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Glossary of terms you will come across during your Phase 2 training.

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This identifier indicates the type of failure that is associated with the component. The FMI has been adopted from the SAE practice of J1587 diagnostics. The FMI follows the parameter identifier (PID) in the descriptions of the fault code. The descriptions of the FMIs are in the following list:

0 - The data is valid but the data is above the normal operational range.

1 - The data is valid, but the data is below the normal operational range.

2 - The data is erratic, intermittent or incorrect.

3 - The voltage is above normal or the voltage is shorted high.

4 - The voltage is below normal or the voltage is shorted low.

5 - The current is below normal or circuit is open.

6 - The current is above normal or the circuit is grounded.

7 - The mechanical system is not responding properly.

8 - There is an abnormal frequency, an abnormal pulse width, or an abnormal time period.

9 - There has been an abnormal update.

10 - There is an abnormal rate of charge.

11 - The failure mode is not identifiable.

12 - The device or the component is damaged.

For example, in the diagnostic code: 110 - 3, the 110 is the CID, in this case, the coolant temperature sensor. The 3 is the Failure Mode Identifier (FMI), in this case, voltage high.


Foras Áiseanna Saothair: Irish for Training and Employment Authority.

FÁS is Ireland's National Training and Employment Authority.

FÁS Training Centre, Cabra.


Feeler bladesMeasuring blades used by cp fitters to accurately measure small distances between components. For example, feeler blades are used when setting valve clearances in an engine:

Setting valve clearance using feeler blades

A metal containing iron. Examples are pig iron, wrought iron, cast iron and steel.

Field coils are used in motors. They are called field coils because they consist of a soft iron core, around which is wrapped coils of wire (coils). When electricity is passed through these coils of wire, a magnetic field is produced (field) - hence the term 'field coils'.

Starter motor field coils.


Alternator rotor.

In the context of alternators, field excitation is the act of passing electrical current through the windings on the rotor. The more current we pass through these windings, the stronger the magnet we produce, and the more electricity we generate. In order to regulate the voltage, we switch on and off this field circuit with a voltage regulator.


Often (incorrectly) referred to as the "diff", the final drive is where drive coming down the propeller shaft is:

  • Reduced in speed and increased in torque by means of having a small pinion drive a large crownwheel.
  • The drive is turned through 900 in order to reach the driving wheels via the halfshafts.

Final drive and halfshaft.

These are the two functions of the final drive. This unit usually has the differential gears mounted on it. The funcion of the differential is to allow the driving wheels to turn at different speed but always equal torque.


Final Drive Differential Unit

Correct name of the unit of a live (driving) axle on a vehicle. The unit is sometimes referred to as the "diff", "differential" or the "final drive", when, in actual fact the unit is a combination of both these components.

There is a crown wheel and pinion which is the final drive. The functions of this unit are:

  • To carry out the final speed reduction and torque increase of the power going to the road wheels.
  • To turn drive through 900, from the propeller shaft to the half shafts.

There is also a cluster of gears known as the differential. The function of the differential is to allow the driving wheels to turn at different speeds, but always equal torque.

The Fire Point of a liquid is the temperature at which sufficient vapour is given off to cause the fire to burn continually if a heat source is present.

Firewire is a way of very rapidly transferring data to and from a computer. Modern computers have firewire ports, and you can use them to connect devices such as digital video cameras to your machine.

Firewire connection at the back of the computer.

Symbol for Firewire:

Firewire symbol

Firewire ports are very similar to USB ports in appearance, but cables and ports are incompatible. If you don't have firewire, it is possible to buy an add in card with the ports. You can do this for both desktop and laptop (notebook) computers.

Firewire card:

Firewire card.

IEEE 1394, Firewire, ilink and lynx are all manufacturers' names for cables that meet the IEEE 1394 standard for data transfer. This standard supports data transfer speeds of up to 400 Mbps (400 million bits per second).

Check Wikipedia for more information.


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