2007 expy major electrical problems

[giants17068]

I am going to try my best at reciting exactly what happened. Last weekend I pulled a trailer full of atvs into camp. When we got unloaded I tried to start back up to park the trailer and the truck would not crank/start. I noticed the PATS light was flashing rapidly. So i did some research and discovered that meant my key or transceiver had gone defective or bad battery, but for sure i was not getting the signal to the pcm it wanted. I called ford and they needed it towed in. I then remembered that i had remote start which should have nothing to do with either system and truck should start. Tried remote. No luck. Started messing around under dash by remote module and somewhere between wiggle and jiggle i hit the alarm circuit then remote start and the truck STARTED!! So my guess at that time was a bad battery. When i started driving in to town the wrench came on and put the truck in limp mode. So i drove to the hardware store and bought a new battery. Returned to camp and replaced battery. Still no luck. Started checking fuses and noticed every fuse to the trailer was blown except the 40A brake fuse. Replaced fuses even though they shouldn't affect the truck starting. And when I ohm out the trailer brakes they show a short, so fuse should have blown. Now when i try to start i still get the flashing PATS as well as ALL other faults coming on one at a time. The wrench, battery, over temp, abs, airbag. Oh yeah and the navigation says there is a fault. I got the truck back home and am going to start to tackle this tonight. My first thought is a short in the main harness were the trailer brake transducer wires run beside the data connector to the pcm. Sorry for being so long winded but I am really looking for some assistance and wanted to be as thorough as possible. Thanks Dan

 

[giants17068]

Pcm

Could it be that my PCM is bad. I could not communicate with it via an actron cp9385 scanner. I read somewhere about the lighter fuse but that works. I have never actually seen one go bad. The scanner works on my 2004 chevy 2500hd truck so it is not the scanner.

 

[mrford60]

when you are checking fuses look and see if any of the pcm fuses are blown and check if the test port (obd2 plug) fuse is blown.

 

[giants17068]

I have checked every fuse related to the pcm and I tested for supply voltage at the pcm as well as at the data link connector. Everything checks out. Thanks for the thoughts though. That is really what I am looking for is some guidance as to where to start. I have the ford wiring diagrams book for my truck and a test light/ multi-meter. As well as a scan tool just can not find reason.

 

[giants17068]

fixed

Okay well just to update. I found my problem using the ford service manuals and a meter. If you do a search you can buy the rights to every service manual for your particular ford for use of a month. All for the very low price of 19.95. Believe me this will be the best 20 dollars you ever spend. It had step by step instructions on what to do if you lose communication with a scan tool as well as every other electrical symptoms you may experience. So if you are willing to put some effort in and can read the same material the dealer mechanic is going to read, you can save yourself about a hundred dollars an hour. So anyway it ended up being a short in my transmission harness that was shorting my hs can to ground causing all of my communication network to fail. Which of course the manual told you which pins to check in the DLC and what the readings should be. So if anyone needs some help in future don't be afraid to pm me I will be more then willing to help.

 

[mrford60]

I am glad you found the problem. factory manuals are very helpful. sometimes you can find the whole books on ebay at a good price.