Circuit Description
When the ignition switch is ON, the powertrain control module (PCM) activates the in-tank fuel pump. The fuel pump remains ON as long as the PCM receives reference pulses from the ignition system. If there are no reference pulses, the PCM turns the fuel pump OFF after about 2-3 seconds. The pump delivers fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure remains at 379-427 kPa (55-62 psi) while the fuel pump is running. Excess fuel returns to the fuel tank. When the engine is stopped, a scan tool in the output controls function can turn ON the fuel pump.
Improper fuel system pressure results in one or many of the following symptoms:
| • | Cranks but will not run |
| • | Cuts out, may feel like an ignition problem |
| • | Poor fuel economy |
| • | Loss of power |
| • | Hesitation |
| • | Diagnostic trouble codes (DTCs) |
Diagnostic Aids
A fuel pump prime terminal is available at the underhood bussed electrical center (UBEC). Refer to the UBEC cover for terminal location.
The following conditions may have caused the fuel pump fuse to open:
| • | The fuse is faulty. |
| • | There is an intermittent short in the fuel pump power feed circuit. |
| • | The fuel pump has an intermittent internal problem. |
For an intermittent condition, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Command both the ON and OFF states. Repeat the commands as necessary.
-
This step determines if the condition is located on the coil side or the switch side of the circuit.
-
This step verifies that the PCM is providing voltage to the fuel pump relay.
-
This step tests for an open in the ground circuit to the fuel pump relay.
-
This step determines if a voltage is constantly being applied to the fuel pump relay.
-
To gain access to the fuel pump connector, the fuel tank may need to be removed.
-
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.
-
Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.
-
To gain access to the fuel pump connector, the fuel tank may need to be removed.
-
Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | Go to Step 2 | |
Does the fuel pump turn ON and OFF? | Go to Diagnostic Aids | Go to Step 3 | |
With a scan tool, command the fuel pump relay ON and OFF. Do you hear a click when you command the fuel pump relay ON and OFF? | Go to Step 9 | Go to Step 4 | |
Does the test lamp turn ON and OFF? | Go to Step 5 | Go to Step 6 | |
Does the test lamp turn ON and OFF? | Go to Step 19 | Go to Step 22 | |
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 8 | |
7 |
Did you find and correct the condition? | Go to Step 27 | Go to Step 26 |
8 |
Did you find and correct the condition? | Go to Step 27 | Go to Step 20 |
9 | Turn ON the ignition, with the engine OFF. Does the fuel pump operate continuously? | Go to Step 10 | Go to Step 11 |
10 |
Does the fuel pump operate continuously? | Go to Step 21 | Go to Step 25 |
11 | Is the fuel pump fuse open? | Go to Step 12 | Go to Step 14 |
Did you find and correct the condition? | Go to Step 27 | Go to Step 13 | |
Is the fuel pump fuse open? | Go to Step 24 | ||
14 |
Does the test lamp illuminate? | Go to Step 15 | Go to Step 23 |
Connect a 20 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 19 | Go to Step 16 | |
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 27 | Go to Step 17 | |
|
Important: Visually and physically 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 27 | Go to Step 18 | |
18 | Inspect for poor connections at the fuel pump. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 24 |
19 | Inspect for poor connections at the fuel pump relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 25 |
20 | Inspect for poor connections at the harness connector of the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 27 | Go to Step 26 |
21 | 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 27 | -- |
22 | Repair the open fuel pump relay ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 27 | -- |
23 | Repair the battery voltage circuit of the fuel pump relay switch. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 27 | -- |
24 |
Important: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.
Did you complete the replacement? | Go to Step 27 | -- |
25 | Replace the fuel pump relay. Did you complete the replacement? | Go to Step 27 | -- |
26 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 27 | -- |
27 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
