BG Technical Knowledge Center

Diesel Aftertreatment Knowledge Center

Practical technical articles, diagnostic procedures and system guides covering NOx sensors, DEF dosing, SCR, DOC and DPF systems for the independent automotive aftermarket.

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Find system fundamentals, diagnostic guidance and component-level technical information.

DPF & DOC Systems

Filter operation, soot and ash management, regeneration and exhaust restriction diagnosis.

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SCR & DEF Systems

NOx reduction, DEF delivery, dosing control, catalyst operation and common SCR faults.

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Sensors & Diagnostics

NOx, EGT, PM and pressure-sensor functions, live-data interpretation and fault diagnosis.

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DPF Regeneration

Passive, active, forced and off-vehicle regeneration procedures and service decisions.

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SCR Troubleshooting

A system-level approach to dosing faults, sensor errors, catalyst efficiency and inducement.

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Latest technical articles

Start with the fundamentals

Core system guides for diesel aftertreatment technicians and workshops.

01

Diesel Aftertreatment System Overview

How DOC, DPF, SCR, DEF dosing and sensors work together as one emission-control system.

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02

What is a DPF System?

How a diesel particulate filter system works, its components and warning signs.

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03

Diesel DPF Regeneration Explained

Passive, active, forced and off-vehicle regeneration — and why regeneration fails.

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04

DPF vs DOC vs SCR

A practical comparison of the three principal aftertreatment stages and what each one controls.

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05

How Selective Catalytic Reduction Works

SCR chemistry, DEF/AdBlue delivery and the role of the SCR catalyst.

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06

Common SCR System Faults

NOx sensor, doser, pump and catalyst issues and how to diagnose them.

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07

NOx Sensor: Function, Symptoms and Testing

What a NOx sensor does, upstream vs downstream roles, failure symptoms and the test procedure.

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08

NOx Sensor Failure Symptoms and Checks

Symptoms, live-data checks and validation steps to run before replacing a NOx sensor.

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09

P20EE — SCR Efficiency Below Threshold

Why SCR efficiency drops, catalyst testing and the parts needed to repair P20EE.

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10

P229F — NOx Sensor Performance

NOx sensor performance-code diagnosis, testing and replacement selection.

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11

P204F — Reductant System Performance

DEF/AdBlue system performance faults, pump pressure and doser inspection.

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12

P2BAD — NOx Sensor Circuit Range / Performance

NOx sensor circuit range fault testing and the right BG replacement.

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