For a complete wiring diagram Refer to Section 8W.Possible CausesRESTRICTED FUEL SUPPLY LINEFUEL PUMP INLET STRAINER PLUGGED(N1) FUSED FUEL PUMP CONTROL OUTPUT CIRCUITFUEL PUMP 1. FUEL PUMP OPERATIONIgnition on, engine not running.With a scan tool, actuate the Fuel System test.It may be necessary to use a mechanics stethoscope in the next step.Listen for fuel pump operation at the fuel tank.Does the Fuel Pump operate?YesGo To 2NoGo To 5Stop All Actuations. 2. 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 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).Choose a conclusion that best matches your fuel pressure reading.Below SpecificationGo To 3Within SpecificationTest Complete.Above SpecificationReplace the fuel filter/fuel pressure regulator.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) Stop All Actuations. 3. 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.Turn the ignition off.Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.Install special tool #6539 (5/16") or #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 now?YesRepair/replace fuel supply line as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 4Stop All Actuations. 4. CHECKING 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) 5. (N1) FUSED FUEL PUMP CONTROL OUTPUT CIRCUIT CHECK

Turn the ignition off.Disconnect the Fuel Pump Module harness connector.Using a 12-volt test light connect to ground, probe the (N1) Fused Fuel Pump Control Output circuit at the Fuel Pump Module harness connector.Using a scan tool, actuate the Fuel Pump.Does the test light illuminate brightly during the actuation?YesReplace the Fuel Pump Module.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoRepair the open or short to ground in the (N1) Fused Fuel Pump Control Output circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)