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.
According to my information fuse #1 in the CJB sends power to the front wiper motor, rear wiper motor, instrument cluster and low tire pressure module. The wire color code is black/pink. I would suspect the short would be at the rear wiper motor wiring where it travels through the body and into the lift gate. I could be cut into sheet metal in the roof or the lift gate door. Also the wires could be rubbed together and shorting inside the harness. I would try replacing the fuse with the lift gate door in varying positions to see if it stops blowing before dis assembly.
jeff C said…
Sparky, im having a major problem with my 03 navi. when i bought it from a dealer about a month ago the guy said the wiper fuse needed to be changed. so i did so and everything has been fine… up until about 4 days ago. i drove it for about 5 hours then five hours back. on the ride back the radie cut off for a few minuets then came back on. no problems afterthat. the next morning i got up for work and when i started the car i saw that the gauges didnt come on and the check engine light stayed on. after 15 seconds everything worked fine except the wipers. i found a blown fuse (fuse #1 10amp) which is the ACC fuse. i changed it and it blew again instantly. i turned the truck off then put the new fuse in. when i started it back up smoke came from the CJB butthe fuse did not blow. i turned the key back off. when i turned it on again the fuse didnt blow but nothing on the wiper tree worked, and the same thing happened with the gauges again. i remover the CJB and dissasembled it and found that the circuit going from the fuse #1 to the first pin was destroyed. i resouldered the circuit and reinstalled the CJB. started the truck and everything worked fine, except for the fact that i had a CHECK CHARGING SYSTEM and BAT MIL. i had the battery checked and it was infact bad so i changed it. stil had the same light. changed the alternator same problem. now it gets interesting… i took the alternator that i just took off and had it bench tested and it passed. so i know it wasnt an alternator problem to begin with. i gave up on it for the night. the next day i get up remove the CJB and remover the repair that i did on the board thinking maybe it was causing something to pull a load on the alternator since i never had this problem until i did the repair. put the CJB back in and same problem. after some tracing wires down i figured out that the VOLTAGE REGULATOR on the ALTERNATOR was not getting power from the CJB which was only allowing the alternator to put out about 5v. i removed the CJB again and re worked the soulder again to patch the break in the circuit, AGAIN! put the CJB back in and started the car up. the #1 fuse blew instantly. i cut the 12v wire going to the voltage regulator ran a 10amp inline fuse from the battery and powered it that way (which is esentialy what ford did later on in the production year to this vehicle via a fuseable link) and now the alternator is puttin out the correct voltage and i have no MIL. now the main question… the #1 ACC fuse still blows everytime i start the truck. prety much giving me the same problem i had before.when you turn the truck on windows, gauges, turn signals, hazards and radio do not work and the engine MIL stays lit. after 15 seconds the cluster comes to life the engine MIL goes off and everything works except the wipers. do you have any ideas on what could be causeing this problem or do you have an electrical schematic for this vehicle so i can see what exactly comes off of this particular circuit and try to further trouble shoot. any help would be much appreciated.
I am having the same problem. Burnt relay. I want to solder in some wires and replace the relay with a more robust unit, but I am having trouble finding information on the pin layout of those relays. It might help myself and others in the future to know this information. Thanks!
Assuming that you have a 2003 Expedition, look closely at the third picture in the post and re read the paragraph above it. You can click on the picture, to enlarge it for a better view.
I found your post and my 30 Expy is having same issue. Just cranks and does not power on. Fuel pressure is at zero, no power to inertia switch and verified voltage to the fuel pump wiring and all dont get voltage. I am pretty confident that the box needs to be replace. I am unsure about how to do the jumper wire to see if it starts up that way. Any recommendations?