Emissions & Engine Management
EGR systems, DPF regeneration, DEF/SCR systems, engine ECM, fault codes, and automatic idle shutdown.
- Explain EGR system operation and its role in NOx reduction
- Describe DPF regeneration types - passive, active, and stationary
- Identify DEF/SCR system components and common failure modes
- Interpret engine fault codes and ECM diagnostic procedures
- Explain automatic idle shutdown systems and fuel efficiency features
Lesson 1
EGR & Diesel Particulate Filter Systems
Exhaust Gas Recirculation
The EGR (Exhaust Gas Recirculation) system reduces NOx (nitrogen oxide) emissions by routing a portion of exhaust gas back into the intake manifold. Exhaust gas is inert - it does not burn - so it lowers peak combustion temperatures. Lower temperatures mean less NOx formation.
EGR Components
The EGR system includes the EGR valve (controls flow), EGR cooler (reduces exhaust temperature before re-entry), and EGR mixer (blends exhaust with fresh intake air). A faulty EGR valve that sticks open causes rough idle and excessive soot. One that sticks closed increases NOx emissions and may trigger fault codes.
Diesel Particulate Filter
The DPF (Diesel Particulate Filter) traps soot particles from the exhaust stream. Over time, soot accumulates and must be burned off through regeneration. There are three regeneration types.
Passive Regeneration
Automatic - occurs during normal operation
Exhaust temperatures above 350 C naturally burn soot
Happens during sustained heavy load
No operator action needed
Active Regeneration
ECM-initiated - soot level reaches threshold
ECM injects extra fuel to raise exhaust temperature
Machine can continue operating
Indicator light may illuminate
Stationary (Parked) Regen
Manual - soot level is critical
Machine must be parked and stationary
Operator initiates through dash controls
Takes 20-40 minutes to complete
DPF Regeneration Safety
During stationary regeneration, exhaust temperatures exceed 600 C. Keep the machine away from combustible materials, buildings, and personnel. Never interrupt a regeneration cycle once started.
EGR recirculates exhaust gas to lower combustion temperature and reduce NOx emissions. The DPF traps soot particles and burns them off through regeneration - passive (automatic), active (ECM-initiated), or stationary (manual, machine parked).