For a complete wiring diagram Refer to Section 8W.Possible CausesFUEL CONTAMINATIONRESTRICTED FUEL SUPPLY LINEFUEL PUMP INLET STRAINER PLUGGEDFUEL PUMP MODULEFUEL INJECTOR(S)1. CHECKING FUEL PRESSUREThe fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.Turn the ignition off.Install a fuel pressure gauge at the engine.Ignition on, engine not running.With a scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).Choose a conclusion that best matches your fuel pressure reading.Below SpecificationGo To 2Within SpecificationGo To 42. RESTRICTED FUEL SUPPLY LINEThe fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.Turn the ignition off.Raise vehicle on hoist, and disconnect the fuel supply line at the fuel pump module.Install special tool #6539 (5/16") #6631(3/8") fuel line adapter and the fuel pressure gauge between the fuel supply line and the fuel pump module.Ignition on, engine not running.With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).Is the fuel pressure within specification?YesVisually and physically inspect the fuel supply lines between the fuel tank and the fuel rail. Repair/replace as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 33. CHECKING THE FUEL INLET STRAINERThe fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.Turn the ignition off.Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.Is the Fuel Inlet Strainer plugged?YesReplace the Fuel Pump Inlet Strainer.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoReplace the Fuel Pump Module.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 4. FUEL PUMP MODULEBefore continuing visually and physically inspect the fuel delivery system for external leaks or damage. Repair / replace as necessary.The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.Turn the ignition off.Install special tool #6539 (5/16") or #6631 (3/8") fuel line adapter.Install the fuel pressure gauge.Start the engine and allow the fuel system to reach maximum pressure.Turn the ignition off. Fuel specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).Using special tool #C4390, Hose Clamp Pliers, pinch the rubber fuel line between the fuel pressure gauge and the engine.Monitor the fuel pressure gauge for a minimum of 5 minutes.The pressure should not fall below 241 kPa (35 psi)Does the fuel pressure drop?YesReplace Fuel Pump Module.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 55. FUEL INJECTOR(S)The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.Remove special tool #C4390.Start the engine and allow the fuel system to reach maximum pressure.Turn the ignition off.Fuel specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).Move special tool #C4390, Hose Clamp Pliers, from between the fuel pressure gauge and the engine to between the fuel pressure gauge and fuel pump module.Monitor the fuel pressure gauge for a minimum of 5 minutes.The pressure should not fall below 241 kPa (35 psi)Does the fuel pressure drop?YesReplace the leaking fuel injectors.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoCheck the fuel for contaminants.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)