The Advanced Engine Performance Specialist (L1) test contains 50 scored questions focused on the diagnosis of general powertrain, computerized powertrain controls (including OBD II), ignition systems, fuel and air induction systems, emission control systems and I/M test failures.
Section B of the Task List on computerized powertrain controls states that you should be able to perform the following items on circuits:
Many of the circuit testing questions relate to a sample vehicle using a composite powertrain control system featuring computerized engine control technology used by most manufacturers. This vehicle is described in the Composite Vehicle Type 3 Reference Booklet that is provided both before and at the time of testing.
The Type 3 vehicle was introduced in 2006. This vehicle has several serial data buses and multiple modules. There will be question on the test concerning how different conditions like shorts, opens and changes in resistance can alter serial data bus traffic. You also have to be able to understand the test results from voltage drop, resistance and scope analysis.
Most of all you need to understand how a serial data bus network shares information by just changing voltages over two wires.