Diagnostic Procedure

Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.6L DEVILLE & SEVILLE article. After performing Diagnostic System Check - Engine Controls, go to next step.
If fuel injector coil test has been performed, go to next step. If fuel injector coil test has not been performed, perform fuel injector coil test. See FUEL INJECTOR COIL TEST .

NOTE: DO NOT perform this test if the Engine Coolant Temperature (ECT) is above 201°F (94°C).

Observe the ECT parameter on the scan tool. Does the scan tool indicate that the ECT parameter is less than 201°F (94°C)? If yes, go to next step. If no, allow engine to cool below 201°F (94°C), then go to next step.

NOTE: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.

Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gauge. See FUEL SYSTEM PRESSURE RELEASE . Turn ON the ignition, with the engine OFF. Command the fuel pump ON using a scan tool. The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Observe the fuel pressure gauge, with the fuel pump commanded ON. Is the fuel pressure 41-47 psi (284-325 kPa)? If yes, go to next step. If no, see FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.6L DEVILLE & SEVILLE article.

NOTE: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Monitor the fuel pressure gauge for one minute. Does the fuel pressure decrease by more than 5 psi (34 kPa)? If yes, see FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4.6L DEVILLE & SEVILLE article. If no, go to next step.
Using a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu. Select an injector to be tested. Press Enter. This will prime the fuel system. Record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure stabilizes. This is the first pressure reading. Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure. Record the fuel pressure indicated by the fuel pressure gauge after the fuel injector has stopped pulsing. This is the second pressure reading. Press Enter again to bring you back to the Select Injector screen. Repeat for each fuel injector. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Does any fuel injector have a pressure drop value that is either higher than the average pressure drop or lower than the average pressure drop by 1.5 psi (10 kPa)? If yes, go to next step. If no, see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 4.6L DEVILLE & SEVILLE article.
Replace the affected fuel injectors. See FUEL RAIL & INJECTORS under FUEL SYSTEMS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. After repairs, go to next step.
Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 4.6L DEVILLE & SEVILLE article.