If timing check procedures are not found on the under-hood label, what should the inspector do?

• A. Refer to the Emission Control Application guide or the manufacturer's service manual.
• B. Use any timing check procedure from any manual.
• C. Skip timing checks.
• D. Adjust timing to match performance.

Answer: (A)

When timing check procedures aren’t on the under-hood label, you must look up the exact procedure and timing specs in the vehicle’s official sources, specifically the Emission Control Application Guide or the manufacturer’s service manual. These documents provide the precise steps, test points, and timing values for that engine and emission-control setup, ensuring you follow the correct process for accurate results.

Relying on a timing procedure from any manual isn’t appropriate because timing methods vary by engine, model, and year, and the emission system relies on those exact specifications. Using the wrong procedure can lead to incorrect timing, which can increase emissions, cause engine misfires, or even damage components.

Skipping timing checks isn’t appropriate because timing is a fundamental part of verifying emissions compliance and engine operation. You need to confirm the correct timing procedure and values before proceeding.

Adjusting timing to match performance without the specified values is risky and often noncompliant. Only apply timing changes that align with the manufacturer’s or EC guide’s approved specs.