Circuit Description
When you turn ON the ignition switch, the Powertrain Control Module (PCM) activates the in-tank fuel pump. The in-tank fuel pump remains ON as long as the engine is cranking or running and the PCM receives reference pulses from the ignition system. If there are no reference pulses, the PCM turns the in-tank fuel pump OFF after about 2-3 seconds.
The electric fuel pump attaches to the fuel sender assembly inside the left fuel tank. The in-tank fuel pump supplies fuel through an in-pipe fuel filter/fuel pressure regulator assembly to the fuel rail. The fuel pump also supplies fuel to the right fuel tank siphon jet pump in order to transfer fuel from the right fuel tank to left fuel tank. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. The fuel pressure regulator, part of the fuel filter, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel returns to the left fuel tank by a separate fuel return pipe.
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 system |
| • | Poor fuel economy |
| • | Loss of power |
| • | Hesitation |
| • | DTCs |
Diagnostic Aids
Important:
• Remove any debris from the PCM\TAC module connector surfaces before
servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets
when diagnosing/replacing the modules. Ensure that the gaskets are installed
correctly. The gaskets prevent contaminate intrusion into the PCM\TAC
modules. • For any test that requires probing the PCM or a component
harness connector, use the Connector Test Adapter Kit J 35616
. Using this kit prevents damage
to the harness/component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
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 condition. |
For an intermittent condition, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step test the fuel pump relay ignition feed circuit.
For relay terminal identification, refer to the table in the Diagnostic Aids.
-
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.
-
Inspect the fuel pump fuse for an open. If the fuse is open, test the circuit for a short to ground.
-
Inspect the fuel pump fuse for an open. If the fuse is open, test the circuit for a short to ground.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 | Inspect 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 using the test lamp J 35616-200 connected to B+. Refer to Diagnostic Aids for terminal identification. Does the test lamp illuminate? | -- | ||
Does the test lamp illuminate? | -- | |||
6 | Jumper the fuel pump relay ignition feed circuit to the fuel pump relay circuit (load) at the underhood electrical center 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 OL? | -- | ||
Repair the open or grounded ignition feed circuit to the relay. 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 feed 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 |
Did you find and correct the condition? | -- | ||
19 | Replace the relay. Refer to Fuel Pump Relay Replacement . Is the action complete? | -- | -- | |
Did you find and correct the condition? | -- | |||
21 |
Important: Inspect for poor electrical connections (within the fuel tank) at the fuel pump/sending unit harness connector before replacing the fuel pump. Replace the fuel pump. Refer to Fuel Tank Fuel Pump Module Replacement . Is the action complete? | -- | -- | |
22 |
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 |
