RA. General

RA. General

Note: Use only the memory cassette indicated in the section Special tools. The messages contained in older versions of the cassette may have different meanings to those in this manual.

Applications

Faults are registered and stored in Running Test. Because the Volvo ST stores short term as well as long term faults the Volvo ST is suitable for intermittent faults.




Test description

The ST tests signals in sequence and then starts from the beginning again. Certain tests are carried out in parallel while others require that the microcomputer works on one test at a time.

In certain cases different fault messages can be given for the same fault. This is because the secondary fault is only detected by the ST before the faulty signal is measured.

An example is a break in the RPM sensor signal which can give several different fault messages depending on the point at which the fault is detected in the test.




In several tests the ST needs to measure another value to ascertain whether a fault has occurred or if the value is normal. This means that a test can take so long that the ST cannot perform the entire test before engine speed has decreased to its lower limit.

An example is the power supply from the ignition switch. if the power supply is lost to MFI#35, DI#6 or power stage #4 the other units are tested before a fault message is logged. If all three units are without power the ST assumes that the Ignition switch is in position 0.




Priority

A fault can generate secondary faults. The ST will display the primary fault first, followed by the others in order of priority.

Because the secondary faults have been generated by the primary fault only the primary fault is remedied. This does not apply If It is suspected that there are several independent faults in the system. The secondary fault will disappear when the primary fault has been remedied.

Primary faults not generating secondary ones will be displayed in the order In which they are detected.

Order of priority
1. Power supplies to the control module.
2. Control module connections to GND.
3. Sensor signals which affect the basic functions of the engine, engine speed signal for example.
4. Other signals, the idle switch for example.




Lower engine speed limit

When the RPM sensor signal corresponds to a low engine speed, the control modules do not transmit any ignition pulses, injector pulses, relay control signals etc and the engine stops.

The engine speed limit can vary depending on the setting of and wear on the RPM sensor and drive plate/flywheel.

The ST cannot tell if the signals disappear because of a fault or because the engine has stopped for some other reason. The ST will display End of test, No faults found.

Faults with lower priorities than the engine speed signal will not be saved. However faults with higher priorities, such as power supplies, will be stored it they are the cause of the engine stopping running.