Remove and replace heavy goods and public service vehicle chassis units and components

Business Sectors (Suites): Maintenance and Repair - Heavy Goods and Public Service Vehicles
Developed by: IMI
Approved on: 30 Mar 2021


This standard is about removing and replacing heavy goods and public service vehicle units and components where dismantling and re-assembly of chassis systems is required. It is also about evaluating the performance of replaced units and components. The units and components concerned are those not replaced as part of normal routine vehicle maintenance (servicing) activities.

Performance criteria

You must be able to:

P1 use suitable personal and vehicle protective equipment throughout all removal and replacement activities
P2 support your removal and replacement activities by reviewing:

P2.1 vehicle technical data
P2.2 removal and replacement procedures
P2.3 legal requirements
P3 prepare the vehicle, vehicle systems and work area for safe working procedures 
P4 prepare, check and use all the equipment required following manufacturers' instructions
P5 carry out all removal and replacement activities following;

P5.1 manufacturers' instructions
P5.2 your workplace procedures
P5.3 health, safety and environmental requirements
P6 work in a way which minimises the risk of:

P6.1 damage to other vehicle systems, units and components
P6.2 contact with leakage and hazardous substances
P6.3 damage to your working environment
P6.4 injury to self and others
P7 ensure replaced chassis units and components conform to the vehicle operating specification and any legal requirements
P8 promptly record and report any additional faults you notice during the course of your work
P9 use suitable testing methods to evaluate the performance of the reassembled system 
P10 ensure the reassembled chassis system performs to the vehicle operating specification and meets any legal requirements prior to return to the customer/driver
P11 ensure your records are accurate, complete and passed to the relevant person(s) within the agreed timescale in the format required
P12 complete all removal and replacement activities within the agreed timescale
P13 promptly report any anticipated delays in completion to the relevant person(s)

Knowledge and Understanding

You need to know and understand:

Legislative and organisational requirements and procedures
K1 the legal requirements relating to the vehicle (including road safety requirements)
K2 the implications on an Operators Licence of not carrying out repairs and inspections correctly
K3 the legislation and workplace procedures relevant to 

K3.1 health and safety
K3.2 the environment (including waste disposal)
K3.3 appropriate personal and vehicle protective equipment
K4 your workplace procedures for

K4.1 recording removal and replacement information
K4.2 the referral of problems
K4.3 reporting delays to the completion of work
K5 the importance of documenting removal and replacement information
K6 the importance of working to agreed timescales and keeping others informed of progress
K7 the relationship between time and costs
K8 the importance of promptly reporting anticipated delays to the relevant person(s)

Use of technical information
K9 how to find, interpret and use sources of information applicable to unit and component removal and replacement within chassis systems
K10 the importance of using the correct sources of technical information
K11 the purpose of and how to use identification codes

Electrical and electronic principles
K12 vehicle earthing principles and methods
K13 electrical and electronic principles associated with chassis systems, including types of sensors and actuators, their application and operation
K14 types of circuit protection and why these are necessary
K15 electrical safety procedures
K16 electric symbols, units and terms
K17 electrical and electronic control system principles
K18 the hazards associated with working on or near high voltage electrical vehicle components

Chassis system operation and construction
K19 how heavy goods and public service vehicle chassis systems and their related units and components are constructed, removed and replaced
K20 how heavy goods and public service vehicle chassis systems and their related units and components operate

K21 how to prepare, check and use all the removal and replacement equipment required

Chassis system unit and component removal and replacement
K22 how to remove and replace heavy goods and public service vehicle chassis system mechanical, electrical, hydraulic and pneumatic units and components
K23 how to select and use gaskets, sealants, seals, fittings and fasteners
K24 how to test and evaluate the performance of replacement chassis system units and components and the reassembled system against the vehicle operating specifications and any legal requirements 
K25 the relationship between testing methods and the chassis system units and components replaced – the use of appropriate test methods
K26 when replacement units and components must meet the original equipment specification (OES) for warranty or other requirements
K27 how to work safely avoiding damage to other vehicle systems, units and components and contact with leakage and hazardous substances
K28 the importance of inspecting the vehicle following any repairs


1. Equipment is:

1.1. hand tools
1.2. special workshop tools
1.3. general workshop equipment
1.4. electrical testing equipment
1.5. interface

2. Testing methods are:

2.1. sensory
2.2. functional
2.3. measurement

3. Units and components are:

3.1. mechanical
3.2. electrical
3.3. hydraulic
3.4. pneumatic

4. Chassis systems are:

4.1. steering
4.2. suspension
4.3. braking
4.4. wheels and tyres

Scope Performance

Scope Knowledge





This section contains examples and explanations of some of the terms used but does not form part of the standard.

Agreed timescales
Examples include: manufacturer's recommended work times, job times set by your company or a job time agreed with a specific customer.

Functional testing
Examples include: use of brake roller tester, dynamometer, suspension activation and interface.

Heavy goods and public service vehicles
These are medium and large goods vehicles, buses and coaches of 3500kgs gross vehicle mass (GVM) and above.

Sensory testing methods
These may include looking, listening, smelling and touching for heat.

Links To Other NOS

External Links

Version Number


Indicative Review Date

31 Mar 2024





Originating Organisation


Original URN


Relevant Occupations

Engineering, Heavy Vehicle Service Technician (Automotive), Vehicle Trades, Bus and Coach Mechanic (semi-skilled), Bus and Coach Mechanic, Bus and Coach Mechelec

SOC Code



Chassis; units; components; heavy goods vehicle; public service vehicle; remove; replace; steering; brakes; suspension; pneumatic; bus; coach;