I checked all fuses my lift gate wont operate with the button up at the windshield or with the remote. It will open and close manually with the lever on the door. My park assist did have a warning on the dash "check park assist" but I read on a thread here I could reset the PAM by pulling off the neg battery terminal for 20 secs. Now no warning on the dash. Also both are not listed in my system rest option on the dash. I did perform some test with my volt meter on the PAM and the sensors just seems to be a wild goose chase. Any suggestions? I do have an appointment for the dealer to scan the system. Rather not pay the $100.00 plus dollars if I could try something myself. Thanks

 

Just got back from the dealer. They said none of the modules communicated with the pcm. They said it could take them upwards of 6 hours to figure out where the problem could be at $135.00 per hour. Guess I'm back to trying to trace it myself. Anyone with some guidance is appreciated. I do have a shop manual on disc. I don't have wiring diagrams for the lift gate tho. Guess I'm off to check for power to ground. And for resistance in the communication wires.

 

I just got charged too by the way for the dealer to say, "I don't know"..."beats me"...UGH!!! Then look at me like I have three heads.

 

Typically there can be as many as 5 or 6 modules (not sure how many on your 2004) that communicate with one another over a twisted pair computer network. Some modules communicate using the SCP (Standard Corporate Protocol), some use the ISO 1941 standard, and some use the UBP (UART Based Protocol).

Your gonna need a scan tool that can read "B" (body) codes, "C" (chassis) codes, and especially "U" codes, which are network error codes, to zero in where the problem lies (as long as its not something obvious, like a damaged wire or blown fuses).

 

That's what I asked for at this dealer. One of the largest Ford Dealers in Reading, PA where I live. They told me they were going to do that before I paid for the service that they did. I guess I have to search for another dealer with that type of scan tool. Fuses checked out ok. And I did get power at the PAM when I followed the instructions via the shop manual at the wiring harness plug. I didn't even start tracing the Lift Gate problem yet. I think I will call them back tomorrow and ask if that's the scans they performed and that I asked for...if not why did I get charged for diagnostics. I have code readers and I told them it's not pulling any codes. I thought they were in the dark ages about this issue.

 

Also the service tech did say there was as many as 5 - 6 modules that were not responding to his computer. You nailed that one...Bravo Zulu !!!

 

Back at the dealer for more diagnostics and more charges. No answer yet after the second full day there. I'm getting worried and have dollar "$" signs in my eyes. I must be unique...the only one who ever experienced this issue in a Ford...Lincoln...vehicle?

 

Also they said they did do that type of scan the first time. I believe they called it a DTS scan or something. They said they check for "B" body "C" chassis and "U" error codes. They say the system still don't communicate with my vehicle.

 

4th day at the dealer. They think they found a bad wire(s) in the harness possibly from water damage. I have a wire diagram for the Park Assist. Are there any good resources for wiring diagrams for 2004 Navigator from the diagnostic plug to the other modules?

 

Did you ever found the problem? I am having the same problem, I dont have communication with 9 modules.