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Level 4 · Diagnostics Guided Diagnosis Lesson 1/1 advanced 9 min

Using Guided Diagnosis

How to use manufacturer test plans without becoming dependent on them.

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What you will learn

  • Follow a guided test plan
  • Understand the logic behind it
  • Know when to think beyond the plan
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Guided diagnosis walks you through the manufacturer test sequence for a stored fault. It is powerful because it reflects how the system was designed and often accounts for known failure modes and updates.

Its weakness is blind reliance. A guided plan assumes the vehicle is otherwise standard and the conditions match. Your measurements and reasoning must stay in charge: the plan is a guide, not a substitute for understanding how the circuit works.

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Key points

  • Use the plan, but verify each step with your own measurements.
  • Modified or damaged vehicles may fall outside the plan.
  • If the plan and the evidence disagree, trust the measurement and re-check.

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Key points

  • Guided plans encode the manufacturer logic
  • They assume a stock vehicle in good condition
  • Understanding the why beats following blindly
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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