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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23001
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I have a 2003 ford expedition. I am trying to trouble shoot

Customer Question

I have a 2003 ford expedition. I am trying to trouble shoot what I believe to be an intermittent problem with communication with the PCM. I wanted start out by verifying the correct voltage on the Data Link Connector pins. These are my results
KOEO
1. x
2. 0.49~0.61v changing
3. 10.6~11.6v changing
4. 0 - good ground
5. 0 - good ground
6. x
7. 11.36v
8. x
9. x
10. 4.38~4.59v changing
11. x
12. x
13. 0.56v
14. x
15. x
16. 12.51v
KO
1. x
2. 0
3. 11.74v
4. 0 - good ground
5. 0 - good ground
6. x
7. 0
8. x
9. x
10. 0.12v
11. x
12. x
13. 0v
14. x
15. x
16. 12.51v
Submitted: 1 month ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 1 month ago.

Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner past midnight.

  • Sorry no one has helped yet.
  • I can help with this question.
  • Reply and let me know when your able to work on this concern.
Customer: replied 1 month ago.
10/14/16
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
Expert:  Chris (aka- Moose) replied 1 month ago.

Thanks for the update. With all the new information I do not believe I can fix this remotely, I would need to do it in person. I will opt out and see if another wants to try.

Customer: replied 1 month ago.
Can you tell me more about pin 3. Should there be voltage on Pin 3? There is another violet wire on pin 10 (module programing)At Lunch I did a little more exploring and found that when I disconnected C270b fromt he junction box the voltage3 on Pin 3 dropped to a steady 9 volts with KO.
Customer: replied 1 month ago.
Over the weekend I found a friend that had a 2004 with the 5.4. I checked the DLC and found that his expedition has the same voltage as mine on pin3 as well as the other pins. At this point I am focusing my research on the SCP Bus communications with the PCM. Any ideas? I tried disconnecting the battery over night to see if I could get the scan tool (Autel MD802) to read the PCM module after the complete scan with no luck. If I only use the option to check diagnostic codes it will always complete and show results.
I also found over the weekend that I have a bad DPFE that I need to replace it. This is on order and will be installed by the end of the week.
Customer: replied 1 month ago.
I was finally able to get my scanner to communicate with the PCM. I connected to the the ABS and restraint modules first and cleared the codes.I then was able to connect tot eh PCM module and clear the PCM codes. This put things back to normal as far as I can tell. Now I have to put my car back together properly.How can I get a proper refund since I answered by own question.Thanks,

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