Toyota Highlander Service Manual: Ignition system (2AZ-FE)

Ignition

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On-vehicle inspection

NOTICE: In this section, the terms "cold" and "hot" refer to the temperature of the coils. "Cold"means approximately -10 C (14 F) to 50 C (122 F). "Hot" means approximately 50 C (122 F) to 100 C ...

More about Toyota Highlander:

Symptom simulation
HINT: The most difficult case in troubleshooting is when no problem symptoms occur. In such cases, a thorough customer problem analysis must be carried out. A simulation of the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be carried ...