2003 Ford Expedition, No Run, No Fuel Pump Operation, Code P0231

This 2003 Ford Expedition came in with a no run condition. A quick check found no fuel pressure and a code P0231 (low voltage on fuel pump monitor circuit). I decided to go to the interior fuse box, where my wiring diagrams, stated the fuel pump relay and fuse are located. There are a couple of covers that have to be removed.

Pull the edge loose at the firewall end and pivot the cover back.

There is a black plastic cover that has to be pulled off of the actual fuse box.


Since my wiring diagrams stated the relay was located in the fuse box, but did not give a specific position, I looked in the owners manual for more info. No luck there. I did some reading and found that there are five internal, non serviceable relays inside the fuse block. My next test would involve locating the output circuit  from the relay.  The wiring diagrams stated that the fuel pump relay output wire was dark green/yellow and it was located in cavity 3 of connector C270K. I placed a jumper wire into the cavity to backprobe the circuit, no volts. Since my backprobe wire is part of a fused jumper wire, I connected battery voltage to the circuit and started the vehicle. This told me that the fuel pump, inertia switch and related wiring were all okay.

I checked fuse #34 with the key on and it had power and was good so that eliminated a faulty pcm relay and related wiring. The next step was to locate the light blue/orange wire in cavity #12 of the C270B connector. It is in the lower right hand corner of the twelve cavity connector just below the connector that I am backprobing in the picture above. When the ignition is turned on the reading was near zero volts and after a few seconds it went to battery voltage. This told me that the pcm was using a ground to energize the fuel pump relay coil. With all of this testing I knew without a doubt that the fuel pump relay that is part of the interior fuse box was faulty.

Disconnect the battery first before removing the fuse block. There is a battery feed cable that also has to be disconnected on the rear edge of the fuse box. It is located under a cover. I have pictures of that at the end of this post. There is only one bolt that holds this fuse block in place.

I unplugged all of the wiring. There are connectors on the top where testing was done and on the edge. Above and below the mounting bolt.

In the rear.

This connector has a slide mechanism. I have my finger in the pull handle for it.

The fuse block removed from the vehicle. You can see the battery terminal post on the lower left edge.

I carefully removed all fuses and relays from the fuse block and laid them out in the order removed.

I took the back cover off of the fuse block and started disassembling it.

Once I had it opened it was easy to see the damage. Slightly right of center.

The damage was even easier to see from the relay side of the board. I feel fairly confident that if this problem would have been caught soon enough, the solder joint could have been repaired or a new relay installed (if one could have been located).

The old fuse block on the left and the new one on the right.

I plugged everything back in and bolted the fuse block in place.

This is the end of the battery cable that I referred to earlier.

The cover for the battery stud on the fuse block.

I put all of the covers back on, cleared the codes and test drove the vehicle. This one is done.

This repair will generally apply to Ford and Lincoln full sized trucks and suv’s in the same years//body style. Check diagrams and component locators before jumping any circuits, as I did.

111 discussions on “2003 Ford Expedition, No Run, No Fuel Pump Operation, Code P0231”

  1. If at all possible you need to see if any codes are stored in the PCM. The vehicle having to be jumped off indicates that the battery is going dead while driving. That would point towards a faulty alternator, fuses, wiring or PCM. The alternator being the most likely culprit. The charging system not working would not cause a sudden engine stall and still crank right back up without the assistance of a jump start. So I think you have two problems.

  2. Sparky – I have an 03 Expedition XLT. About 3-4 months ago it died and wouldn’t start so I replaced the very old battery and it worked fine. Last week after sitting 4 days with a very low tank of gas in 15-25 degree weather it died 5 times on a 12 mile drive. Engine instantly shut off with no warning but my gauges, radio, lights, etc. still worked and I was able to keep starting it and going. After work it didn’t die on the way home and did fine for 2-3 days before a random shutdown in a parking lot. A couple days ago however it died a total of 12 times on that 12 mile drive but this time displaying the charging error and flickering/beeping every few seconds. About a mile from my house it died again but this time needed a jump to get home.

    I didn’t see any damage to the alternator harness wire and I just finished opening up the fusebox in which I found no damage that you show in your other post.

    Thanks a lot for your awesome site!

  3. If the engine runs normally, the rpms will increase when the pedal is depressed but the vehicle will not move, it is very likely that the transmission has failed. You also could have brake or differential problems.

  4. sparky Help my 2003 expedition broke down on me as i arrived at work every time i steped on the gas my front wheels would shake like if you were running your tires on a street full of riges when i got to work my expedition lost power i couldent go foward or reverse i had friends tell me is my transmission? but they aint mechanics so i hope they aint right do you have a clue on what can it be ? thanks spanky

  5. I feel your frustration but what testing have you done and what were the results. I Do Not Recommend testing these circuits with a test light as you can potentially cause damage. Use a quality multimeter.

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