Hello to all. Have searched for this topic prior to posting. new 408 engine. PCM is flashed, etc. I keep getting the 1391 code for inter. loss of crank & cam sensor. Both sensors are new yesterday. Further, the fuel synch was set with a scanner. Still throwing the 1391 code. Truck exhibits all symptoms of this code. I checked the pigtails both 5.14V coming in to each sensors with no fluctuations.

So I guess my question is - is there a "synch sensor" screen or function that I may have missed on this that somehow makes both new sensors slave to the PCM? I have heard of this and that it is different than just "set fuel synch" screen.

I struggle with that a bit in that in previous trucks we have swapped out crank or cams sensors as needed and never had the 1391 come back.

Lastly, I have double checked the timing and it's dead on. And, the crank wire harness is not crimped or cut either. Anything you can share is sincerely appreciated.

 

what is a 408 stroker is a 318 base or a 360?

 

maybe a bad sensor.

 

318 or 360, you can make the 408 stroker out of either one due to the same bare block. i know this because rm-indy has the 360 block based 408 stroker and i will be building mine out of a 318. but as of the problem, i would say to try to clear the code. undo the battery, and then unplug the pcm for about two min. then reverse steps, pcm, then batery, and see if that fixs it. its the only thing i can give here.

the reason i say this is you may have changed the sensor but the computer hs that bad part sotred in the comp. so by doing this, it will reset everything... hope this works for ya

 

Is this a B&G flashed pcm? Ive heard of a few guys getting weird codes on occassion. I fired up my 408 on one and couldnt run it cause I couldnt set the fuel sync. All it had in it was fuel/timing maps and the trans diagnostics. Motor diagnostics were wiped for some reason.
Have a spare stock pcm just to see if it throws same codes? Anything else I would suggest you have checked. Im no expert especially when it comes to electrical related issues. Struggle with them myself tbh.

Bdodge60
408 stroke requires a 360 block
390 stroke is max for the 318 block

meanwhitemopar is confused!! Never said anything in my reply to his pm to imply 318 can be stroked to 408

 

Mean White & RM - thanks, both great suggestions.

Here is what we think happened. Initially after replacing the crank sensor, we did the "sync signal" function - to no avail. Subsequently, replaced the cam sensor and did the "sync signal" function again - and still 1391 came back. And we played with it going up to +6 down to -2, etc. After checking everything again even the voltage coming in, we reset the PCM, and the code cleared. Shut it off, restarted it - code came back. Reset it a third or fourth time - code cleared and never came back. So we are atributing it simply to the code hanging up in the PCM - because we couldn't come up with anything else!

Truck runs great, the 408 is really what that heavy AWD Durango needed.

 

ok then, my fault on the me being stupid. i hought they were the same block though? just different strokes to give the bigger size? i was previously mislead! and now that 390 is the 6.4 right? what is the 408?

and glad you had the problem fixed,

 

6.6885245. I'd say it would be called a 6.7.

 

ok, thats lot of motor... holy crap, how much power would a 390 make compared to the 408, cause i wont have the 408 now. i will have the 390. i will probably have the good head, all the roller rockers, roller lifters, and an ok compression. what kind of power should that make?

 

Congrats on figuring it out!!


Meanwhitemopar
390ci maybe in the 300-370rwhp range depending on cam, heads & level of port work. A buddy building one, hasnt finished his yet. His prior 349 stroker (5.7 lol) put down 1rwhp more than my mild 360(stk hds) did years ago. Think he got 271/310rw with that.