GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 L300/LW300 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 Fuel Pump Electrical Circuit Diagnosis

Circuit Description

When the ignition is turned ON, the engine control module (ECM) will turn ON the in-tank fuel pump. The in-tank fuel pump will remain ON as long as the engine is cranking or running and the ECM is receiving reference pulses. If there are no reference pulses, the ECM will turn the in-tank fuel pump OFF 2 seconds after the ignition is turned  ON or 2 seconds after the engine stops running.

Diagnostic Aids
    • The following conditions may have caused the fuel pump fuse to open:
       - There is an intermittent short in the fuel pump supply voltage circuit.
       - The fuel pump has an intermittent internal 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 both the ON and OFF states. Repeat the commands as necessary.

    2.

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

    3.

  3. This step verifies that the battery positive is providing voltage is present at the fuel pump relay.

    4.

  4. 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.

    5.

  5. Use the same amperage fuse in the jumper that is used in order to protect the fuel pump circuit.

    6.

  6. Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

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

Does the fuel pump turn ON and OFF?

Go to Diagnostic Aids

Go to Step 3

3

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

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

Go to Step 5

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the fuel pump relay.
  3. Connect a test lamp between the control circuit of the fuel pump relay and the battery positive voltage, switch side of the fuel pump relay.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, command the fuel pump relay ON and OFF.

Does the test lamp turn ON and OFF?

Go to Step 15

Go to Step 17

5

Turn ON the ignition, with the engine OFF.

Does the fuel pump operate continuously?

Go to Step 6

Go to Step 7

6
  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 16

Go to Step 19

7

Is the fuel pump fuse open?

Go to Step 8

Go to Step 10

8
  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 20

Go to Step 9

9

  1. Install all disconnected electrical components.
  2. Install a new fuel pump fuse.
  3. Turn ON the fuel pump with a scan tool.

Is the fuel pump fuse open?

Go to Step 18

Go to Intermittent Conditions

10
  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 side with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 19

11

Connect a 15-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 15

Go to Step 12

12

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

Did you find and correct the condition?

Go to Step 20

Go to Step 13

13

Important: 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 20

Go to Step 14

14

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 20

Go to Step 18

15

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 20

Go to Step 19

16

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 20

--

17

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

Did you complete the repair?

Go to Step 20

--

18

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 Sender Assembly Replacement .
  2. Replace the fuel pump fuse if necessary.

Did you complete the replacement?

Go to Step 20

--

19

Replace the fuel pump relay.

Did you complete the replacement?

Go to Step 20

--

20

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2