Engine diagnostics is the starting point when a fault can be described but its cause is still unknown. Changes in starting, idle quality, power or fluid levels can involve several systems. This area moves from a complaint to a testable cause, distinguishing electrical deviations from mechanical condition or problems with air and fuel supply.
The sequence of checks follows the circumstances, service history and initial measurements. A fault code is treated as a clue, not an instruction to replace a particular part. The findings explain the deviations and proposed next steps. Specialist diesel equipment work and confirmed mechanical repairs have their own service areas in the catalogue.