How to Prevent Diesel Emission Failures

Diesel emissions systems are designed to keep your trucks compliant with environmental regulations while maintaining optimal engine performance. But when those systems fail, you're not just dealing with downtime — you're looking at potential fines, breakdowns, and costly repairs.

Understanding Diesel Emission Systems

Diesel emission systems are composed of four primary technologies:

Exhaust Gas Recirculation (EGR)

The EGR system reduces nitrogen oxide (NOx) emissions by redirecting a portion of exhaust gases back into the combustion chamber. This lowers combustion temperature and helps meet EPA standards.

Common failure causes:

• Carbon buildup
• Faulty EGR valves
• Leaks in the EGR cooler

Diesel Particulate Filter (DPF)

The DPF captures particulate matter (soot and ash) from exhaust gases. Over time, the filter becomes saturated and must be cleaned through regeneration, a process that burns off accumulated soot.

Common failure causes:

• Missed regen cycles
• Failed sensors
• Excessive idling

Selective Catalytic Reduction (SCR)

The SCR system injects Diesel Exhaust Fluid (DEF) into the exhaust stream to convert NOx into nitrogen and water vapor.

Common failure causes:

• Poor DEF quality
• Crystallized DEF lines
• DEF dosing pump failure

Diesel Oxidation Catalyst (DOC)

The DOC converts hydrocarbons (HC) and carbon monoxide (CO) into less harmful emissions using oxidation reactions.

Common failure causes:

• Oil contamination
• Faulty temperature sensors
• Incomplete combustion

Key Practices to Prevent Emission Failures

1. Stick to a Preventive Maintenance Schedule

Regular maintenance is the cornerstone of emission system longevity. This includes:

• Checking sensor functionality
• Inspecting DEF quality and levels
• Replacing EGR valves when performance degrades
• Cleaning or replacing DPF filters as needed

Keep your maintenance aligned with manufacturer intervals and always perform a post-service system scan to ensure compliance.

2. Minimize Engine Idling

Prolonged idling prevents DPF systems from reaching the necessary temperature for passive regeneration, leading to soot buildup. Encourage drivers to shut off engines during loading or long waits.

Tip: Use idle shut-off timers to automatically reduce idling times.

3. Ensure Quality DEF Usage

Diesel Exhaust Fluid must meet ISO 22241 standards to function properly. Contaminated or low-quality DEF can crystallize in the injection system, leading to SCR failure.

Checklist for DEF care:

• Store DEF between 12°F and 86°F
• Keep containers sealed to avoid contamination
• Use dedicated DEF dispensing equipment

4. Perform Regular Forced Regenerations

If your DPF doesn’t complete its active regeneration due to short trips or low engine loads, forced regeneration may be required. Technicians can override the ECU and initiate regen cycles to prevent clogging.

Warning signs your DPF needs regen:

• Loss of power
• Increased fuel consumption
• Illuminated DPF warning light

5. Monitor ECM and Sensor Data

Modern diesel engines rely on ECMs (Engine Control Modules) to manage emissions. Faulty or outdated ECM software can mismanage regen cycles or DEF dosing.

Use diagnostic software to:

• Monitor NOx sensors
• Review DPF pressure differential
• Track exhaust temperatures

Regular ECM checks are especially important during DOT inspections.

Practical Tips for Fleet Operators

• Train Drivers: Educate drivers on how to recognize early warning signs like power drops, dashboard lights, or erratic fuel consumption.
• Use Fleet Management Tools: Leverage telematics to remotely monitor regen activity, idle time, and emissions status across your fleet.
• Schedule Mobile Maintenance: Scheduling mobile preventive services can reduce downtime and improve compliance.

Addressing Common Fault Codes

Ignoring fault codes is a fast track to costly repairs. Some of the most common include:

• P2002: DPF efficiency below threshold
• P0401: EGR flow insufficient
• P20EE: SCR NOx Catalyst Efficiency below threshold
• P203F: DEF level too low

When these codes appear, prompt diagnostics and corrective action are critical. Resetting codes without resolving the root cause can lead to derating or shutdowns.

Keep Your Emissions in Check

Diesel emissions systems are intricate, but preventing failures doesn’t have to be complicated. By investing in regular maintenance, monitoring system performance, and using high-quality fluids and parts, you can reduce costly downtime and stay compliant with emissions regulations.

If you require EGR cleaning or DPF services in Colorado or Montana, our team at Iron Buffalo is equipped and ready to help.