This module kicks off the Nerd IV failure identification section with a series of real-world case studies, each designed to reinforce diagnostic concepts from earlier in the Nerd Series.

Cases covered include:

• Intermittent stall/no-start conditions traced through ignition and injection signal analysis
• A no-code, non-reproducible no-start solved by testing a combination sensor at elevated RPM
• Scanner data pitfalls, including a misidentified fault code traced to an impossible MAP reading
• EGR port restriction causing misfire with PCM injector disable strategy layered on top
• Optical distributor crank angle sensor breakdown diagnosed via remote scope captures
• A violently bucking Jeep with good inputs and bad outputs pointing to the engine controller
• A no-start 3.8 with spark, fuel, and compression — solved by identifying a broken cam/crank timing relationship on the scope

A recurring theme throughout is the action/reaction diagnostic approach — identifying inputs and outputs to corner problems logically. The module also addresses scope sample rate limitations and how to validate whether a captured signal anomaly is real or an instrument artifact.