Fuel Pump Electrical Circuit Diagnosis

FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS

CIRCUIT DESCRIPTION
When you turn ON the ignition switch, the control module energizes the fuel pump relay which powers the fuel pump ON. The pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

DIAGNOSTIC AIDS
The following conditions may have caused the fuel pump fuse to open:
- The fuse is faulty.
- There is an intermittent short to ground in the fuel pump battery voltage circuit.
- The fuel pump has an intermittent internal condition.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

TEST DESCRIPTION

Step 1 - Step 14:

Step 15 - Step 27:

The numbers below refer to the step numbers on the diagnostic table.
2. Command both the ON and OFF states. Repeat the commands as necessary.
3. This step determines if the condition is located on the coil side or the switch side of the fuel pump relay.
4. This step verifies that the powertrain control module (PCM) is providing voltage to the control circuit of the fuel pump relay.
5. This step tests for an open in the ground circuit to the fuel pump relay.
6. This step determines if a voltage is constantly being applied to the control circuit of the fuel pump relay.
13. 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.
15. Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.
17. Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.