Engine Management Systems - Design and Function: Diagnosis Volvo S80 I рестайлинг

Diagnostic functions

See Diagnostic functions

See Diagnostic functions

Camshaft diagnostics

The task of the variable camshaft is to alter the camshaft position to minimize emissions and optimize the engine performance. The camshaft displacement in relation to the crankshaft is calculated using the engine load and engine speed (RPM).

The diagnostic consists of 4 parts

1. When the ignition is switched on, an electrical check is carried out on the signal cable, the power supply cable and the solenoid. The check is for a short-circuit to supply voltage / ground and open-circuit. This diagnostic is switched off when the engine is running
2. When the camshaft is in its 0 position (mechanical resting position), it is checked to see if it is in the correct position compared to the flywheel. If the deviation is excessive the variable camshaft is switched off
3. In case of larger controlled deviations at the variable camshaft the time taken to regulate to the control value is measured. This time is used partially to determine how long it takes to alter the camshaft angle and partially to switch off the variable camshaft if the time exceeds a certain maximum time. The information about the speed at which the camshaft angle changes is used in the control strategy. The camshaft uses the engine oil and oil pressure to turn. The turning time depends on oil pressure, viscosity etc. which in turn depends on oil temperature and quality etc.
4. The camshaft position (CMP) sensor is compared with the flywheel sensor to check if the camshaft position (CMP) sensor detects all lobes.

The mechanical 0 position depends on the engine type

For turbocharged engines the camshaft mechanical 0 position is in the performance position.

For 6 cylinder naturally aspirated engines the camshaft mechanical 0 position is the low speed position.

For 5 cylinder naturally aspirated engines the camshaft mechanical 0 position is the low speed position.

Misfire diagnostic

If the fuel / air mixture does not ignite in the ignition stroke the engine is misfiring. The engine control module (ECM) detects misfires by registering the time between two segments of the flywheel.

The time between the two segments varies depending on

1. misfiring
2. driveline oscillations
3. normal variations caused by uneven combustion
4. flywheel mechanical tolerances.

The mechanical tolerances and drive line oscillations disrupt the signal and it is difficult to detect whether the engine is misfiring or not. An adaptation of the flywheel signal is being made in order to eliminate the mechanical fault in the flywheel. Two camshaft revolutions are divided into five intervals for 5 cylinder engines and six intervals for 6 cylinder engines. The aim of this modification is to filter out the normal distortion present in the flywheel. By registering the time difference between the intervals and comparing this with the normal distortion in the flywheel, misfires can be gauged. In order for the engine control module (ECM) to register misfires, the flywheel must be adapted. Misfire diagnostics are shut off until the flywheel is adapted for the first time. This value is saved and then used in subsequent operating cycles.

Adaptation of the flywheel is done when

1. the engine speed (RPM) is between 2300 RPM and 3000 RPM
2. the load should exceed 40 % of relative load (RL), which corresponds to normal forward travel on a smooth road at approximately 100 km/h.

Flywheel adaptation takes approximately 60 seconds.

Drive line oscillations, caused by uneven road surfaces for example, may lead to uneven engine operation. Drive line oscillations will be registered by the ABS system and the information sent to the engine control module (ECM). The engine control module (ECM) uses this information to differentiate between these oscillations and real misfiring. Misfire diagnostics are shut off in the event of drive line oscillations

Misfire diagnostics are also shut off when

1. leak diagnostic, when leak diagnostics are taking place
2. diagnostic trouble codes (DTCs) in the flywheel sensor, mass air flow (MAF) sensor, engine coolant temperature (ECT) sensor and leak diagnostic.

Misfiring lights the malfunction indicator lamp (MIL). In the event of misfiring, if there is risk of damage to the three way catalytic converter, the malfunction indicator lamp (MIL) will flash and then switch to a constant light.

The engine control module (ECM) registers and stores the RPM and load ranges within which the misfire occurred. For the diagnostic trouble code (DTC) to be stored, the misfire must occur a further two times within the same RPM and load ranges. The malfunction indicator lamp (MIL) lights if the diagnostic trouble code (DTC) for misfire is stored in the previous operating cycle and a new diagnostic trouble code (DTC) for misfire is received in the next operating cycle.

If the misfire stops, the requirements for the RPM and load ranges must be met without any misfires before the engine control module (ECM) will begin counting down to extinguish the warning lamp and erase stored diagnostic trouble codes (DTCs) for misfiring.

Four different conditions for diagnostics

Trip

When all diagnostic functions have been gone through.

Drive cycle

Begins 15 seconds after the engine starts and finishes when the engine is switched off.

Warm-up cycle

Begins when the engine starts and engine coolant temperature (ECT) is below 40 °C (104 °F) and finishes when the engine temperature is above 84 °C (183.2 °F).

Time

Some diagnostics are carried out a set amount of time after a particular occurrence (for example when vehicle speed is above 23 km/h (14.3 mph)).

Emissions related diagnostic functions

The engine control module (ECM) checks that the emissions related functions are working. These systems are checked by an ongoing diagnostic function. The diagnostic function checks that the relevant components and the actual function in the system are working. It is called a trip when all diagnostic functions have been gone through. Trip time may vary depending on driving style, but normally it takes approximately 25 minutes fir mixed driving.

Diagnostic trouble code (DTC) memory

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

If the fault disappears, the diagnostic trouble code (DTC) will be present for a longer time in the diagnostic trouble code (DTC) memory although the status of the code will have changed.

Throttle diagnostic

For more information about the electronic throttle unit system and related components such as the throttle unit, accelerator pedal sensor, stop lamp switch, clutch pedal sensor switch and brake pedal position sensor, see Design and Function .

See Camshaft diagnostics

See Misfire diagnostic

Probe diagnostics

See Probe diagnostics

Three-way catalytic converter (TWC) diagnostics

See Three-way catalytic converter (TWC) diagnostics

See Throttle diagnostic

See Camshaft diagnostics

See Misfire diagnostic

See Probe diagnostics

See Three-way catalytic converter (TWC) diagnostics

See Throttle diagnostic

Scheme 142

Leak diagnostic

The diagnostic has the same version and function as the ME 7.0 on the S70, V70 and C70.

The diagnostic has the same version and function as the ME 7.0 on the S70, V70 and C70.

Diagnostics, fault-tracing

See Diagnostics, fault-tracing

See Diagnostics, fault-tracing