P008A sets when the monitored low-pressure fuel-supply condition does not meet the expected pressure or performance requirement according to the vehicle-specific control strategy. Depending on architecture, the decision may be based on direct low-side pressure sensing, pump/control feedback, commanded-versus-observed behavior, inferred supply performance, or combinations of these. Exact monitor logic varies by manufacturer. A critical diagnostic distinction must be maintained: P008A evaluates supply-side hydraulic availability, whereas high-pressure codes address the secondary compression stage.