The LB 6.6 Duramax series included various models (LBZ, LMM, LLY, etc.) with different systems and horsepower outputs.

Early LB 6.6 models featured a Fuel Injection Control Module (FICM) that presented certain design flaws. In some truck series, the FICM was positioned before the fuel filter. This meant that fuel would flow into the FICM, cool it, and then exit, all before reaching the fuel filter.

This design created a “U-shaped trap” within the FICM, similar to a sink trap. Consequently, any foreign material in the fuel could accumulate and clog the FICM. If you have an early system where fuel enters and exits the FICM from the top, it’s highly susceptible to collecting debris. Therefore, a clogged FICM could be the root cause of a fuel problem in these early applications.