Inspection, Maintenance, and Diagnostic Procedures
Inspection, Maintenance, and Diagnostic Procedures
This domain tests scheduled servicing, checklist inspections, scan-tool use, and systematic diagnosis. Expect questions on service intervals, freeze-frame data, and verification after repair.
Core rules
- Maintenance follows interval and severity: fluids, filters, belts, brakes, tires, battery, and lights. Check tire pressure cold and record tread depth.
- Inspection uses a checklist and calibrated tools: torque wrench, tread gauge, multimeter, and scan tool.
- Diagnostic sequence: verify the concern, gather symptoms and freeze-frame data, inspect visually, test the circuit or system, repair, then verify with a drive cycle.
- DTCs are clues. P0301 means cylinder 1 misfire; causes include spark, fuel, air, compression, or mechanical fault.
- Record freeze-frame and live data before clearing codes. Check technical service bulletins and service information.
- A repair is not complete until the original concern is gone and monitors are ready.
Worked example
A vehicle sets P0301 at idle. Swap the ignition coil from cylinder 1 to cylinder 2. If the misfire moves to P0302, the coil is faulty. If it stays P0301, test the spark plug, injector, intake leak, and compression. Reasoning: a controlled swap isolates an intermittent part without guessing.
Traps
- Clearing codes before recording freeze-frame data.
- Replacing a sensor because the code names its circuit.
- Skipping the post-repair drive cycle.
- Ignoring base engine checks such as compression and vacuum.
- Using a generic scan tool and assuming live data is accurate.