P1259
DTC P1259 High Pressure Fuel Pump PerformanceDescription
The common rail fuel system is comprised of two fuel pressure sections: a suction side between the fuel tank and the fuel supply pump and a high-pressure side between the fuel supply pump and the fuel injectors. Fuel is drawn from the fuel tank via a feed pump and then pumped into the fuel rail by two plungers all of which are internal to the fuel supply pump. This high pressure is regulated by the ECM using the fuel rail pressure (FRP) regulator dependant upon values from the FRP sensor attached to the fuel rail. Under normal conditions the fuel pressure will oscillate slightly due to the characteristics of the two-plunger fuel supply pump system. However if one of the plungers is stuck or the cylinder it rides in is worn out fuel pressure oscillations will be much higher. If the ECM detects that the fuel pressure is oscillating too much continuously for a certain length of time this DTC will set.
Condition for Running the DTC
^ DTCs P0016 P0089 P0091 P0092 P0192 P0193 P0201 - P0204 P0261 P0267 P0270 P0273 P0276 P0264 P0300 P0301 - P0304 P0335 P0336 P0602 P0642 P0643 P1293 and P2146 - P2151 are not set.
^ The desired fuel rail pressure does not vary more than 290 psi (2 MPa).
Condition for Setting the DTC
^ The ECM detects an oscillation of fuel feed quantity is more than a threshold. And oscillations have occurred continuously for 1000 times.
Action Taken When the DTC Sets
^ The ECM illuminates the SVS lamp when the diagnostic runs and fails. Refer to DTC Type Definitions for Action Taken When the DTC Sets - Type C.
Condition for Clearing the DTC
^ Refer to DTC Type Definitions for Condition for Clearing the SVS Lamp DTC - Type C.
Diagnostic Aids
^ A skewed FRP sensor value can set this DTC. The FRP Sensor on the scan tool should read 0.9 to 1.0 volt after the engine has stopped running for a minimum of 30 seconds.
^ Make sure the fuel pressure sensor wiring is not interfering with the crankshaft position camshaft position sensor and fuel injector(s) wire or after-market add-on electrical equipment.
Notice: If the fuel tank is empty or near empty, air might be allowed to go into the fuel system. With air in the fuel system, smooth flow of fuel into the supply pump is interrupted and this DTC may set Perform bleeding of fuel system after refilling.
Test Description
The numbers below refers to the step number on the Circuit System Testing.
8. This step checks for a fuel restriction by determining if a high vacuum is being pulled on the fuel system during normal operation.
9. This step checks for an air leak on the suction side of the fuel system by determining if a vacuum can be pulled when a fuel line is plugged.
Circuit/System Testing DTC P1259
