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.
Sparky,
Thank you so much for your time to create blog, I was able to review and gain confidence from your blog and took matters into my own hands, after replacing fuel pump and spark-plugs I had to reseach online to figure out the problem, once again thank you so much. Mero in SoCal.
Plug and play. No flash required.
I have the no crank, no start issue with my 03 Expy. With all the issues that they had, I decided just to purchase the box and get it over with. The question I have is, does the new box need reprogrammed (part #3L1Z-14A068-AA).
I was told by the parts guy that Ford would have to flash this box after install.
It has been a while since I have done one of these, but I think the battery cable may have to be removed from the stud on the fuse box before it will pull towards the seat enough to access the rear of the fuse box. The fuse box has to lift off of the mounting stud and slide towards the rear of the vehicle before the hinge tab at the front of the fuse box will clear the sheet metal.
I have seen the shorted wires at the a/c lines for the alternator and have done a post on it. I does not seem to be relevant to the short for the #1 fuse. At least according to the wiring diagram that I looked at.
http://www.sparkys-answers.com/2009/10/2003-ford-expedition-charge-light-on.html
Having same root issue p0231 – intermittent stalling. After pulling all connectors on front and side and nut – can’t get board out. It still has the 3 connectors in the back and the battery line conected but i can’t seem to get it out of position to pull the rest of the connectors off and the battery line cover off. How does the standoff hold in place?
Any help is greatly appreciated.
ps Jeff C – I also had the same issue as you and it turned out to be a short on the wire harness between the alternator and the battery. It was intermittent and periodically caused the battery voltage to go all over the place. If you follow the harness back from the alternator, there a two takoffs. One goes towards the bottom of the battery holder and ties into the washer fluid reservoir through other connectors. My intermittent short was in this one as it rested on the top of one of the metal a/c lines. …of course FIRST I replaced the alternator, battery and re-programmed the pcm to no avail (as per my dealers suggestion and benefit…)