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  #1  
Old May 20th, 2019, 21:12
4x4JeePmaNthINg's Avatar
4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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need clarity P1391, heres what ive done thus far

Quote:
Originally Posted by jtec View Post
maybe your scanner is limited, there is a sync function for checking CMP to CKP correlation. basically looking for timing, Cam TDC to Crank TDC, think timing marks.

Anyway here is the troubleshoot list for this code...

I went back through today and test continuity point to point from all harness supply,ground,signal to pcm and ground to body/block, just a few locations to make sure grounding was good.

-I have 5v supply with key on and running
-continuity from sensor harness to pcm plug is good
-continuity from ground harness to ground battery,block, and strap just for the hey of it
-wiggled the crap out of wiring from cmps to ckps to pcm and grounds with no change.
-ohm tested ckps again for the sake of doing so while the vechile was warmed up, all good here to.

idle definitely fluctuate a little and has noticeable misses but when driving it is smooth

- distributor assembly only replaced, just to make sure the gear wasnt causing the pulse ring to wander, no change here
- ignition coil was replaced as well, just in case, Napa echlin, also no change


for the cam to crank sync, is this simply monitored by the lab scope and if one is off thats the culprit? or is there any other relationship between this synchronization that needs to be checked into?

this issue existed before and after an engine swap, the replaced parts above were after the swap.


im trying to exhaust all my options with in financial reason to NOT take this to a shop. I paid damn good money for the engine and really dont want to dump diagnostic coin for something that could be tricky to figure out.
i use loc tite on all flexplate bolts, ckp was removed before pulling old engine as to not damage it.


what would you all do next, what else would a shop be doing that I havent?????
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  #2  
Old May 20th, 2019, 21:43
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: need clarity P1391, heres what ive done thus far

Naxja we really gotta fix this no edit thing, literally the only forum that doesnt let this happen.

Sorry I couldnt edit the first post folks.


The scanner I used was blue driver, in which i did not get a sync function of freeze frame function to work.

this is the second time verifying ground and voltage supply, i did not hook the analog up to signal because it wont give me anything i dont already know without a scope.

Ive visually inspected the harness three times for breaks or corrosion
I do not have a 4 prong scope to see sync of ckp/cmps signal.

ide also like to add all bolts were torqued and loc tite used when bolting everything up, ckp was removed before swap as to not damage it.

all sensors are mopar

battery disconnect reset the CEL is back every second start without fail, airbaig light intermittent- unrelated i assume.

is there anything else i can use to pinpoint what is going on if ive done all possible tests with a multimeter?
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  #3  
Old May 21st, 2019, 08:56
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lazyxj lazyxj is offline
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Re: need clarity P1391, heres what ive done thus far

Quote:
Originally Posted by 4x4JeePmaNthINg View Post
Naxja we really gotta fix this no edit thing, literally the only forum that doesn't let this happen.
Sorry I couldn't edit the first post folks.
There is a fix for your editing problem, pay up and join .
Members can edit their postings, freeloaders can't
Do you think the forum cost nothing to run?
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  #4  
Old May 21st, 2019, 12:06
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: need clarity P1391, heres what ive done thus far

Certainly not sir, but an edit function is a basic rudimentary function. It aids in keeping posts clean and the option to reword previous posts if needed. All together ide think it helps the forum look a little neater (more processional) even for small tweaks, but hey I didn't choose this.

Anyways, whatcha all think, am I dead stuck in lab scope territory?
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  #5  
Old May 21st, 2019, 18:28
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Re: need clarity P1391, heres what ive done thus far

Quote:
Originally Posted by lazyxj View Post
There is a fix for your editing problem, pay up and join .
Members can edit their postings, freeloaders can't
Do you think the forum cost nothing to run?
That there (correct me if you feel I'm putting intentions behind your words) "snobbish attitude" is the reason I stayed "Black" while posting helpful information, got involved with people, and attended local events.

BTW, the entire time I was a USER, I could edit my posts for 20 minutes after making them.

Matt, I won't lie, I never did read that manual you posted.

My education that was specific to industrial sensors, actuators, and controllers (ladder logic), makes me wonder if the OBDII software defaults the CPS to be correct, even if it fails to register on a consistent basis.

Years ago, a Colorado Chapter member posted a picture of his MOPAR crank sensor. He noted the addition of a round "sticker" that fell out of the box. The instructions said to stick the little round sticker on the end of the new Crank Sensor, loosely install the sensor, push it against the flywheel/flexplate, and tighten the sensor bolts. On startup, the sticker would be stripped from the sensor, providing the correct air gap between the sensor and flywheel/flexplate.

Without that sticker, how does one set the air gap?
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  #6  
Old May 22nd, 2019, 03:42
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Re: need clarity P1391, heres what ive done thus far

Lol all for the better Mike, while it contains much, it is missing plenty.

I have read that this sticker did not apply to my year, the Mopar part I replaced with came in a plastic bag from the dealer. Two bolts on the bell should put it dead on i guess, there isnt any room for adjustment, Idk if theres truth to this. Both sensors were quite expensive as they are genuine Mopar parts, nothing new to those here. It is for this reason and that the originals lasted almost 190000 miles, that I am hesitant to just slap new ones in.

You wouldn't think with as many questions as I've got that I read on here, but typical to forums is the missing link of info in between the common knowledge many for get is unknown.


As much as i Hate it!!!! I guess this is just one issue ive got to suck it up and take this thing in, or buy a scope for thousands.


If anyone thinks of something to try I'm happy to run through it and post back, until then I'm gonna bite my teeth and call some fart to take my money. Loooathing this lol
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  #7  
Old May 22nd, 2019, 04:06
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Re: need clarity P1391, heres what ive done thus far

From the tone and content of your postings one might suppose that so far there has not been enough research done on the topic.

If all the basic P1391 causes have been diagnosed and eliminated, that leaves the Cam Sensor Synchronization as the remaining primary suspect. Have you read the concurrent P1391 thread started by RCP Phx ? Many threads say that all you need is toothpick. Cell phone Oscilloscope Apps don't cost hundreds of dollars, and a dedicated digital handheld scope is $75.
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Last edited by Tim_MN; May 24th, 2019 at 18:24.
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  #8  
Old May 22nd, 2019, 04:58
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Re: need clarity P1391, heres what ive done thus far

Quote:
Originally Posted by Tim_MN View Post
From the tone and content of your postings open might suppose that so far there has not been enough research done on the topic.

If all the basic P1391 causes have been diagnosed and eliminated, that leaves the Cam Sensor Synchronization as the remaining primary suspect. Have you read the concurrent P1391 thread started by RCP Phx ? Many threads say that all you need is toothpick. Cell phone Oscilloscope Apps don't cost hundreds of dollars, and a dedicated digital handheld scope is $75.
tim, respectfully I do ask you to elaborate? I have followed, read, and read, and read, and read some more, and begged local help, and read. Lol, I know im a pain in the butt at this point, but it hasnt been without effort for trying to do this myself and correctly.

Now I have read 40+ threads, many with your much appreciated help on some.

correct me if i Missed something, but I have:

.tested grounds 2x
.tested signal 2x
.tested supply2x
.tested pcm, ground and sensors harness continuity 2x
. ohm tested ckp and analog test, flex plate aligned to verify 5v recognition
. analog test of cam postion sensor
~ all done key off, key on, running and wiggling the crap out of wiring
.check pulse ring and cmp visually
.replaced and reinstalled new distributor, for the 4th distributor install on this engine ( 3 times stock, once new) and it has not changed, FSM install followed exactly. TDC achieved, wooden dowel 4.0 aligned, It does not go in correctly otherwise! if it could, im the guy the could have and I Have Checked lol 4x
.visual wiring inspection
.flex plate visually inspected
.wiring visually inspected 3x

- cam crank sync check- missing diagnosis for lack of tooling.

if a cell scope exists,im new to this news and you bet im looking it up, But dont I need 4 probe scope for diagnosis of cmp,ckp synchronization?


If i missed it researching I have spent over a year of reading on this thing, i have read toothpicks and O scopes.


the scope is all im firing in my lil brain as something thatll show a relationship that cant be steadily seen with a meter.

i havent tried a Hammer yet? but it is tempting..........hmmmm
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  #9  
Old June 12th, 2019, 12:15
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Re: need clarity P1391, heres what ive done thus far

To the shop it went for a diagnostic.

Car diagnostic run, p1391, 99% the pcm is throwing the code for no reason.
Cam and crank sync up, scope is clean. Signal is getting to the PCM.

They suggest flashing/update it at the dealer maybe before looking for replacement.

Now what do I need to be concerned about as far as PCM goes?
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