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

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K-line, L-line

The K-Line is a very low-speed single-wire serial communication system used on many motor vehicles and commercial vehicles. It is commonly used for the diagnostic connections between the Electronic Control Modules (ECMs) on the vehicle and the diagnostic equipment (scan tools and data loggers). The K-Line is a network based upon the ISO9141 specifications, also known as the 9141 California Air Resources Board (CARB) Standard.

The K-Line is very different to a CAN Bus network and from most communication networks in general. A CAN Bus network, for example, does not have either a central or a primary ECM: all the ECMs are equal as they are all able to transmit messages along the network as well as receive messages.

On the K-Line network or any network compliant with ISO 9141, the direction of message flow is extremely important. The control of the network is dominated by the master ECM, and the message direction and timing depend on which ECM is talking (sending a message) and which ECMs are listening (waiting for a message). Two ECMs therefore cannot send a message at the same time, but have to wait in turn until allowed by the Master ECM.

There is only one wire for all communication on the network. The messages therefore need to be sent in binary format and transmitted as a pulsed voltage signal. The voltages on the K-Line are pulsed between two values in binary code (a series of ones and zeroes).

Note 1: A K-Line message is different to a CAN message, as CAN always sends an entire message at once while K-Line may send messages split into several parts.

Note 2: A CAN Bus network operates constantly as a communication network and a diagnostic network between the ECMs whilst the vehicle is in operation. The K-Line network is only intended to support diagnostic equipment. However, when a diagnostic machine is not present, the K-Line wiring may be used by other ECMs for communication at different baud rates and with different timing patterns.

The K-Line is a bi-directional one-wire-bus interface for data transfer within the automotive environment compliant with ISO 9141 and ISO 14230-1.

K- Line and L-Line are utilised predominately for external communication (with diagnostic equipment), typically to provide on-board diagnostic of ECUs in the garage.

Read more here about using a picoscope to test these lines.


Kawasaki GeneratorGE 4300 A 110V/220V electrical generator, used on the small plant course.


The kelvin is a unit of measure for temperature and is one of the seven base units in the International System of Units (SI). It is  and is assigned the unit symbol K.

The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all thermal motion ceases in the atoms of the substance whose temperature we are measuring. 

Water reaches absolute zero at -273.16oC (0 kelvin)

Water boils at 373.16k (100oC, at sea level)


Company contact for Whelan Plant Sales.


  • Landline: 065 840488


  • Ciaran Lynch, 2g1cp13b

Charles Franklin KetteringThis system is an ignition system named after its inventor, Charles Franklin Kettering. You can read more about Kettering on Wikipedia.

This system describes the basic principle behind all battery powered automotive ignition systems.

The system uses 2 sets of windings:

  1. Primary windings, capable of carrying a relatively large current (3-4 amperes in the original systems which were controlled (switched) by contact breaker points).
  2. Secondary windings, much finer, and generally with about 150 times as many turns as the primary windings. They did not have to be able to carry large amounts of current, but because of the turns ratio between the primary and secondary windings, a very high voltage was generated in the secondary windings everytime the primary windings were switched off.

The Kettering system

The turns ratio alone did not provide the huge step-up in voltage between the primary circuit voltage of 12V and the secondary output of 10-15kV.

When the primary winding was switched off, the magnetic field around it collapsed, inducing current in the secondary winding.

However, the primary winding also collapsed across itself, also inducing a voltage in the region of 300-400V.

Also, because of the auto-transformer connection, once the points open, the primary and secondary windings are effectively wired in series with each other - both the primary and secondary windings produce the HT voltage necessary for electrons to jump across a spark gap.

The auto-transformer connection is where the primary windings are joined to the secondary windings. See the video at 4 mins, 10 sec for further explanation of this connection.

When the points are closed, electricity will flow through the primary windings, through the contact breakers and then to ground.

When the points are opened, the primary and secondary windings are effectively wired in series, and, together, they produce the high voltage required for a spark.

It was this higher voltage, and the turns ratio between the primary and secondary windings that enabled the system to produce the high voltage necessary to produce a spark inside the dense, highly compressed atmosphere of the combustion chamber.


Your Phase 2 course content is laid out in 6 technical modules. Each module is further sub-divided into learning units.

Each learning unit sets out the desired learning outcomes, the key learning points, the resources required and suggested exercises.

The key learning points are the points and topics to be covered by your instructor to help you attain the learning outcomes.


This means switching on the ignition.

In the context of electronic engine management, 'key-on' describes the event of switching on the ignition.


Keyword Protocol 2000, sometimes abbreviated KWP2000, is a communications protocol used for on-board vehicle diagnostics systems (OBD). The protocol is standardized by International Organization for Standardization as ISO 14230.

The physical layer is identical to ISO 9141-2, with bidirectional serial communication on a single line called the K-line. In addition, there is an optional L-line for wakeup. The data rate is between 1.2 and 10.4 kilobaud, and a message may contain up to 255 bytes in the data field.


Prefix for units of measurement: for example kilometre - a thousand metres; kilogramme - a thousand grammes.

Check here for more on prefixes and units of measurement.

Prefixes for units of measurement


1 kilobyte = 1024 bytes. Don't get confused here! The prefix kilo normally means one thousand, but when we are dealing with bits and bytes, we are dealing with binary numbers, and in this case 210, which is:


This type of stuff is covered during your electronics training.

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Please note, if you want to contact the main Training Centre in Baldoyle, you need to ring 01-8167400.

If you want to contact the CP Fitters' Section, you can Contact Us by email,, or by telephone: 00 353 1 8167543 This number gets you through to the CP Fitters' Section, Baldoyle Satellite Unit.

Our Address is : Construction Plant Fitters' Section, Unit 116, Grange Way, Baldoyle Industrial Estate, Baldoyle, Dublin D13 CA48.
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