Hi, thank you for responding. I will be able to start work again after 4:30P today EST.
I will give you more information from symptoms and trouble shooting.
This summer I had an issue with my fuse box. The fuel pump relay failed. I sent the fuse box off to exchange it for a furbished one.
About three weeks ago the expedition started to cut of randomly. I thought it was the fuel pump issue so I replaced the fuel pump. It continued to randomly. I also started to see some other electronic issues. The auto headlight
would not cut off, the radio would stay on after taking out the key and opening the door. I was also getting a code for the key security antenna failure (which I already replaced). I took out the fuse box and found that the PCM relay center connector had failed. This was previously repaired and is probably a previous owner fuel pump related failure. The cold solder had cracked at the previous repair probably from the heat. I did notice that the relay is always getting hot at the base before removing and opening the fuse box. At that time I believed the electrical issues was due to low voltages in the system due to the failing relay connection.
Anyway, they replaced it under warranty with another refurbished unit. I opened the fuse box and took pictures before I installed it. It appeared that this refurbished unit had the fuel pump relay replaced. The vehicle has NOT shut off on me so far. However when the fuse box was installed still observe the electrical symptoms above including the 4x4 lights flashing periodically. When the electrical issues start happening you cannot engage the 4x4, the cruise control
will not work, I have noticed that sometime the seat adjustments stop working.
So, this is why I am trying to start at the Data Link Connection to see what the readings should be and logically find the issue. Last night after I made the post I decided to focus on the violet wire at pin 3. I have read one of you precious posts that there should not be voltage on that pin (http://my.justanswer.com/question/guest/34ad906d4bed460dad4e2906e1db0ff9). I have access to ALLDATA DIY for my vehicle and understand that the violet wire goes to all the modules. I started disconnecting the easy ones to reach. I disconnected the driver and passenger seat modules. I also disconnected the c238 connector. I disconnected the PCM. The voltage remained high each time I disconnected a module.
I checked the voltage on the violet wire at the c238 connector. This voltage was on male and the female sides of the connector. This was a surprise to me.
I have also look that the cable trays at the door jams and kick plates. There is no water issues or leaks at the kick plates. The violet wire splices I could find have been in very good condition. I did find where water had gotten in to the cable tray at the left rear door. The seal where the cable goes out of the floor by the left rear door was pulled out somehow. I opened this cable and did not find and bad wires. I opened the one splice I could find by the left rear door and it was good.
I decided to remove power from the fuse box and saw a change at pin 3. The voltage started to slowly drop. It went from about 12 volts down to 0 in about 15 minutes or so. It appears that there is a something with a capacitor that is slowly dissipating. Maybe this is a clue.
This is where I am now. I put everything back together so I can drive the vehicle to work. The electrical issue are not showing now where they had been very random. The vehicle has still not cut off on me since the fuse box was replaced. The PCM relay is still getting hot near the base in the fuse box. This concerns me but I am not sure if this is normal or not. Sometimes my scan tool (Autel MD802) will not complete a full scan and it will hang up during the scan. If I only use the option to check diagnostic codes it will always complete and show results.
As a side issue I am also trying to resolve a P0401 code. I don’t think this is related the communication issues.Thanks Jack