GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Corvette 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Fuel Pump Electrical Circuit Diagnosis

Object Number: 383809 Size: MF
Engine Controls Component Views
Fuel Pump, Fuel Level Sensors and Fuel Tank Pressure Sensor
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

When you turn ON the ignition switch, the powertrain control module (PCM) activates the in-tank fuel pump. The in-tank fuel pump remains ON as long as the engine is cranking or running and the PCM receives reference pulses from the ignition system. If there are no reference pulses, the PCM turns the in-tank fuel pump OFF after about 2-3 seconds.

The electric fuel pump attaches to the fuel sender assembly inside the left fuel tank. The in-tank fuel pump supplies fuel through an in-pipe fuel filter/fuel pressure regulator assembly to the fuel rail. The fuel pump also supplies fuel to the right fuel tank siphon jet pump in order to transfer fuel from the right fuel tank to left fuel tank. The fuel pump provides fuel at a pressure 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.

Improper fuel system pressure results in one or many of the following symptoms:

    • Cranks but will not run
    • Cuts out, may feel like an ignition system
    • Poor fuel economy
    • Loss of power
    • Hesitation
    • DTCs

Diagnostic Aids

Important: 

   • Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the module. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM.
   • For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

Fuel Pump Relay Underhood Electrical Center Terminal Identification

Front of Vehicle

Left Side of Vehicle

Ground

Ignition

Right Side of Vehicle

Load

Control

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

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

For an intermittent condition, refer to Symptoms .

Test Description

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

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

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

    3.

  3. Verifies that the powertrain control module is providing voltage to the fuel pump relay.

    4.

  4. 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. Tests for a grounded supply circuit between the fuel pump relay and the fuel pump harness connector.

    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. Tests for an open or excessive resistance in the supply circuit between the fuel pump relay and the fuel pump harness connector.

    10.

  10. Inspect the fuel pump ground circuit thoroughly. A poor connection or corrosion will cause the fuel pump to be inoperative.

    11.

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

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

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 Intermittent Conditions

Go to Step 3

3

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

Do you hear a click when 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. Probe the control circuit of the fuel pump relay with a test lamp that is connected to a good 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
  1. Disconnect the PCM. Refer to Powertrain Control Module Replacement .
  2. 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
  1. Disconnect the PCM. Refer to Powertrain Control Module Replacement .
  2. Test the control circuit of the fuel pump relay for a short to ground or 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 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 that is connected to a good 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 fuel pump 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 high resistance between the fuel pump 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: Visually/physically inspect the ground circuit for being tight, corrosion on terminals, or damage to the wiring harness.

Test the ground circuit of the fuel pump for an open or 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 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 fuel pump relay ground circuit. 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: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.

  1. Replace the fuel pump. Refer to Fuel Tank Fuel Pump Module 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