Focus your study time
The T2 test weights cylinder head, block, valve train, and fuel injection heavily. Emissions is smaller than on A9 because heavy-duty diesel emissions is largely its own certification. Do not spend equal time on every content area — weight your study to match the exam blueprint published by ASE.
The cylinder cutout test
A cylinder cutout test disables individual injectors and watches for RPM change. Know why a weak cylinder shows a smaller RPM drop when it is cut out and why a dead cylinder shows no drop at all. T2 loves questions built around interpreting cutout results on a Cummins ISX or a Detroit DD15.
Airflow and boost calculations
Understand the relationship between boost pressure, exhaust back pressure, and volumetric efficiency. Questions frequently give you three readings and ask what is restricted. Also know how a variable-geometry turbo actuator sticks and what symptoms that produces.