CAT C4.4B Emissions and Aftertreatment
Operation, diagnostic reasoning and practical instruction
About the class
A practical course connecting CAT C4.4B air management and cooled EGR with DOC/SCR operation, DEF delivery and electrical feedback. Learners trace system flows, interpret operating states and use CAT procedures to investigate emissions complaints. The class combines explanations, component identification, demonstrations and diagnostic cases.
Why this training matters
A low-conversion warning can result from fluid quality, dosing, temperature, sensing or an upstream engine problem. Understanding those relationships helps technicians choose a useful test, avoid premature parts replacement and verify the repair. The course follows the supplied module's focus on emissions control, aftertreatment and interactions with other engine systems.
Overall learning outcome
Given applicable CAT service information, a C4.4B engine or documented training substitute, and suitable tools, learners will explain emissions and aftertreatment operation and complete a safe, documented assessment that identifies the next justified test or repair and how the result will be verified.
| CAT C4.4B | 8 outcomes | Hands-on |
|---|---|---|
| NRS, DOC/SCR and DEF systems | Operation, testing and diagnostic decisions | Three practical stations and individual assessment |
Reference application: CAT 450 Backhoe Loader, machine DYN00365; C4.4B engine W7N87011. DOC/SCR is supported by the collected configuration. DPF/regeneration is covered as a conditional comparison; DPF fitment is not confirmed on this machine.
What technicians will be able to do
By the end of the class, learners will be able to:
- Establish the installed configuration
Verify machine and engine identification, select applicable CAT information, and distinguish confirmed DOC/SCR equipment from configuration-dependent DPF equipment. - Explain emissions-control functions
Explain the purposes of NRS, DOC and SCR, and distinguish NOx reduction from oxidation, particulate filtration and soot regeneration. - Trace air and exhaust paths
Trace fresh air, recirculated exhaust and main exhaust, and explain how the NRS cooler, valve, mixer, turbo wastegate and backpressure valve affect operation. - Explain DEF delivery and operating states
Trace supply and return paths and describe metering, heating, injector cooling and key-off purge. Recognize normal prerequisites for dosing. - Interpret sensors and control information
Relate NOx, temperature, pressure, level and quality information to system decisions. Distinguish electrical and communication faults from actual flow faults. - Apply CAT tests and specifications
Select the appropriate procedure and interpret DEF concentration, dosing quantity and NRS cooler leakage using the correct units and complete test conditions. - Collect evidence safely
Preserve diagnostic reports, identify service hazards and complete an approved activity or documented substitute without a critical safety omission. - Justify diagnosis and verify repair
Separate observations from assumptions, select a CAT-supported next test and document how the original complaint and repair result will be checked.
Entry knowledge: diesel combustion, turbocharged air systems, electronic fuel control, basic electrical testing and safe workshop practices. Guided service-tool practice is included.
Course outline
| Module | Covers |
|---|---|
| Configuration and pollutants | Installed systems, control functions and service-information selection |
| Air, exhaust and NRS | Flow paths, cooled EGR, sensors and air-management interactions |
| DOC/SCR and conditional DPF | Oxidation, reduction, filtration and configuration-dependent regeneration |
| DEF delivery and operating states | Metering, fluid quality, heating, cooling and purge |
| Sensors and diagnostic evidence | Schematic use, valid data, commands and associated faults |
| CAT tests and fault cases | Dosing quantity, DEF quality, cooler leakage and low conversion |
| Practical work and assessment | Three stations, individual knowledge check and diagnostic debrief |
What the class includes
Instructor-led learning
CAT-specific explanations, component identification and guided diagnostic discussion.
Practical exercises
Configuration/data, fluid/dosing and schematic/fault-case stations with individual participation.
Instructor and learner resources
Illustrated instructor notes, diagnostic records, case answers and assessment criteria.
Assessment and feedback
Knowledge and practical checks focused on safe methods, evidence and repair verification.
Completion: minimum 16/20 knowledge and 32/40 practical, plus all safety requirements. These are DDS course criteria, not CAT certification. Recorded or simulated activities are identified as such. Delivery is adapted to learner needs and available equipment.
Book this class
Need a custom track?
Combine Jaltest onboarding with emissions, electrical, or HPCR refreshers. We routinely build blended agendas for growing fleets and dealer networks.