GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 XLR 🢒 Engine 🢒 Engine Controls - 4.6L (LH2) 🢒 Fuel Pump Electrical Circuit Diagnosis

Circuit Description

When you turn the ignition switch ON, the control module energizes the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain ON as long as the engine is running or cranking and the control module is receiving reference pulses. If no reference pulses are present, the control module de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped.

Diagnostic Aids

Listen for an audible hiss from the fuel pump when the fuel pump relay is commanded ON. A vibration in the fuel feed line when the fuel pump relay is commanded ON indicates that the fuel pump is operating.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

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

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

    2.

  2. This step verifies that the fuel pump fuse is providing voltage to the fuel pump relay.

    3.

  3. This step jumps the fuel pump relay in order to activate the fuel pump.

    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.

Fuel Pump Electrical Circuit Diagnostic

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn ON the ignition, with the engine OFF.
  2. 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. Remove the fuel pump relay.
  3. Probe the ground circuit for the fuel pump relay with a test lamp connected to battery voltage.

Did the test lamp illuminate?

Go to Step 21

Go to Step 16

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 17

Go to Step 20

7

Is the fuel pump fuse open?

Go to Step 8

Go to Step 10

8
  1. Disconnect the fuel pump harness in-line connector located near the fuel tank. Refer to Power and Grounding Connector End Views .
  2. Test the supply voltage circuit of the fuel pump for a grounded circuit. Refer to Wiring Repairs and Connector Repairs .
  3. Replace the fuel pump fuse, if necessary.

Did you find and correct the condition?

Go to Step 21

Go to Step 9

9
  1. Lower the left fuel tank, if necessary. Refer to Fuel Tank Fuel Pump Module Replacement - Left Side .
  2. Test the fuel tank electrical harness for damage or for a grounded circuit. Refer to Circuit Testing and Wiring Repairs .
  3. Replace the fuel pump fuse, if necessary.

Did you find and correct the condition?

Go to Step 21

Go to Step 15

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 positive voltage circuit of the fuel pump relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 18

11

Connect a 15-amp fused jumper wire between the battery positive voltage circuit and the fuel pump supply circuit of the fuel pump relay.

Does the fuel pump operate?

Go to Step 16

Go to Step 12

12
  1. Disconnect the fuel pump harness in-line connector located near the fuel tank. Refer to Power and Grounding Connector End Views .
  2. Test the supply voltage circuit of the fuel pump for an open or for high resistance between the fuel pump relay and the in-line connector. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 21

Go to Step 13

13

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

Test the ground circuit of the fuel pump for an open or for high resistance between the body pass through connector and the ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 21

Go to Step 14

14
  1. Lower the left fuel tank. Refer to Fuel Tank Fuel Pump Module Replacement - Left Side .
  2. Test for an intermittent and poor connection at the fuel tank module connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 21

Go to Step 19

15

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

Is the fuel pump fuse open?

Go to Step 19

Go to Diagnostic Aids

16

Test for an open or an intermittent condition in the fuel pump relay ground circuit. Refer to Circuit Testing , Wiring Repairs , Testing for Intermittent Conditions and Poor Connections , and Connector Repairs .

Did you find and correct the condition?

Go to Step 21

Go to Step 20

17

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

Did you complete the repair?

Go to Step 21

--

18

Repair the battery positive voltage circuit of the fuel pump relay for an open. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 21

--

19

Important: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.

  1. Replace the left fuel tank module. Refer to Fuel Tank Fuel Pump Module Replacement - Left Side .
  2. Replace the fuel pump fuse, if necessary.

Did you complete the replacement?

Go to Step 21

--

20

Replace the fuel pump relay.

Did you complete the replacement?

Go to Step 21

--

21

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2