Service function guidePoor Fuel Economy Diagnosis

This service function guide equips professional technicians and experienced DIYers with a structured diagnostic process for identifying the root cause of poor fuel economy in modern vehicles. It begins with a clear explanation of how fuel delivery and consumption are controlled, then moves through preparation, a full step-by-step diagnostic procedure, result verification, and vehicle-specific variations. Readers will learn to systematically eliminate unlikely causes, interpret live data and fuel trim readings, and perform targeted tests that pinpoint the fault without unnecessary parts replacement. After completing the guide, a technician will be able to diagnose excess fuel consumption confidently and recommend the correct repair with supporting evidence.