GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Aveo 🢒 Engine 🢒 Engine Electrical 🢒 Fuel Pump Electrical Circuit Diagnosis

Circuit Description

When the ignition switch is turned ON, the engine control module (ECM) will supply battery voltage to activate the fuel pump relay and run the in-tank fuel pump. The fuel pump will operate as long as the engine is cranking or running and the ECM is receiving ignition reference pulses.

If there are no reference pulses, the ECM will shut OFF the fuel pump within 2 seconds after the ignition switch is turned ON.

Diagnostic Aids

An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation.

Test Description

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

  1. This step checks for the ECM providing a ground for the operation of the fuel pump relay.

    2.

  2. By confirming that the wiring is OK using steps 2-6, it can be determined that the fuel pump relay is at fault.

    3.

  3. After determining that there is no ground being provided by the ECM to the fuel pump relay, the fault is either the ECM or the wiring between the ECM and the fuel pump relay.

Step

Action

Values

Yes

No

1
  1. Turn the ignition OFF for 10 seconds.
  2. Turn the ignition ON.
  3. Listen for in-tank fuel pump operation.

Does the fuel pump operate for the time specified?

2 seconds

System OK

Go to Step 2

2
  1. Turn the ignition OFF.
  2. Disconnect the fuel pump relay.
  3. Connect a test light between the fuel pump relay connector terminal 85 and ground.
  4. Turn the ignition ON.

Is the test light ON?

--

Go to Step 3

Go to Step 8

3

  1. Turn the ignition OFF.
  2. Connect a test light between the fuel pump relay connector terminal 86 and battery positive.
  3. Turn the ignition ON.
  4. With the ignition ON, the test light should light for 2 seconds.

Is the test light ON?

--

Go to Step 4

Go to Step 9

4
  1. Turn the ignition OFF.
  2. Connect a test light between the fuel pump relay connector terminal 30 and ground.

Is the test light ON?

--

Go to Step 5

Go to Step 11

5

Inspect for an open or short to ground in the wire between the fuel pump relay connector terminal 87 and the fuel pump connector terminal 3.

Is a repair necessary?

--

Go to Step 6

Go to Step 7

6
  1. Repair the wire between the fuel pump relay connector terminal 87 and the fuel pump connector terminal 3.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.

Does the fuel pump operate for the time specified?

2 seconds

System OK

--

7

  1. Replace the fuel pump relay.
  2. Turn the ignition OFF for 10 seconds.
  3. Turn the ignition ON.

Does the fuel pump operate for the time specified?

2 seconds

System OK

--

8

Inspect for an open wire between the fuel pump relay connector terminal 85 and the battery.

Is a repair necessary?

--

Go to Step 13

--

9

Inspect for an open wire between the fuel pump relay connector terminal 86 to the engine control module (ECM) connector terminal B26.

Is a repair necessary?

--

Go to Step 10

Go to Step 12

10
  1. Repair the wire between the fuel pump relay connector terminal 86 to the ECM connector terminal B26.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.

Does the fuel pump operate for the time specified?

2 seconds

System OK

--

11
  1. Replace the fuse Ef10 or repair the wire between the fuel pump relay connector terminal 30 and the battery.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.

Does the fuel pump operate for the time specified?

2 seconds

System OK

--

12
  1. Turn the ignition OFF.
  2. Replace the ECM.
  3. Turn the ignition ON.

Does the fuel pump operate for the time specified?

2 seconds

System OK

--

13
  1. Replace the fuse Ef4 or repair the wire between the fuel pump relay connector terminal 85 and the ignition system.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.

Does the fuel pump operate for the time specified?

2 seconds

System OK

--