Fuel Pump Troubleshooting

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Car won't start? Thinking it may be your fuel pump? Below are some resources that may help you to decide if the Fuel pump is the problem or not.

How does power normally get to the fuel pump?
The basics, when everything is working properly…

  1. Turn the Key to Run/on.
  2. A fuel pump relay located inside the Constant Control Relay Module is energized.
  3. This routes power to the "Inertia Fuel Shutoff Switch"
  4. Power is then routed to the Fuel Pump Driver Module.
  5. Along with signals from the PCM the FPDM controls power sent to the fuel pump.

First thing I would want to do is to check the Fuel Shutoff Switch located in the trunk on the left hand side and make sure it has not been latched.

Next thing to do is to check all the fuses that are needed for the pump to run,
In the Battery Junction Box,

  • #14, 20 amp yellow
  • #26, 30 amp green

In the central junction box

  • #2, 20 amp yellow
  • #34, 20 amp yellow

If everything checks out ok then the next thing I would do is check to see if there is power going to the fuel pump.

Disconnect the fuel pump plug located at the back of the fuel tank.
The female side of the plug, that is attached to the body, connects to the fuel pump.
The male side is where we need to check for power to the pump.

We need to put the key to run/on for the pump to get power.

NOTE: the PCM will only supply power to the pump when the key is first turned on for a few seconds. So it is best to check for power as an assistant turns the key to run/on.

Pin 10 +12 VDC Brown and Pink wire
Pin 3 -12 VDC Red and Black wire

If you have 12 volts when the key is put to run/on, then the fuel pump is getting power.
If you cannot hear the pump running then it is most likely defective.
If there is no power to the pump then the next place I would check is for power at the Fuel Cutoff switch. The switch is located in the left rear of the trunk behind the left side trunk panel. You will need to remove the rear trunk panel to get access to the left side and pull it out some to get access to the cutoff switch.

Disconnect the inertia switch and check for 12 VDC on the Dark Green/yellow wire.
If you have power going into the inertia switch, I would next ohm out the switch to make sure it is allowing a connection.

NOTE: The connectors have a pretty small access and it may help to use a small piece of wire, to make sure you are making a connection to the plug for your meter to read.

The inertia switch supplies power to the "Fuel Pump Driver Module". The FPDM is controlled by the PCM and together determines when to run the fuel pump. The FPDM rarely goes out though.

If you do not have power going to the cutoff switch then the problem may be the Constant Control Relay Module. The CCRM is located in the passenger side fender well directly across from the MAF. You will need to remove the tire and pull back the fender skirt to gain access to the CCRM.

I would check for voltage on the CCRM plug at pin #11, 12VDC from the #20 fuel pump fuse, (battery junction box) hot at all times.
Next I would check voltage on the CCRM plug at pin #8 and #10, should have 12 VDC from the #26 fuse, , (battery junction box) hot at all times.
Next I would check voltage on the CCRM plug at pin #12, 12 VDC from the #2 fuse, (central junction box) hot in start and run.
Next I would check for voltage on the CCRM plug at pin #13, 12 VDC from the #34 fuse, (central junction box) hot in start and run.

If any of the CCRM connections are not getting power, then you would need to trace that wire back to see where we are losing the power.

If the CCRM has the correct power then it is most likely the relay inside the CCRM is defective. Sometimes you can insert your meter leads into the back of the plug and test for voltage. We should have 12VDC out from pin #5, Dark Green/Yellow wire. If you cannot get a lead inside the back of the plug, you could use one of the inexpensive test lights that have a sharp probe. This would allow you to insert it into the wire directly test for voltage. No voltage would be consistent with a bad fuel pump relay inside the CCRM.

Just me but if there were any doubts about the CCRM being bad, because it is fairly expensive, I would take a wire from the battery and put it to inertia cutoff switch. This would bypass the CCRM (and all the wiring in between)

To check the wires for continuity you can use a LONG jumper wire between one end of the wire, say for example, pin #5 of the CCRM plug and back to the cutoff switch. Read continuity between cutoff switch and the jumper wire.

NOTE: Just because there is continuity, that does not mean there is a good enough of a connection to carry the amount of current you may need.

To verify the wire is capable of carrying current you can isolate the wire by disconnecting both ends of the wire, jumping one side to power and using a large test lamp, for example a headlamp bulb. Connect one end of the bulb through the wire you are testing and the other end of the bulb to ground. If the lamp comes on with normal brightness then the wire is capable of carrying current.

Below are the wiring diagrams for the Fuel pump system. Click on the image for the full size picture.

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