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 380-420 kPa (55-61 psi). Excess fuel returns to the fuel tanks. When the engine is stopped, a scan tool in the output controls can turned 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
Fuel Pump Relay Underhood Electrical Center Terminal Identification | |||
|---|---|---|---|
Front of Vehicle | |||
Left Side of Vehicle | Ground | Ignition | Right Side of Vehicle |
Load | Control | ||
The following conditions may have caused the fuel pump fuse to open:
| • | The fuse was 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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For relay terminal identification, refer to the table in the Diagnostic Aids.
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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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Inspect the fuel pump fuse for an open. If the fuse is open, check the circuit for a short to ground. Refer to Body and Accessories/Wiring Systems.
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Inspect the fuel pump fuse for an open. If the fuse is open, check the circuit for a short to ground. Refer to Body and Accessories/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? | -- | ||
3 |
Does the test lamp illuminate? | -- | ||
4 | Probe the ground circuit in the fuel pump relay harness connector with the test lamp J 35616-200 connected to B+. Refer to Diagnostic Aids for terminal identification. Does the test lamp illuminate? | -- | ||
5 |
Does the test lamp illuminate? | -- | ||
6 | Jumper the ignition feed circuit to the fuel pump circuit (load) in the fuel pump relay harness connector using a fused jumper wire. Refer to Diagnostic Aids for terminal identification. Does the fuel pump operate? | -- | ||
7 |
Does the test lamp illuminate? | -- | ||
8 |
Does the test lamp illuminate? | -- | ||
9 |
Does the test lamp illuminate? | -- | ||
10 |
Is the fuse open? | -- | Go to Diagnostic Aids | |
11 |
Does the DMM display the specified value or lower? | 5ohms | ||
Repair the open ignition feed circuit to the relay. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | ||
13 | Repair the open relay ground circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
14 | Repair the open circuit between the fuel pump relay and the fuel pump. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
15 | Repair the open fuel pump ground circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
16 | Repair the short to ground in the fuel pump feed circuit between the relay and the fuel pump. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
17 | Repair the fuel pump relay control circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
18 | Check for poor connections at the relay. Refer to Body and Accessories/Wiring Systems. Did you find and correct the condition? | -- | ||
19 | Replace the relay. Is the action complete? | -- | -- | |
20 | Check the fuel pump harness for damage. Refer to Body and Accessories/Wiring Systems. Did you find and correct the condition? | -- | ||
21 | Replace the fuel pump. Refer to Fuel Sender Assembly Replacement . Is the action complete? | -- | -- | |
22 | Check for a poor connection at the PCM. Refer to Body and Accessories/Wiring Systems. Did you find and correct the condition? | -- | ||
23 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement . Replace the PCM. Is the action complete? | -- | -- | |
24 |
Does the engine start and continue to run? | -- | ||
25 |
Are any DTCs displayed? | -- | Go to the applicable DTC table | |
26 | 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 |
