DIAGNOSTIC MANUAL
10.3. GRAPH 3: LUG DOWN TEST (ENGINE SPEED, FRP, AND FRPD)
1. Fuel Rail Pressure Desired (FRPD)
(psi) [Orange]
2. Engine load (percent) [Green]
3. Accelerator Pedal Position 1
(APP1) (percent) [Blue]
4. Fuel Rail Pressure (FRP) (psi)
[Red]
Figure 28
Graph 3: Lug Down Test (Engine Speed, FRP, and FRPD)
Graph Analysis:
This graph shows a fuel management system operating as designed. This test does not give pass or fail results.
It only allows the user to validate Fuel Rail Pressure (FRP) and Fuel Rail Pressure Desired (FRPD) signal
values under load. As engine rpm increases, Fuel Rail Pressure (FRP) should steadily increase. Low FRP will
cause low Intake Manifold Pressure (IMP). Diagnose low FRP concerns before diagnosing low IMP concerns.
124
https://www.truck-manuals.net/
