is re-engaged using the DSA switch. If no diagnostic trouble codes (DTCs) have been stored, the DSA warning lamp goes out after engagement.

A diagnostic trouble code (DTC) is stored and the DSA warning lamp lights if the control module detects a fault. The exception is diagnostic trouble code (DTC) DSA-122 DSA warning lamp. This DSA warning lamp cannot be activated if this fault is stored.

Faults, with the exception of diagnostic trouble code (DTC) DSA-122 DSA warning lamp, disengage the DSA function. If diagnostic trouble code (DTC) DSA-122 DSA warning lamp is stored, the warning lamp cannot be used to determine whether the DSA function is engaged or not. The DSA function is then always engaged and cannot be disengaged manually.

If the DSA warning lamp is lit, the DSA function is not operating normally or it is not engaged.

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

Reading off the Volvo on-board diagnostic (OBD) system

See Reading off the Volvo on-board diagnostic (OBD) system

See Reading off the Volvo on-board diagnostic (OBD) system

See Reading off the Volvo on-board diagnostic (OBD) system

Scheme 68

Function in the dynamic stability assistance (DSA) anti-wheelspin system

the DSA system assists the driver in holding the vehicle under control under (hard) acceleration, especially when the road surface provides less grip than the driver anticipated.

It also makes progress possible in very slippery conditions, which would not otherwise be possible without dynamic stability assistance.

Unlike the SRS-, ABS- or SIPS-systems, the DSA system is not a safety system. It is an aid to improve control of the car.

The DSA system can be switched off, but is automatically engaged every time the ignition is switched on.

A warning lamp in the dashboard indicates the status of the DSA system.

The DSA system consists of a single control module. This control module calculates wheelspin in the driven wheels from the information about the speed provided by the ABS control module. From this information the DSA control module calculates the torque reduction that is required. This information is transferred to the engine control module (ECM) which decreases the torque on the driven wheels to the normal driving conditions.

The DSA control module does not have sensors of its own. It uses the ABS system or engine control module (ECM) sensors.

The DSA control module can be activated at all speeds, both when the car is moving forwards and when it is moving backwards.

There are no functional similarities between the DSA system and the TRACS system.

1. The TRACS system uses wheel braking to prevent wheelspin in one of the front wheels when the car moves off.
2. The DSA system decreases the engine torque to prevent wheelspin on one or both of the driven wheels in all driving conditions.

Scheme 69

The DSA system must take account of any deviations caused by the steering wheel. It is therefore important that no incorrect data is introduced by the system itself and that it goes through a number of stages before the torque reduction is activated.

1. When the DSA control module detects wheelspin it first determines the extent of the spin.
2. The average spin of the two front wheels is calculated. Differences in wheel speed because of cornering is compensated using sensors on the rear wheels.
3. Information about the engine speed and load comes from the engine control module (ECM). The torque required from the engine is calculated from this.
4. The selected gear can be derived by comparing wheel speed with engine speed. From this the friction coefficient between the tire and road surface can be deduced.
5. Acceptable spin can be deduced from the accelerator pedal (AP) position and the friction coefficient.
6. The engine control module (ECM) decreases torque by disengaging the injectors, so preventing wheel spin.

The DSA control module only sends information to the engine control module (ECM). It is this that close the fuel injection. The engine control module (ECM) can control the injection by closing the injectors, so that one or more injectors can be closed every 4th cylinder compression. It reduces torque in 16 stages.

1. Partial closure of the injectors occurs randomly to ensure that the heat is evenly distributed.
2. If the torque reduction is very small, a safety program is activated. After a given period the DSA shuts off several injectors (greater torque reduction) to ensure that the combustion chambers are correctly ventilated.
3. The DSA system functions up to maximum. It is also active while reversing.
4. The DSA system aligns itself so that it is does not identify different wheel diameter as wheelspin, in cases of variable tire pressure for example. DSA is not engaged if there is a slow puncture in one of the tires.
5. Switch off the DSA system when driving on a "special spare tire". If not the system aligns itself to the diameter of the tire on the wheel. To assist this the car should be driven slowly, then accelerated hard for approximately 4 seconds. The accelerator pedal (AP) should be released quickly so that the engine brakes the car for approximately 4 seconds. Repeat this one more time. This procedure should be repeated when the special spare tire is replaced by a normal tire.

Function test

The diagnostic is divided into different phases in which the components involved are tested before the actual leak diagnostic begins. The diagnostic is cancelled and a diagnostic trouble code (DTC) is stored if a fault is detected in any of the phases. The diagnostic test works as follows

1. The system must be depressurized. The control module checks that the pump diaphragm is in the resting position. Diagnostic trouble code (DTC) ECM-65, faulty signal, is stored if the control module registers that the position is active
2. When the engine is started, a vacuum is generated in the intake manifold. The three-way valve opens a connection to the intake manifold via the non-return valve. The diaphragm is moved to the activated position by the vacuum. Diagnostic trouble code (DTC) ECM-65, high signal, is stored if the control module registers that the diaphragm is still in the resting position
3. The three-way valve closes the connection with the intake manifold. The non-return valve closes. A connection to the atmospheric pressure opens. The spring-loaded diaphragm must then return to resting position. Diagnostic trouble code (DTC) ECM 65, low signal, is stored if the diaphragm does not return to the resting position.

Scheme 70

1. The leak diagnostic pump is pulsed (A) rapidly at a rapid frequency. This is to pressurize the fuel tank system to the desired pressure (C)
2. This rapid pulsing is interrupted regularly (B). This is to check that the correct pressure in the fuel tank system is reached. This is done by gauging the time taken for the pump to switch from active to resting position using the switch in the leak diagnostic pump. The constant pulse (A) and pressure check (B) alternate until the desired pressure (C) in the fuel tank system is obtained. If vehicle speed exceeds 40 km/h, there is no pressure check (B). The pump is activated and deactivated a fixed number of times instead. If the pressure (C) is not reached, the control module interprets it as a leakage. Diagnostic trouble code (DTC) ECM-6A, fuel tank filler cap missing, is stored
3. When the pressure in the fuel tank is detected by the control module using the leak diagnostic pump, the control module begins to check for smaller leaks (D). To do this, the control module measures the time the diaphragm takes from active to resting position. Diagnostic trouble code (DTC) ECM-68, large leak, or ECM-68, small leak, is stored if this time is too short
4. If no leakage is detected in the fuel tank system, the flow in the evaporative emission (EVAP) system is checked for blockage. This is done by pulsing both the canister purge (CP) valve and the leak diagnostic pump at the same time. The control module checks that the pressure in the fuel tank drops (E). If the pressure does not drop, the control module interprets it as a blockage in the evaporative emission (EVAP) system. Diagnostic trouble code (DTC) ECM-6A is stored. The canister purge (CP) valve is pulsed until the fuel tank system is depressurized. The diagnostic takes place in the next operating cycle.

On Board Diagnostics II (OBD II)

Only USA/CDN

See On Board Diagnostics II (OBD II)