GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 Fuel Pump Electrical Circuit Diagnosis

Circuit Description

When you turn ON the ignition switch, the control module enables the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

The electric fuel pump is attached to the fuel sender assembly inside the left fuel tank. The in-tank fuel pump supplies fuel through a fuel feed pipe, a fuel filter/fuel pressure regulator assembly, to the fuel rail. The fuel pump supplies fuel to the siphon jet pump of the right fuel tank. This allows the pump to transfer fuel from the right fuel tank to the left fuel tank. The fuel pump provides fuel at a pressure that is above the pressure needed by the fuel injectors. The fuel pressure regulator, part of the fuel filter, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel returns to the left fuel tank by a separate fuel return pipe.

Diagnostic Aids

Fuel Pump Relay Underhood Electrical Center Terminal Identification

Front of Vehicle

Left Side of Vehicle

Ground

Ignition

Right Side of Vehicle

Fuel Pump Supply

Control

The following conditions may have caused the fuel pump fuse to open:

    • The fuse was faulty.
    • There is an intermittent short in the power feed circuit of the fuel pump.
    • The fuel pump has an internal intermittent condition.

For an intermittent condition, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Command the ON and the OFF states. Repeat the commands as necessary.

  2. This step determines if the condition is located on the coil side, or on the switch side of the circuit.

    3.

  3. This step verifies that the powertrain control module is providing voltage to the fuel pump relay.

    4.

  4. This step tests for an open in the ground circuit to the fuel pump relay.

    5.

  5. This step determines if a voltage is constantly being applied to the fuel pump relay.

    6.

  6. This step tests for a grounded supply circuit between the fuel pump relay and the harness connector of the fuel pump.

    7.

  7. This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.

    8.

  8. This step determines if the fuel pump relay is causing the condition. Use the appropriate-size fused jumper wire.

  9. This step tests for an open, or for excess resistance in the supply circuit between the relay and the harness connector of the fuel pump.

    10.

  10. Inspect the fuel pump ground circuit thoroughly. Corrosion or a poor connection may cause the fuel pump stop operating.

    11.

  11. This step inspects for a poor connection or for corrosion at the fuel pump harness connector which may cause the condition.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the fuel pump relay ON and OFF.

Does the fuel pump turn ON and OFF?

Go to Diagnostic Aids

Go to Step 3

3

With a scan tool, command the fuel pump relay ON and OFF.

Do you hear a click if you command the fuel pump relay ON and OFF?

Go to Step 9

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the fuel pump relay.
  3. Turn ON the ignition, with the engine OFF.

    4. Important: Refer to Diagnostic Aids for fuel pump relay terminal identification.

  4. Probe the control circuit of the fuel pump relay with a test lamp connected to ground.
  5. With a scan tool, command the fuel pump relay ON and OFF.

Does the test lamp turn ON and OFF?

Go to Step 5

Go to Step 6

5

  1. Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the fuel pump relay.
  2. With a scan tool, command the fuel pump relay ON and OFF.

Does the test lamp turn ON and OFF?

Go to Step 19

Go to Step 22

6

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 8

7

Test the control circuit of the fuel pump relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 26

8

Test the control circuit of the fuel pump relay for a short to ground, or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 20

9

Turn ON the ignition, with the engine OFF.

Does the fuel pump operate continuously?

Go to Step 10

Go to Step 11

10
  1. Turn OFF the ignition.
  2. Disconnect the fuel pump relay.
  3. Turn ON the ignition, with the engine OFF.

Does the fuel pump operate continuously?

Go to Step 21

Go to Step 25

11

Is the fuel pump fuse open?

Go to Step 12

Go to Step 14

12

  1. Test the supply voltage circuit of the fuel pump for a grounded circuit between the fuel pump fuse and the fuel pump. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
  2. Replace the fuel pump fuse if necessary.

Did you find and correct the condition?

Go to Step 27

Go to Step 13

13

  1. Install all disconnected components.
  2. Install a new fuel pump fuse.
  3. With a scan tool, turn ON the fuel pump.

Is the fuel pump fuse open?

Go to Step 24

Go to Intermittent Conditions

14
  1. Turn OFF the ignition.
  2. Disconnect the fuel pump relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery voltage circuit of the fuel pump relay switch with a test lamp connected to ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 23

15

Connect a 20-amp fused jumper wire between the battery voltage circuit of the relay switch and the supply voltage circuit of the fuel pump.

Does the fuel pump operate?

Go to Step 19

Go to Step 16

16

Test the supply voltage circuit of the fuel pump for an open, or for high resistance between the relay and the fuel pump harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 17

17

Important: Inspect the ground circuit for tightness, for corrosion on terminals, or for damage to the wiring harness.

Test the ground circuit of the fuel pump for an open, or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 18

18

Inspect for poor connections at the harness connector of the fuel pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 24

19

Inspect for poor connections at the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

20

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 26

21

Repair the supply voltage circuit of the fuel pump for a short to voltage. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

22

Repair the open ground circuit of the fuel pump relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

23

Repair the battery voltage circuit of the fuel pump relay switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

24

Important: Before replacing the fuel pump, inspect for bad connections at the fuel pump, and within the fuel tank.

  1. Replace the fuel pump. Refer to Fuel Sender Assembly Replacement .
  2. Replace the fuel pump fuse if necessary.

Did you complete the replacement?

Go to Step 27

--

25

Replace the fuel pump relay.

Did you complete the replacement?

Go to Step 27

--

26

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 27

--

27

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2