Dodge truck running issue, P1391 trouble code

[fabiodriven]

Looking for help with a P1391 code on a two wheel drive 1999 Ram 1500 five speed with a 318. If you have not experienced this issue before personally, it's unlikely you'll be able to help. Please forward or share this to any people/groups who may have experience with this particular issue in a Dodge truck.

I bought this truck for very short money in the intent of driving through the winter as to keep the salt off my Ford. I expected it would need a little work which is fine, but it's about to turn into a huge loss of time and money for me. This is a last ditch effort at finding help before I have to get rid of it and take a loss that I'd prefer to avoid.

The day I brought the truck home it ran fine. It had the check engine light on which was a surprise to the previous owner, however it had been sitting for quite a while and seemed acceptable to me because the truck ran perfect. On the half hour ride home it ran fine and the check engine light didn't come back on after I stopped on the way home and shut the truck off then continued along my way. It subsequently ran fine for a few weeks while I moved it around the yard. One day it started running poorly and the check engine light came on. I Googled the P1391 code and came up with an unpleasant surprise. Apparently these trucks are known for this. The code is a blanket code which denotes a problem with either the cam or crank sensors, but on a basic scanner it will not say which sensor is the problem. I started by replacing the cam sensor and that seemed to fix the issue. I parked the truck for another week and when I went to move it again I was very disappointed to see the problem had returned and the check engine light was indeed on again. I then replaced the crank sensor which did not fix the problem but did make the truck run a little different than it was, but it still runs bad. Before the crank sensor change, the truck ran rough at idle but would run perfect when on the throttle. After the new crank sensor was installed, it ran much better at idle but runs awful when you get on the throttle.

This is not uncommon with these trucks and my research has netted me zero cut-and-dry repairs in order to fix this. It's suggested to chase wires and check grounds as well as connections at all sensors and PCM connections. That's what I have been doing but with no improvements.

I don't know what else to do but get rid of the truck, and I'd much rather fix it than send it along and lose hundreds of dollars for nothing. I put four tires on it, a battery, crank and cam sensors, fixed a clutch pedal issue, and changed the transmission fluid. I stand to lose a lot more money than I'd like to here as well as a good amount of time.

As I said, I am looking for someone who might have experience with this particular issue on these particular trucks, not guesses. The truck doesn't need a tune up, this problem turns on and off like a light switch and it runs perfect when it's running the way it's supposed to. The timing chain isn't stretched, there is gas in it, etc...

Please help me if you can.

[Shep1970]

Went through this same thing on a 2001 dodge dakota but with a 287 not a 318. It ended up being the iac valve- idle air control valve. I bought a new one but first i wanted to try to clean the old one, i also sprayed carb cleaner in the port. I installed it solved my problem.
The valve moves slightly in and out but it gets all carboned up.
Fixed my issue quickly but as i remember had to do it yearly for the same problem.

So it could be a free fix?
Figured i'd share since the two models probably have similar carbs.

Shep

[fabiodriven]

I don't know that an IAC can cause a cam/crank sensor code but it's definitely worth a shot. Thank you Shep.

[big specht]

Is there a relearn procedure ? Some vehicles have that. I'm just spitballing

[barnett468]

.
From my fading memory, I'm pretty sure your truck has an OBD II computer system, and on at least some (if not all) of the vehicles with this system you can have a diagnostic test done. This test is done with a more expensive test unit then just a code reader and it typically tells you exactly what the problem is instead of giving just just a general description like "something in your engine is fkd up", unfortunately many people on the forums are not aware of this test so you may not easily find info on it, however, if you call a dealership or a few different shops they should be able to tell you if it is possible to do this more elaborate test on your model with your particular code problem even if it is intermittent because that info is stored in the computer even if the light is not flashing but I don't remember if disconnecting the battery erases the memory in that particular section of the computer.

You might also give the place below a ring and ask to talk directly to the tech. This is where I am going to get a computer for my durango at and he sounds like he knows his stuff and may be familiar with the problem because they do a lot of computers there including some for auto parts stores.

http://car-computers.com/


I am currently trying to fix a problem on a 2009 durago with a hemi that no one has ever heard of before including people that repair the engine control computers so I feel your pain, lol.



PREVIOUS KAWASAKI INTERNATIONAL R & D PROJECT ENGINEER AND ATV DEPARTMENT SUPERVISOR AND THE ONLY PERSON ON 3WW WITHOUT AN EDIT BUTTON OR A STAR :Bounce

[fabiodriven]

Is there a relearn procedure ? Some vehicles have that. I'm just spitballing

Actually, Garry Crum informed me that the cam and crank sensors must be synced after replacement, so there's that. My buddy is coming by this week with a Snap-on scan tool to get some more information and sync the sensors.

Thanks very much for the post to Barnett as well. This should answer your post also.

[wonderboy]

Hey fabio,

I wanted to pull up as much useful info from the service manual as possible, but there isn't a lot of good stuff.

A few comments: I found mention of the synch procedure you mentioned. It really only applies if you've pulled the distributor out of the engine, and lets you get it back in the engine and aligned. An interesting thing that I noted from reading the manual is that the timing for the engine is NOT controlled by the distributor at all. As long as the distributor is rotated within a certain acceptable range, the PCM controls all timing. The synch procedure will simply make sure the distributor is in an acceptable window. With that said, I'm guessing that if the distributor is NOT in an acceptable window, then it probably wouldn't run well.

Here is what they say about the ignition timing:


CAUTION: Base ignition timing is not adjustable on any engine. Distributors do not have built in centrifugal or vacuum assisted advance. Base ignition timing and timing advance are controlled by the Powertrain Control Module (PCM) Because a conventional timing light can not be used to adjust distributor position after installation, note position of distributor before removal.

Here is the cut and paste from the manual (note DRB is the corporate scan tool of the day, I'm guessing the Snapon tool provides this same information):


CHECKING DISTRIBUTOR POSITION

To verify correct distributor rotational position, the DRB scan tool must be used.

WARNING: WHEN PERFORMING THE FOLLOWING TEST, THE ENGINE WILL BE RUNNING. BE CAREFUL NOT TO STAND IN LINE WITH THE FAN BLADES OR FAN BELT. DO NOT WEAR LOOSE CLOTHING.
1.Connect DRB scan tool to data link connector. The data link connector is located in passenger compartment, below and to left of steering column.
2.Gain access to SET SYNC screen on DRB.
3.Follow directions on DRB screen and start engine. Bring to operating temperature (engine must be in "closed loop" mode)
4.With engine running at idle speed , the words IN RANGE should appear on screen along with 0°. This indicates correct distributor position.
5.If a plus (+) or a minus (-) is displayed next to degree number, and/or the degree displayed is not zero, loosen but do not remove distributor holddown clamp bolt. Rotate distributor until IN RANGE appears on screen. Continue to rotate distributor until achieving as close to 0° as possible. After adjustment, tighten clamp bolt to 22.5 N·m (200 in. lbs.) torque.

The degree scale on SET SYNC screen of DRB is referring to fuel synchronization only. It is not referring to ignition timing. Because of this, do not attempt to adjust ignition timing using this method. Rotating distributor will have no effect on ignition timing. All ignition timing values are controlled by powertrain control module (PCM)

After testing, install air cleaner assembly.

[wonderboy]

The manual is extremely brief when discussing this fault:


Symptom:
P-1391 INTERMITTENT LOSS OF CMP OR CKP
When Monitored: Engine running or cranking.
Set Condition: When the failure counter reaches 20 for 2 consecutive trips.

POSSIBLE CAUSES
RECORDED LAB SCOPE PATTERN NOT IRREGULAR
WIRING AND CONNECTORS OBSERVABLE DEFECT
SENSOR DEFECTIVE


A lot of the diagnostic procedure involves looking at the signals from the cam and crank sensors. Without a tool that offers an oscilloscope type functionality (freeze frame view, etc) this will be very hard (impossible).

Other things to do are what you already know (cut and paste from manual):

Carefully check the Wiring Harness for any signs of external damage.
Carefully check the Connectors on the Sensors and the PCM.
Are there any problems with the Harness that can be seen?

One thing that I know can happen is that the terminals in the connector itself can become spread. In other words, the wiring harness female terminal gets too loose and doesn't make a reliable connection with the sensor male terminals. One way to inspect for this is to get your old sensor and hack out one of the male electrical terminals. You need to get as much of the terminal as possible. Then you can hold that terminal with your fingertips and carefully insert it into each of the harness side connectors cavities. You are checking to see how much physical resistance you feel. You need to make sure there is some friction as you insert the terminal. The only real fix is to replace the connector by splicing on a new one. If you go down this road and think you have a bad connector, PM me.

Hope you can figure this out!

[wonderboy]

Schematic just in case you need it:247484

[briano]

Make sure the Throttle Position Sensor is within range. The TPS can do goofy things to a Dodge. Also, they need a good battery.

[fabiodriven]

Wonderboy thank you so much for all of that information, seriously. It's always good to understand how these systems work and that just explained a lot. I'm sure that will be of help.

Briano I don't understand why the TPS wouldn't just trigger a TPS code, but I don't doubt what you're saying at all. With the amount of causes I've seen for this issue, a TPS issue wouldn't surprise me at all if it were the culprit. I just put a really good used battery in it. It cranks over really fast, very big battery for such a small truck.

[fabiodriven]

Diagnostic computer was here today and this is what we found; truck was running awful when we first started it, worst it has run yet, but the check engine light would not come on. I was extremely frustrated because it had been on for weeks and I was beginning to worry it wouldn't come back on. After a half hour or so, it did finally illuminate. p1391 code obviously. After running the truck for a long time it eventually started running better and better until it was running perfect. We cleared the code, ran it for a while, and the light stayed out. In viewing the parameters in real time, they fluctuate like crazy. It doesn't look right to me but I don't know what right is supposed to look like. I'm thinking crank sensor replacement with an OEM unit will fix it but I'm still guessing really.

https://youtu.be/P-PKnsVDXRk


Sent from my iPhone using Tapatalk

[fabiodriven]

I'm going to go ahead and keep this updated in case it can help someone in the future.

The p1391 code in these Dodges is a very common code that can have a multitude of causes. Most commonly, the issue has to do with the crank or cam sensors or the wiring to either of those two, which is known to corrode and fail. Other known causes are PCM issues, PCM connectivity issues at the plug, dirty reluctor pickup for the cam sensor, metal debris stuck to the crank sensor (which is magnetic), damaged crank sensor pickup on the flywheel, and even a faulty ignition coil. Learning about all these causes is initially enough to make a mechanic throw their arms up in confusion, especially when the vehicle is supposed to be low cost and temporary.

I had some friends help me with diagnostics via the Bookface and I am grateful my other buddy was able to bring his Snap-on scan tool by. Using a multimeter, I was able to test for the 5 volts required each for the cam sensor and crank sensors. Voltage was fine. I then checked each for a good ground by checking for resistance in Ohms. Both supply voltage from the truck as well as ground on the truck harness side are good, which makes it likely (but not definite) that one of the sensors is the problem. Based on the readout from the scan tool, the crank sensor appears more likely to be the issue. The readout for it seems very erratic, however I don't know how that reading is supposed to look. Others agreed with me it looks odd, so that's what I'm going with.

Anyone who spins a wrench, especially on sub-par Dodge vehicles, will tell you the importance of using OEM sensors in these trucks. This experience may add yet another bolstering point to the fuss so commonly heard about using aftermarket sensors in these turds. I have a feeling the cam sensor will be fine, but I think after I install a brand new OEM crank sensor the truck will run right again. I installed an aftermarket crank sensor and that did change how the truck ran, but it it didn't run any better, it just broke up at a different RPM than it used to.

I decided to remove the aftermarket crank sensor after I'd installed it to put the used factory sensor back in before diagnosis with the scan tool. Upon removal of the aftermarket crank sensor it was clear that the sensor was in contact with the flywheel physically. This sensor was an eBay sensor, but was billed as "a quality aftermarket unit" and the description addressed the exact concerns I had in mind as far as fitment and operation. It performed exactly as I'd suspected, assuming the OEM part fixes the problem. It didn't fit right and the truck didn't run right, and I'd even have to wonder if it damaged any of the pickup on the flywheel or the flywheel itself. I doubt it did but you never know. Advance wanted $90 for a sensor which they would have had to order. I already knew nobody used aftermarket crank sensors and the fact that they didn't have the part on the shelf told me a lot. They don't sell a lot of those or they'd have it in stock. I didn't want to roll the dice on $90, so I got the eBay sensor for just under $30. There were crank sensors for this truck listed for as low as $12 brand new shipped on there, so I didn't completely cheap out. The verdict is still out on whether or not I ordered the sensor wrong or if it was produced or advertised wrong. I'm waiting to hear back.

The OEM Dodge crank sensor was ordered online and will be here this week for $103. If it fixes this problem just remember when you're working on Dodge junk- always use OEM sensors.

[86T3]

John, i never saw that it would help to give my experience since you were always heading in the direction of the crank sensor, but I'm sure you remember the problems I had with my cummins last year when I used an AutoZone crank sensor. Over the course I've 5 or 6 years that I owned that truck, i believe I put 1 Napa crank sensor in (lasted 3-4 years), and 2 AutoZone ones (1 lasted a year, the other 1 week). I ordered the cummins/dodge one and haven't had any problems since. I hope you didn't have to remove a 40lb started like I did to replace the sensor, and I hope that solves your problem

[fabiodriven]

I didn't recall your personal experience Joe, but it seems to be par for the course. Seems like every Dodge owner has been through this. I still would have rolled the dice on the aftermarket sensors because this truck is just a winter beater, I don't have a lot of money, and I went to the school of hard knocks and have to experience everything for myself.

Thankfully the crank sensor in this truck is pretty easy to get to and replace. What is incredibly stupid is the amount of bolts, as well as the starter, which need to be removed in order to remove the clutch inspection cover. It's a friggin inspection cover, not a stressed member. My Ford has two 10mm head bolts that have to be removed and the inspection cover comes right off, two. The Dodge has two 7/16 head bolts, three 5/8 head bolts, and at least two if not three more bolts that hold the starter in, which can then be removed in order to remove the inspection cover. I've been under a lot of trucks, this is just a stupid way to engineer such a simple part.

[86T3]

Another reason I didn't mention it was I kind of assumed it was Apple's to oranges.

Hey man, don't hate the player, hate the game. Lol. Ford has done plenty of dumb stuff too, don't forget. I really hope that sensor cures your problems. Any chance you can get reimburses for the eBay sensor purchase? I'd look into it at least

[fabiodriven]

I would have guessed apples and oranges as well with the difference between the gas and diesel trucks, but in retrospect it's the same exact issue it seems. It's unfortunate that Dodge is able to bring even the venerable Cummins diesel to a halt with their infected parts.

Getting reimbursed on the aftermarket crank sensor will depend if I ordered it wrong, they listed it wrong, or it was produced wrong. I tend to think it was produced wrong because it had the same shape and indent as the factory sensor, however it was slightly bigger than the factory sensor. I think I ordered it right and I'll be reimbursed, but we'll see.

[86T3]

It seems if it made contact with the trigger it was made wrong, Lol. I hope they see it the same way

[Rob Canadian]

Hope the OEM sensor fixes it up for you.

Can you post up a picture of the sensor that came in contact with the flywheel? Prices are ALL over the place as far as aftermarket and OEM. Had a customer that needed a starter. Aftermarket was $200.00 more than a OEM one. OEM one needed to be ordered and would take a couple days as it was a Saturday. Customer needed his vehicle on the road as it was his only car. Paid the $200.00 extra for the aftermarket starter.

On a side note. I love the diagnosis. It could be the sensor, wiring or ECU... THANKS!!! LOL

[fabiodriven]

Picture as requested!

https://uploads.tapatalk-cdn.com/20171114/e8f0cd84257ef2374035694d3e74ba5b.jpg

[fabiodriven]

In the end the problem was a faulty crank sensor. Brand new OEM replacement unit cured the problem. Never, ever put aftermarket sensors in a Chrysler product.

[Rob Canadian]

Good to hear you fixed the problem.

Aftermarket has come a long way in the last couple of years. I have a couple Toyota's. Seen aftermarket stuff have OEM boxed inside of it. O2 sensors. Made by Denso. Same colour of wires. Same length. Maybe a 2nd line. IDK. They have worked well in the past.

_line you got it fixed up. :)