GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 Fuel Pump Electrical Circuit Diagnosis
Table 1: Fuel Pump Electrical Circuit Diagnostic

Circuit Description

The engine control module (ECM) provides a ground to the coil side of the fuel pump relay. When the ignition switch is first turned On, the ECM energizes the fuel pump relay, which applies power to the fuel pump. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the ECM de-energizes the fuel pump relay after 3 seconds.

Diagnostic Aids

Listen for a click when the fuel pump relay operates. When the fuel pump relay is commanded On with the scan tool, the ECM pulses the fuel pump relay ON and OFF several times.

For an intermittent condition, refer to Intermittent Conditions .

Fuel Pump Relay Terminal Identification

FP Motor

FP Control

Ignition 1 Voltage

B+

Front of Vehicle

Test Description

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

  1. Listen for a click when the fuel pump relay operates. When the fuel pump relay is commanded On with the scan tool, the ECM pulses the fuel pump relay ON and OFF several times. Repeat the command 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 tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.

    4.

  4. This step verifies there is battery voltage to the fuel pump relay.

    5.

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

    6.

  6. This step determines if the condition with the circuit is intermittent.

Fuel Pump Electrical Circuit Diagnostic

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. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON 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 with a scan tool.

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

Go to Step 4

Go to Step 14

4

Does the fuel pump operate continuously?

Go to Step 5

Go to Step 6

5
  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 15

Go to Step 18

6

Is the fuse open for the voltage supply circuit of the fuel pump?

Go to Step 7

Go to Step 8

7
  1. Test for a short to ground in the fuel pump supply voltage circuit. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.
  2. Replace the fuel pump fuse if necessary.

Did you find and correct the condition?

Go to Step 19

Go to Step 13

8
  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 9

Go to Step 16

9

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

Does the fuel pump operate?

Go to Step 14

Go to Step 10

10

Test the fuel pump motor circuit for an open or for high resistance. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 11

11

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

Test the ground circuit for an open or for high resistance. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 12

12

Test for an intermittent and for a poor connection 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 19

Go to Step 17

13
  1. Connect all disconnected components.
  2. Install a new fuse.
  3. Command the fuel pump ON with a scan tool.

Is the fuse open?

Go to Step 17

Go to Diagnostic Aids

14

Test for an intermittent and for a poor connection 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 19

Go to Step 18

15

Repair the short to voltage in the fuel pump supply voltage circuit. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

16

Repair the open or high resistance in the battery positive voltage circuit. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

17
  1. Replace the fuel pump.
  2. Replace the fuse if necessary.

Did you complete the replacement?

Go to Step 19

--

18

Replace the fuel pump relay.

Did you complete the replacement?

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2