SUMMARY
A unit designed to develop knowledge of the anti-lock braking system (ABS) fitted to a vehicle and the operation of the main components within the system, and how to deliver constructive reasoning/interpretation of the faults from an identified symptom.
OUTCOMES
1
2
3
Explain the operation of an anti-lock braking system.
Identify for given anti-lock braking system symptoms the possible fault(s).
Demonstrate, using volt and ohmmeters, a test procedure for given anti-lock braking system components to establish their condition.
RECOMMENDED ENTRY
Access to this unit is at the discretion of the centre. However, it would be beneficial if the candidate had achieved the unit Automotive: Braking Systems (Intermediate 2) (2210198).
CREDIT VALUE
1 Credit at Higher.
CORE SKILLS
Information on the automatic certification of any core skills in this unit is published in Automatic
Certification of Core Skills in National Qualifications (SQA, 1999).
Administrative Information
Superclass: XR
Publication date: August 1999
Source:
Version:
Scottish Qualifications Authority 1999
01
© Scottish Qualifications Authority 1999
This publication may be reproduced in whole or in part for educational purposes provided that no profit is derived from reproduction and that, if reproduced in part, the source is acknowledged.
Additional copies of this unit specification can be purchased from the Scottish Qualifications Authority. The cost for each unit specification is £2.50 (minimum order £5.00).

Administrative Information
Superclass: XR
Publication date: August 1999
Source:
Version:
Scottish Qualifications Authority 1999
01
© Scottish Qualifications Authority 1999
This publication may be reproduced in whole or in part for educational purposes provided that no profit is derived from reproduction and that, if reproduced in part, the source is acknowledged.
Additional copies of this unit specification can be purchased from the Scottish Qualifications Authority. The cost for each unit specification is £2.50 (minimum order £5.00).

Acceptable performance in this unit will be the satisfactory achievement of the standards set out in this part of the unit specification. All sections of the statement of standards are mandatory and cannot be altered without reference to the Scottish Qualifications Authority.
OUTCOME 1
Explain the operation of an anti-lock braking system.
Performance criteria a) Correctly identify the main anti-lock braking system components.
b) Correctly explain the operation of the main anti-lock braking system components.
Note on range for the outcome
Components: road speed sensor; exciter ring; hydraulic modulator; warning lamp; electronic control unit; pump; accumulator.
Evidence requirements
Please refer to Evidence requirements for the unit at the end of the Statement of Standards .
OUTCOME 2
Identify for given anti-lock braking system symptoms the possible fault(s).
Performance criteria a) b)
Correctly identify for a given symptom, anti-lock braking system warning lamp fault(s).
Correctly identify for a given symptom, anti-lock braking system operation fault(s).
Note on range for the outcome
ABS warning lamp symptoms: warning light inoperative when ignition is switched on.
Vehicle braking symptoms: vehicle pulling to one side; no anti-lock braking system functions; one wheel continually locks up at any speed when braking.
ABS system operation symptoms: warning light is on and anti-lock braking system is inoperative.
Evidence requirements
Please refer to Evidence requirements for the unit at the end of the Statement of Standards .
Unit specification – Automotive: Anti-Lock Braking Systems (Higher) 3

UNIT Automotive: Anti-Lock Braking Systems (Higher)
OUTCOME 3
Demonstrate using volt and ohmmeters a test procedure for given anti-lock braking system components to establish their condition.
Performance criteria a) b) c) d)
Correctly demonstrate the procedure for measuring the wheel speed sensor air gap.
Correctly demonstrate the procedure for measuring anti-lock braking system components using a voltmeter.
Correctly demonstrate the procedure for measuring anti-lock braking system components using an ohmmeter.
Evaluate accurately anti-lock braking system measurements to establish possible deviations.
Note on range for the outcome
Components: road speed sensor; warning lamp; electronic control unit.
Evidence requirements
Please refer to Evidence requirements for the unit at the end of the Statement of Standards .
EVIDENCE REQUIREMENTS FOR THE UNIT
Outcome 1
Written and/or oral evidence of the candidate’s ability to identify and explain the operation of anti-lock braking system components.
Satisfactory achievement of the outcome will be based on all performance criteria being met. This will be demonstrated by the candidate’s ability to:
PC (a) correctly identify 5 main anti-lock braking system components.
PC (b) correctly explain the operation of 5 main anti-lock braking system components.
Outcome 2
Written and/or oral evidence of the candidate’s ability to identify for given anti-lock braking system symptoms the possible fault(s).
Satisfactory achievement of the outcome will be based on all performance criteria being met. This will be demonstrated by the candidate’s ability to:
PC (a) correctly identify 1 warning lamp fault.
PC (b) correctly identify 3 system operation faults.
Unit specification – Automotive: Anti-Lock Braking Systems (Higher) 4

UNIT Automotive: Anti-Lock Braking Systems (Higher)
Outcome 3
Practical evidence of the candidate’s ability to demonstrate, using volt and ohmmeters, a test procedure for given anti-lock braking system components to establish their condition.
Satisfactory achievement of the outcome will be based on all performance criteria being met. This will be demonstrated by the candidate’s ability to:
PC (a) correctly measure the wheel speed sensor air gap.
PC (b) correctly measure 2 anti-lock braking system components using a voltmeter.
PC (c) correctly measure 1 anti-lock braking system component using an ohmmeter.
PC (d) correctly evaluate 3 readings.
Unit specification – Automotive: Anti-Lock Braking Systems (Higher) 5

UNIT Automotive: Anti-Lock Braking Systems (Higher)
This part of the unit specification is offered as guidance. The support notes are not mandatory.
While the exact time allocated to this unit is at the discretion of the centre, the notional design length is
40 hours.
GUIDANCE ON THE CONTENT AND CONTEXT FOR THIS UNIT
Outcome 1
The candidate should be able to identify and explain how an anti-lock braking system operates and the operation of the following components: speed sensor; excitor ring; modulator; pump; accumulator, ECU; warning lamp.
Outcome 2
The candidate should be able to identify the ABS faults for the given symptoms.
Outcome 3
The candidate should be able to demonstrate the test procedures for certain components in an anti-lock braking system using a voltmeter and ohmmeter and evaluate against set standards.
GUIDANCE ON LEARNING AND TEACHING APPROACHES FOR THIS UNIT
The unit could be taught in a workshop and classroom situation with access to anti-lock braking systems. Some units/components and systems could be made available on which candidates could practice.
Workshop manuals, parts lists, diagnostic equipment and special tools could be made available and any other relevant information required for the task.
GUIDANCE ON APPROACHES TO ASSESSMENT FOR THIS UNIT
Tutors/trainers should use an instrument of assessment appropriate to the type of evidence required.
Examples of instruments of assessment which could be used are as follows:
Outcome 1
Written/graphical exercise.
Outcome 2
Written/graphical exercise.
Outcome 3
Direct observation in conjunction with specified criteria for the given task.
Unit specification – Automotive: Anti-Lock Braking Systems (Higher) 6

UNIT Automotive: Anti-Lock Braking Systems (Higher)
SPECIAL NEEDS
This unit specification is intended to ensure that there are no artificial barriers to learning or assessment. Special needs of individual candidates should be taken into account when planning learning experiences, selecting assessment instruments or considering special alternative outcomes for units. For information on these, please refer to the SQA document Guidance on Special Assessment and Certification Arrangements for Candidates with Special Needs/Candidates whose First
Language is not English (SQA, 1998).
Unit specification – Automotive: Anti-Lock Braking Systems (Higher) 7