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Truck Diagnostic Guides

Free, expert diagnostic guides for professional truck drivers. Written by mechanics, powered by AI. Find your fault code, fix the problem, get back on the road.

Engine Diagnostics

Common Semi Truck Fault Codes: Top 20 DTCs Every Driver Should Know

Quick reference to the 20 most common truck fault codes across all major makes and engines.

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Semi Truck Check Engine Light Guide: What It Means & When to Stop Driving

Practical guide to understanding your semi truck check engine light — what the different warning levels mean, how J1939 fault codes work, and when to stop vs keep driving.

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Truck Turbocharger Problems: VGT Actuator, Boost Leaks, Shaft Play & Oil Seal Diagnostics

Troubleshoot turbocharger failures on Class 8 diesel engines including VGT actuator diagnostics, boost leak detection, shaft play measurement, and oil seal inspection.

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Exhaust & Emissions

DPF Regeneration Guide: Passive, Active & Forced Regen Explained

Everything you need to know about diesel particulate filter regeneration — passive, active, and forced regen procedures.

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Diesel Exhaust Fluid (DEF) Problems: SCR Issues, NOx Sensor Faults & Inducement Fixes

Complete guide to diagnosing DEF system problems on semi trucks including SCR efficiency codes, NOx sensor failures, DEF quality issues, and how to avoid inducement derates.

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Electrical Systems

Semi Truck Electrical Troubleshooting: Batteries, Alternators, CAN Bus & Parasitic Draw

Comprehensive electrical diagnostics for Class 8 trucks covering battery testing, charging system analysis, parasitic draw isolation, and CAN bus troubleshooting.

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Brake Systems

Semi Truck Air Brake Diagnostics: Compressor, Valves & Leak Detection Guide

Step-by-step air brake system diagnostics covering compressor output, governor operation, valve testing, and systematic leak detection for semi trucks.

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Transmission

Truck Transmission Diagnostics: Eaton Fuller Manual & Allison Automatic Troubleshooting

Diagnose and troubleshoot Eaton Fuller manual, Fuller Advantage, UltraShift, and Allison automatic transmissions with real fault codes and procedures.

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Cooling Systems

Truck Cooling System Diagnostics: Overheating, Water Pump, Thermostat & EGR Cooler Leaks

Complete cooling system diagnostics for diesel trucks including pressure testing, thermostat validation, water pump inspection, EGR cooler leak detection, and coolant analysis.

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Make-Specific

Freightliner Cascadia Diagnostic Guide: Common Problems & Fault Codes

Comprehensive diagnostic guide covering the most common Cascadia issues, fault codes, and repair procedures.

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Peterbilt 389 Troubleshooting: Common Issues & Diagnostic Guide

Troubleshooting guide for the Pete 389 covering engine, electrical, and aftertreatment issues.

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Kenworth T680 Fault Codes & Diagnostic Guide

Fault code reference and diagnostic guide for the Kenworth T680 with PACCAR MX-13 engine.

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Cummins ISX Engine Diagnostics: Fault Codes, Common Failures & Repair Guide

Comprehensive diagnostic guide for Cummins ISX15 engines covering the most common failures, fault codes, and proven repair procedures.

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Detroit DD15 Common Problems: Diagnostic Codes, Oil Leaks & Turbo Actuator Guide

In-depth troubleshooting guide for Detroit DD15 engines covering CPC and ACM fault codes, known oil leak locations, turbo actuator issues, and proven fixes.

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PACCAR MX-13 Troubleshooting: Common Failures, Fault Codes & DAVIE Diagnostics

Complete troubleshooting guide for the PACCAR MX-13 engine covering common failures, key fault codes, and diagnostic procedures using the DAVIE tool.

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Need Help With a Specific Problem?

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