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.
Back to the original post…I just need to find out where I can buy the CJB. We took off the old one and yes the board is burnt up. and yes ford does need to recall these, so many people are having troubles. We need to replace it but where do I get it? Sorry I’ve been all over the net looking and cant find anything. Is this an item from the dealer or am I using the wrong name for it. Any help would be appreciated. I may not be the only one who needs this info. Thanks again.
If your gas tank is very low in fuel(only a couple of gallons left in the tank) you do run the risk of sucking some air. Fuel gauge systems are designed to compensate for this by reading empty while there is still adequate fuel in the tank to prevent this. If there is a noticeable engine performance problem when the fuel reading is at or below 1/4 of a tank, it would suggest that there is a plumbing problem (leaking hose) inside the gas tank. It is best to always keep your gas tank above half a tank. A quarter of a tank minimum. The reason is that the fuel is also a coolant for the fuel pump. A hotter pump draws more current and causes some of the problems we have been discussing. If your vehicle has a replaceable external fuel filter it should be changed at 20,000 to 30,000 mile intervals. Restricted fuel filters cause fuel pumps to work harder and draw more current.
Greetings Sparky and forum friends: A couple of months ago my vehicle experienced the condition list here. I removed the fuse box panel. Took it apart and found it was the relay solder joint and the relay was slightly melted, but not to the point it was unusable. Since it was not in my budget to replace the box at that time and could not wait for a new relay, I had to put the box back together – whew what a task, and prayer was utilized with putting it back together because I didn’t know the relay contacts held some of the components together.
Anyway, I got it reassembled and I was just going to jumper it. However, I remember after I found the “cold” solder joint, I fiddled with it a little bit and did not bother to re-solder it at that time. To my surprise, I must have moved it enough to cause the solder joint to make contact with the circuit board runs. I started the truck and drove it for the past couple of months with no problem. The high current condition, I believe is caused by running the vehicle with low fuel. As long as I kept a quarter tank or more, I did not have a problem. The past few days I ran the truck on low fuel, where the alarm came on. This morning when I went out to start it, the joint had most plausibly heated up enough to expand to the extent that once it cooled, it was no longer in contact with the circuit board runs. So, if you’re having this issue, I would presume one possible cause of the high current condition is caused by low fuel, thereby, causing the pump to work harder, therefore demanding more current. The reason I think the pump works harder, depending on how the vehicle is driven, there may be times when the pump is “sucking a little air”. I can’t say for sure, but it is a great suspicion. If someone who knows how it could cause the pump to draw more current, please confirm. Thanks. This forum, as I anonymously said before, is priceless. Just think of all the people who have benefitted. Thanks again.
Hi RD Summ,
I doubt that the fuse box is contributing to a poor run // misfire condition. I would suggest having codes and data inspected to determine the cause of the problem. In particular look at Mode 6, CID 53.
The Expedition fuse box in this article is plug and play with no programming needed. I cannot say that your Navigator is using the same part. Because of later year and higher trim level it may have a electronic module built into it that requires programming.