Hey all, I apologize in advance this may be long winded. Truck is a 04 late build.
So truck was starting fine, go out to move it and turns into a no start. I scanned for codes and found P0341 P0401 P0407 P0488 P0683. hmmm, ficm doesn't move from 48v, logic and power showing 12v but sync showing 0 and so was cam/crank sync when cranking. rpms showing strong and the cam sensor and pigtail was an oily mess from a chewed out sensor Oring so I replaced both. My egr is deleted with throttle plate removed so the 401 and 488 is usually there. I did the head gaskets last year along with stand pipes and dummy plugs and don't think that this is a no start on the oil side of things. icp is .24 koeo, ipr 14.8% and when cranking ipr is in the 40% range with icp around 1200psi (gauge on dash also rises). Batts are strong and I have a good cranking rpm. I keyed on a handful of times and the gpcm code kept reappearing so I checked the wiring and plugs (had the loom completely apart and ohmed the harness from the ecu plug to the gpcm plugs and checked them to ground). Knowing the gpcm rarely fails some Google Foo turned up that the p0683 can only be the gpcm, wiring, or ecu so I replaced the gpcm and the code hasn't come back (I also ohmed all the glow plugs from the harness connections and all came in around 1.5-2.0 ohms). Now comes the head scratcher, if I crank it like it's nobody's business it may actually start (like after 8 seconds) and runs like a champ! Sometimes it throws a P2614 however I think that has to do more from the excessive cranking when it doesn't start. I ohmed the cam sensor from ecu plug and got 825 ohms and crank sensor is 340 ohms. I don't have a lab scope so I can't watch the signal but I am using auto enginuity but not sure if it's capable of reading the signal. So after the truck starts the sync will switch to 1 and will run and drive strong and after it warms up I can shut it off and come back 5-10 mins later and it will fire up almost like normal (maybe an extra half second but nothing like that first start up). The only code that is coming up now regularly is a P0470 and I am going to throw a new ebp sensor at it because koeo my baro and map are 14.7 but ebp is 17ish however I don't think this is the cause of my no sync when cold. An interesting note is after the first long crank/start when it does eventually fire it lights off like a hot damn. Doesn't stuggle to start or puff black while cranking, it's like some body snapped their fingers and all was good. I've had the ficm out and made sure the plugs were seated but I'm starting to doubt that the no sync has anything to do with my harness because it should be a hard start even after warmed up. Where do I go from here fellas, it's really stumping me. Do I have one of the rare ecu failures? Physically pull glow plugs and put them across 12V's (although this wouldn't explain my no sync...plus I'm not throwing any gp codes). Is my auto enginuity having a hard time reading the sync and it's really there but not showing me (unlikely because I also have torque pro with the sync pid and it's showing me the same). I'll leave it at that for now, any help is thanked in advance! I'd rather solve this in my driveway than pay a shop.

 

You need CAM and CRANK to be a 1 to get FICM to be a 1... IF THEY DON'T and stay a 0, it won't start.

MAP 14.7
BARO 14.7
EBP 14.7
all are good, until the truck starts, then MAP and EBP are about 17.0 or so, that's good.

ICP .18-.24
IPR 14.7
Both good, ICP 1200 and IPR 40% cranking good.

You don't need glow plugs if the temps are warm enough. It will run rough and then once warm, smooth out when the cylinder fires a couple times.

YOU NEED SYNC...

 

Thanks for taking the time Watson. I understand that there is ficm sync and there is pcm sync/sync/cmp ckp sync and you won't get ficm sync till the other one is met first. I've heard the other terms for pcm sync listed above but I'm wondering is it the same sync but scanners just label them with different name? My only 2 choices on auto enginuity is the ficm sync and cmp ckp sync. When the truck is up and running my cmp ckp sync toggles between 1 and 0 however I've found plenty of threads about other trucks that are running fine doing the same, and I think it was bismic that said in another post that this may be normal because every time the cam pin sweeps the sensor it breaks the magnetic field.

Also my ebp sensor is at 17psi koeo and it shows while driving, unplugged it sounds like I'm straight piped at idle so I will be throwing a new sensor at it.

So I'm left wondering where I should go from here because it seems that it could only be either the sensors, wiring, pcm, or ficm? Why only a bear to start when cold and doesn't do it once it's warmed up? Although more of a 7.3 issue I have heard where the fuel heater starts to short and robs the pcm of power because they're on the same fuse.

 

Might be the FICM... try warming it with a hair dryer. Once it's warmed by engine heat, that could be an issue if you have a non-conductive flash.

Could be a cmp ckp sensor, not sure why it would go from a 1 to a 0 and I would think it sweeps fast enough to not really change the sign to a more negative value causing a no start or a long start. Try unplugging them and re-seating the connector, could be that they are dirty at the surface and it's not making good contact, maybe a shot of connector cleaner. They make some spray stuff you can pick up and shoot at it while its in you hand I've heard works pretty well.

 

Reiterating what Watson just said, symptoms sound like possible poor continuity. The products I reccomend are Deoxit 5 and Deoxit Shield. Since it's the easiest to access and most common to fail,start with un-plugging camps,clean and reconnect. It's not much more trouble and expense to replace cmps but plug take's some time to replace right. Dealer doesn't sale camps pigtail but it's same as egr valve. I clean ever thing I unplug while maintaining and repairing. I also normally apply di-electric grease on plug body and boot but not on pins to prevent moisture intrusion.