I have a 2005 FX4 that has been sitting for 3 years. The previous owner went out of town for an extended period of time and when he returned squirrels had taken up residence under the hood. They chewed on one of the harnesses near the pcm. He took it to a shop (not a dealership) and they made repairs to those wires. He drove the truck without issue for a while and one day it wouldn't start so he parked it and bought a new truck. I have replaced the pcm, programmed the new keys to it, checked the repaired wiring and inspected the fuses and relay associated with the pcm. The cluster lights all work but I have no crank, no communication with the scanner and cannot detect the fuel pump coming on. Do you guys have any ideas on where I should go from here with it? T.I.A.

 

My best bet is your going to have to get the wiring diagrams for your model year and test for power distribution and ground circuits involved in the the issues. There are multiple fuses involved in some circuits that may not be listed in the owners manual. Some wiring diagrams also vary by engine size.
Check fuse 5 - 7.5amp and fuse 28 - 5amp in the central junction box. They're involved in the pats system.

 

Ignore the PATS system for now, it is a secondary symptom. Start with getting the PCM to power up and properly initialize everything else.

How could you possibly have "replaced the pcm, programmed the new keys to it" when the scanner cannot communicate with the PCM?

 

Was it running when pcm replaced and afterwards. Not a successful change out if it wasn't running - you would have had to have comm to do it .

 

The pcm was ordered from flagship1 along with the set of keys. The PCM was programmed using the trucks VIN# and is supposed to be plug and play. Does that make more sense?
I appreciate all the help fellas.

 

Well i would check all fuses in passenger kick area . Check grounds in same area there's a bunch that get corroded right there .You may not be getting pcm powered up . You are going to have to use test light and diagrams to see if its getting to all the places it needs to . The pcm has more than one feed . You need to get that diagnostic port running but it won't work if pcm not powered up . Pcm will supply ground to satrt relay when its satisfied . The positive to start relay comes from ign switch thru trans switch neut/park under truck ..


This won't help until you get pcm fired up and diag port working . Because even if it cranks no ground pulses will come from pcm to injectors or cops .The grounds and fuses are a good place to start . Rusty grounds don't work . Make sure you have the plugs on pcm in the right place .

 

Update: upon inspection of the harness repairs made behind the battery tray I found a ground wire that had been missed. I repaired the wire and now have the pcm powered up and communications with my scanner but now have a rapidly flashing security light and still no crank/ no start and no fuel pump.

 

Also, I have hooked up the original pcm and tried everything with the old key and am getting identical results.

 

And what does the scanner say when you pull codes or run a PCM Quick Test?

You will continue to have the "no crank/no start" condition until ALL prerequisites, including PATS, are met.

The fast-flashing THEFT light indicates PATS is not happy. Could be incorrect or incomplete PATS programming, could be a missing prerequisite. The fuel pump priming cycle is not dependent on PATS, but it does have a successful PCM boot-up as a prerequisite, along with external circuitry.

 

The scanner shows no codes and I'm sure that's due to it being a new pcm and the truck not running the last 3 years.

 

If it had failed to start due to a PATS concern, THAT event should have set a fault code.

Are you using a scan tool that is a simple "code reader" or what?

 

I may be able to download more on it but as bought i think its a pretty simple one.

 

Progress- but I don't see why old pcm and key shouldn't work . How many old keys do you have and make sure its an electronic key not just a mechanical key . try both old keys . you have got to get that pats light normal . How exactly did you program new keys without a live pcm . Have all keys in truck near ignition sw to see if any of them will make it happy . Some smarter guys will come up with a better answer/ guys who have fought this same area . Check for more chewed wires also . Make sure they were soldered in when spliced . I doubt your old pcm was bad . I don't really know the pats system all that well .
I do know how to get start relay picked up to make it crank . All it should need is the ground signal from pcm side .

 

Do you have power to pin 86 of the starter relay with key in start position to verify the DTR sensor is working in park and/or neutral as per the wiring diagram?

 

You can supply ground to pcm side of start relay to see if she will crank . Its up to you if you use a fused jumper in case you make a mistake a 3-5 Amp fuse will be plenty . I do recommend that ,it minimizes damage if you put it to the wrong place .clips on the end allow you to put a bent paper clip in it to get it to a small area .A clean shiny paper clip makes a good probe .