The high pressure lines on a GDI engine can be very dangerous if handled improperly. Here are two different procedures for safely depressurizing a high pressure line on a GDI engine.
Scan tools and OBDII ports have made diagnosing problems much simpler. However, just plugging in a tool will not pinpoint the exact problem. It’s important to convey this point to your customers in a way that helps them to understand the reality of the situation.