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Level 4

Diagnostics

OBD-II, DTCs, freeze frame and live data, then a disciplined methodology that finds the cause instead of the symptom.

7 Modules 9 Lessons Level exam

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OBD-II

The standard diagnostic connector, modes, monitors and readiness.

2 Lessons 19 min
  1. 1 OBD-II Basics beginner 9 min
  2. 2 Live Data and Readiness intermediate 10 min
Open module Module quiz

Diagnostic Trouble Codes

How codes are set, pending vs stored, and why a code is a clue.

2 Lessons 22 min
  1. 1 Understanding DTCs intermediate 10 min
  2. 2 From Code to Cause advanced 12 min
Open module Module quiz

Freeze Frame

The photograph of conditions at the moment a fault was stored.

1 Lessons 9 min
  1. 1 Using Freeze Frame intermediate 9 min
Open module Module quiz

Live Data

Interpreting streaming parameters as a system, not a list.

1 Lessons 12 min
  1. 1 Reading Fuel Trims advanced 12 min
Open module Module quiz

Actuator Tests

Commanding outputs to prove wiring and mechanical response.

1 Lessons 10 min
  1. 1 Commanded Actuator Tests advanced 10 min
Open module Module quiz

Guided Diagnosis

Using scan-tool test plans without becoming dependent on them.

1 Lessons 9 min
  1. 1 Using Guided Diagnosis advanced 9 min
Open module Module quiz

Professional Diagnostic Methodology

A repeatable process from customer complaint to confirmed repair.

1 Lessons 12 min
  1. 1 The Five-Step Diagnostic Process advanced 12 min
Open module Module quiz
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Level exam

Pass mark: 75%

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All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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