Circuit Description
When the ignition switch is ON, the 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 |
| • | 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.
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Refer to the thumbnail wiring schematic for the proper terminal identification.
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The test lamp only illuminates for two seconds even though the scan tool commanded position is ON. You will have to command the fuel pump OFF then ON to re-enable the PCM fuel pump control.
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The fuel pump harness connector can be accessed between the framerail and the fuel tank.
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Inspect the fuel pump fuse for an open. If the fuse is open, inspect the circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems.
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Inspect the fuel pump fuse for an open. If the fuse is open, inspect the circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 | Check the fuel pump fuse. Is the fuse open? | -- | ||
Does the test lamp illuminate? | -- | |||
4 | Probe the fuel pump relay ground circuit at the underhood electrical center with the test lamp J 35616-200 connected to B+. Refer to the thumbnail wiring schematic for the proper terminal identification. Does the test lamp illuminate? | -- | ||
Does the test lamp illuminate? | -- | |||
6 |
Important: Ignition must be ON before performing this step. Jumper the fuel pump relay battery feed circuit to the fuel pump circuit (load) at the underhood electrical center using a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems. Does the fuel pump operate? | -- | ||
Does the test lamp illuminate? | -- | |||
8 |
Does the test lamp illuminate? | -- | ||
9 |
Does the test lamp illuminate? | -- | ||
10 | Probe the battery feed circuit for the fuel pump relay at the underhood electrical center with the test lamp J 35616-200 connected to B+. Does the test lamp illuminate? | -- | ||
11 |
Does the DMM display the specified value or lower? | 5ohms | ||
Repair the open or grounded battery feed circuit to the relay. Replace the fuel pump fuse if the fuse is open. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | ||
13 | Repair the open relay ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
14 | Repair the open circuit between the fuel pump relay and the fuel pump. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
15 | Repair the open fuel pump ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
16 | Repair the short to ground in the fuel pump relay load circuit between the relay and the fuel pump. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
17 | Repair the fuel pump relay control circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
18 | Inspect for poor connections at the relay (underhood electrical center). Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. Did you find and correct the condition? | -- | ||
19 | Replace the relay. Refer to Fuel Pump Relay Replacement . Is the action complete? | -- | -- | |
Replace the underhood electrical center. Refer to Underhood Fuse Block Replacement in Wiring Systems. Is the action complete? | -- | -- | ||
21 |
Is the Fuel Pump fuse open? | -- | Go to Diagnostic Aids | |
22 | Inspect for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. Did you find and correct the condition? | -- | ||
23 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
24 |
Did you find and correct the condition? | -- | ||
25 |
Important: Inspect for poor electrical connections (within the fuel tank) at the fuel pump/sending unit harness connector before replacing the fuel pump. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. Replace the fuel pump. Refer to Fuel Tank Fuel Pump Module Replacement . Is the action complete? | -- | -- | |
26 |
Does the engine start and continue to operate? | -- | ||
27 |
Are any DTCs displayed? | -- | Go to the applicable DTC table | |
28 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
