Circuit DescriptionThe engine control module (ECM) monitors engine-operating conditions, including the reading of fuel rail pressure, and changes the flow command to either increase (OPEN the fuel pump actuator) or decrease (CLOSE the fuel pump actuator) the fuel supply to the high-pressure pump.
Component LocationThe fuel pump actuator is located on the engine-mounted fuel pump.
Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is operating.
Conditions for Setting the Fault CodesThe ECM has detected that the measured fuel rail pressure has been above the maximum pressure allowed by the fuel pressure relief valve.
Action Taken When the Fault Code is ActiveThe ECM illuminates the red STOP ENGINE lamp immediately when the diagnostic runs and fails. An engine power derate may occur on some engines.
Conditions for Clearing the Fault CodeTo validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop-and-go city driving and steady state highway driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.To validate the repair using a Chassis Dynamometer Test, utilize a routine that incorporates acceleration and motoring events, steady state highway operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the fuel rail pressure returns to normal operation levels and the diagnostic runs and passes.The ECM will turn off the red STOP ENGINE lamp after the diagnostic runs and passes.The ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults.
Shop TalkFault Code 449 is activated when the sensed fuel rail pressure exceeds the normal operating fuel system pressure. It is used to indicate a fuel pressure relief valve which fails to open or does not regulate pressure. Troubleshooting must be focused on inspecting the drain line path of the fuel pressure relief valve for restrictions/obstructions and checking or replacing the fuel pressure relief valve. A restriction in the fuel-drain-to-tank return line can prevent unneeded fuel from exiting the fuel system. Check the fuel drain line restriction from the fuel rail to the tank for damage.
Possible Cause:1) Drain Line Failure2) Fuel pressure relief valve failure3) ECM calibration