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.
Thanks for this blog. My fuel system issue is exactly as detailed here. I was able to find a company to order the relay. I will keep you posted. After I disassembled, at first I thought I had done it in vain because the damage was hard to see. After I looked closer at the pins, I could see what could be a solder joint gone cold. And sure enough, when I looked at the relay side, the relay’s casing was slightly melted. I will keep you posted whether I end up buying another panel, or successfully repair this one. The company to get the relay was one mentioned earlier in this thread (Digikey).
If you can find an external type that has the same resistance values and other possible internal electronics, find a wiring diagram and connector identifier and take the time to actually do the modification then yes. But when you consider all of that $250 does not seem that bad. It definitely is not cost effective for me to do that for a customer. I do also want to stress the need for amperage draw testing of the fuel pump as these vehicles age. The last thing you want to do is install a new fuse box and have a faulty fuel pump take it out again.
Hey Sparky, I have an 05 expedition and I’m pretty sure my fuel pump relay is shorting out as shown in your great write up. I hook up a hot wire to the dark green and yellow wire and tried to start it up. It started without hesitation.
Here is my question. Will it damage the PCM if I wire in a regular fuel pump relay. Ford wants $249 for the whole fuse block. I think that is a little excessive. Anyway, what do you think?
I would ask the mechanic if something may have been disconnected during the injector cleaning that may not have gotten fully reconnected. Everyone has their own methods of disabling the fuel pump during an injector cleaning operation. Although there are a lot of variables, it would be fairly unlikely that the two are related.
2003 Ford Expedition, the fuel light is always on and my fuel gauge does not work.(all way flat down on empty). The problem occurred when a local mechanic did a fuel injection cleaning. Right after the procedure he used to clean my fuel injectors the fuel gauge and fuel light remained on and currently is still on well after 3,000 miles or more. the truck works fine except my for my fuel gauge. I am expecting once the fuel gauge begins to function, that will solve the fuel light to turn off. any ideas? is there a fuse for the fuel gauge? do you believe it’s damage to the fuel pump/float?