The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The fuel system is a semi-returnless design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from the engine. A semi-returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

The fuel tank stores the fuel supply. The fuel pump is an electric pump that is attached to the primary fuel tank module assembly. The fuel pump also supplies fuel to the siphon jet pump, also attached to the primary fuel tank module. The siphon jet pump draws fuel from the secondary side of the fuel tank to the primary side of the fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A fuel pressure regulator which is also located in the fuel tank, is attached to the primary fuel tank module. The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned from the fuel filter to the fuel tank by a separate fuel return pipe.

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

Note: 

1. Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool. You should hear the fuel pump turn ON and OFF.

⇒	If the fuel pump does not operate, refer to Fuel Pump Electrical Circuit Diagnosis.

2. Ignition OFF, all accessories OFF, install a CH 48027 Gage . Refer to Fuel Pressure Gage Installation and Removal.
3. Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 384-425 kPa (55-62 psi) and does not decrease more than 34 kPa (5 psi) in 1 minute.

Note: 

•	The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.

•	DO NOT start the engine.

1. Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool and observe the fuel pressure gage while the fuel pump is operating. Verify the fuel pressure is between 384-425 kPa (55-62 psi).

⇒	If the fuel pressure is greater than the specified range, replace the fuel pump module.

⇒	If the fuel pressure is less than the specified range, test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump module.

•	Restricted fuel feed pipe

•	Restricted or plugged strainer

•	Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.

2. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.

⇒	If the fuel pressure decreases more than the specified value, perform the following procedure:

2.1.	Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief.

2.2.	Install the J 37287 Adapter between the fuel feed pipe and the fuel rail.

2.3.	Open the valve on the J 37287 Adapter

2.4.	Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the CH 48027 Gage .

2.5.	Command the fuel pump relay ON and then OFF with a scan tool.

2.6.	Close the valve on the J 37287 Adapter .

2.7.	Monitor the fuel pressure for 1 minute.

⇒	If the fuel pressure decreases more than 34 kPa (5 psi) within the specified time, locate and replace the leaking fuel injector(s).

⇒	If the fuel pressure does not decrease more than 34 kPa (5 psi) within the specified time, replace the fuel pump module.

3. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 minutes.

⇒	If the fuel pressure decreases more than the specified value, replace the primary fuel pump module.

4. Remove the J 37287 Adapter and CH 48027 Gage . Refer to Fuel Pressure Gage Installation and Removal.
5. Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH 48027 Gage . The fuel pressure should not drop off during acceleration, cruise or hard cornering.

⇒	If the fuel pressure drops off, test, inspect, and repair the items listed below. If all items test normal, replace the primary fuel pump module.

•	Restricted fuel feed pipe

•	Restricted or plugged strainer

•	Inspect the harness connectors and the ground circuits of the fuel pump for poor connections

6. If the fuel system tests normal, refer to Symptoms - Engine Controls.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.