Volt

Fuel System Diagnosis

The engine control module (ECM) supplies voltage to the fuel pump control module when power up is commanded. The voltage from the ECM to the fuel pump control module remains active for two seconds, unless the engine is in Crank or Run. While this voltage is being received, the fuel pump control module closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank fuel pump module in order to maintain the desired fuel line pressure.

The fuel system is an electronic returnless on-demand design. A 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. An electric turbine style fuel pump attaches to the fuel tank fuel pump module inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel feed pipe to the fuel injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel tank fuel pump module. The function of the venturi pump is to fill the fuel tank fuel pump module reservoir. The fuel tank fuel pump module contains a reverse flow check valve. The check valve maintains fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

For equivalent regional tools, refer to Special Tools : Diagnostic Tools .

Note: 

1. Vehicle in Service Mode, observe the DTC information with a scan tool. DTC P018B, P018C, P018D, P0231, P0232, P023F, P025A, P0562, P0563, P0601-P0604, P0606, P062F, P0641, P064A, P06A6, P1255, P2534, P2635, U0073, U0100 or U0140 should not be set.

⇒	If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Vehicle OFF, all accessories OFF, install a CH 48027 Gauge . Refer to Fuel Pressure Gauge Installation and Removal

Note: DO NOT perform the Fuel System Diagnosis if the engine coolant temperature is above 60°C (150°F). High fuel pressure readings may result due to hot soak fuel boiling. With the engine OFF, the fuel pressure may increase beyond the pressure relief regulator valve's setting point of 690 kPa (100 psi) ± 5 percent.

3. Vehicle in Service Mode, command the Fuel Pump Enable ON with a scan tool.
4. Verify the fuel pressure is between 379-427 kPa (55-62 psi) with the fuel pump operating.
5. Engine running at normal operating temperature, the Fuel Pump Control Module Fuel Pressure Sensor parameter should read between 296-310 kPa (43-45 psi).

Note: 

•	The scan tool Fuel Pump Enable may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.

•	DO NOT start the engine.

1. Vehicle in Service Mode, command the Fuel Pump Enable ON with a scan tool.
2. Observe the fuel pressure gauge while the fuel pump is operating. Verify the fuel pressure is between 379-427 kPa (55-62 psi).

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

•	Restricted fuel feed pipe

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

3. 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:

3.1.	Vehicle OFF, relieve the fuel pressure.

3.2.	Install the EN 37287 Adapter between the fuel feed pipe and the fuel rail.

3.3.	Open the valve on the EN 37287 Adapter .

3.4.	Vehicle in Service Mode, command the Fuel Pump Enable ON with a scan tool and bleed the air from the CH 48027 Gauge .

3.5.	Command the Fuel Pump Enable ON and then OFF with a scan tool.

3.6.	Close the valve on the EN 37287 Adapter .

3.7.	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 tank fuel pump module.

4. Relieve the fuel pressure to 69 kPa (10 psi).
5. 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 fuel tank fuel pump module.

6. Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH 48027 Gauge . 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 fuel tank fuel pump module.

•	Restricted fuel feed pipe

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

7. If the fuel system tests normal, refer to Symptoms - Engine Controls , Fuel Injector Solenoid Coil Test , and Fuel Injector Balance Test .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.