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Dodge P0340 HELP?

  • therebeenthatdun
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29 Mar 2019 22:12 #28220 by therebeenthatdun
Dodge P0340 HELP? was created by therebeenthatdun
Hi all! I'm hoping someone can help because I'm baffled..

About 7 weeks ago, my 2001 Dodge Ram 1500, 6cyl 3.9L started acting up. Threw a P0340 and P1391 code. So I replaced BOTH cam sensor (pickup coil) and crank sensor, which were both under warranty from the aftermarket parts I put on 18 months ago when she would act up and not start back up when warm. Didn't fix it. Replaced cam sensor again. Same thing. One more time, same thing...

Until now I've only had a cheapy Innova code reader and digital multimeter to work with, and just got a BAFX bluetooth scanner, but...

The scanner does not check the cam or crank signals without specific custom PIDs, which I cannot find for the life of me...

so I've just checked the o2 sensors, and surprisingly, they seem ok. They move evenly between about .3volts and .6 volts, going up just past .9 volts with a spray of carb cleaner in the hose. But on the scanner's tests, I did get a test failure for the upstream sensor, after it was warm and things were going to shyte - so I'll unplug the sensor and let it feed off factory defaults and see if that makes any difference...

In the meantime,

However, what I've discovered through just plain driving is this -- I can start the engine cold, and drive as long as I want (theoretically - today I drove 30+ minutes, 20+ miles), with no symptoms at all. BUT...once the engine is warmed up and has been turned off, starting the truck back up results in a P0340 code, erratic signals from the cam sensor, (which then means) erratic signals from the crank sensor, misfires and super rough idle with random stalling.

I had to keep my appointment today (a required doctor appt) out of town, and made it there with no issue, and then despite waiting 2+ hours, killing time at Wally World and an awesome thunderstorm cooling the truck down, the cam sensor must have still been warm/wonky, because as soon as I started it back up to go home, I got the p0340 code, misfires in cylinders 1, 3 and 5, ultra lean conditions where I thought it was going to stall out, and a few times I think it may have temporarily, because I felt my power brakes lose the 'power' as I drove (despite going 55+ mph down the rural highway) but I DID make it home, 20+ miles.

AND THEN...(wait, this story isn't over just yet LOL)...as I pulled up in front of my house, I hurried, expecting it to stall as I pulled up and went to shift into Park - but then it all evened out, no more misfires, no more rough idle. I had planned on taking it around the block to see what she did, but just then my cat jumped in the cab with me, rubbing muddy paws all over the groceries, so I decided just to go on in the house for the night LOL. Haven't been back out to mess with it since...

But, given this trip and information, I just keep coming back to the cam sensor/pickup coil...I watched a YouTube video from a guy named ScannerDanner with the same basic problems I'm having, except in his video, the truck in question would not start back up when warmed up....



Starting cold, it works fine. Proper signals to crank sensor, proper signals from crank to PCM, no crazy symptoms. Of course, once the engine is running, it doesn't need the cam sensor info much anymore - the crank sensor does it all, sending signals to PCM based on what the cam sensor said when starting. But once it's all warmed up, the cam sensor sends bizarre signals, if any, to the crank sensor, which then sends whatever it does back, and all hell breaks loose.

Again, I've been told not to use aftermarket parts, but this cam sensor/pickup coil from MOPAR has been straight up discontinued. Not a single soul around has one. Except junkyards, and I'm not sure I want a used one, given the failure rates...So then what brand if any can I trust??? I've been through 3 BWD sensors in 7 weeks, all with this set of symptoms.
I can get a MOPAR CRANK sensor, but it's a b1tc4 to get to, so I hate to go through that if it isn't proven to be the problem....
I love my truck and am not ready to give her up, but I just don't know what to do with her!

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30 Mar 2019 08:09 - 30 Mar 2019 08:13 #28225 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic Dodge P0340 HELP?
I think you are 100% right with the cam sensor although I haven't looked at any Chrysler vehicle for years heat soak causing loss of cam position sensor signal is a symptom I have seen often with other manufacturers engines. In fact I carry a spare cam sensor for my current dally driver,
While it is comparatively easy to diagnose a sensor that is completely dead without an oscilloscope there is no easy way confirm an erratic signal.

Sorry I can't help you with a supplier of decent quality parts but someone else might have an idea ....

"It is the nature of every person to error, but only the fool perseveres in error." Marcus Tullius Cicero
Read more at: www.brainyquote.com/authors/marcus_tullius_cicero



Last edit: 30 Mar 2019 08:13 by Andy.MacFadyen.
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30 Mar 2019 09:52 #28231 by juergen.scholl
Replied by juergen.scholl on topic Dodge P0340 HELP?
I am with Andy , this is very probably the cam sensor. You might want to disconnect the cam sensor when it' starts running erratically annd see if it smoothes out left alone with the crank sensor.

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
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30 Mar 2019 14:51 #28248 by therebeenthatdun
Replied by therebeenthatdun on topic Dodge P0340 HELP?
Thanks so much guys! My question then is this - If I am on the right track with it being the cam sensor...why is it that 3 aftermarket parts in a row, in 7 weeks, are ALL bad? I've been told to stick to MOPAR, but the MOPAR has been discontinued and all I can find are these aftermarket parts. Is it really possible that all of them are bad?
Since the O2 sensors likely need replaced anyway, but aren't throwing their own code - can they affect the cam sensor voltage? I know some of the sensors share their 5volts with other sensors, but would that affect the signals being sent back to everything else, and how would I know?

As far as disconnecting the cam sensor when it's running erratically, would that help if it had already sent the screwy signals (upon starting)?

I've checked all of the wire connections and don't see any broken or damaged wires or insulations, but when I first checked with the multimeter, I have no continuity between the ground wire and supply 5v wire. Someone told me that I wouldn't, or wouldn't need it?

Is there an easy way to check the crank sensor? I only replaced it once with an aftermarket...could it be the problem, sending bad signals back when its warm? Or would that cause problems at soon as it warmed up while running?

Like 18 months ago, the truck stalled out on the highway and wouldn't start back up, and I had replaced both cam and crank then, but it turned out the crank was the problem at that time - but it would die out while driving, as soon as it got warm. (Unlike this time where it will keep running and driving while warm, until you turn it off and start back up while warm)

I have looked this up and researched everything I can find online for the past 2 months - enough to know that this is not an unusual issue, and while a couple people have brought up the EVAP codes I've had since I bought the truck 7 yrs ago, I'm confident those are not the problem. Granted, fixing them will help, but they are not the cause of the issue at hand...and everything keeps leading me back to these sensors. I just want to know which and what to do before spending more money I don't have LOL

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31 Mar 2019 06:44 #28280 by Monde
Replied by Monde on topic Dodge P0340 HELP?
This might help:

File Attachment:

File Name: CrankDescr...tion.pdf
File Size:185 KB

File Attachment:

File Name: Camoperation.pdf
File Size:187 KB

Vouloir, c'est pouvoir.
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31 Mar 2019 13:30 #28309 by therebeenthatdun
Replied by therebeenthatdun on topic Dodge P0340 HELP?
I appreciate the effort, but no, it doesn't. I know what they each do, or are supposed to do. My problem is that after replacing them both, the issues remain, and only when starting the truck again ater having driven it and turned the engine off.
All signs point to the cam sensor, but it's been replaced 3 times. Crank sensor once. No change in symptoms.

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31 Mar 2019 20:59 #28332 by Monde
Replied by Monde on topic Dodge P0340 HELP?
I was just trying to show that the truck needs the cam sensor at all times, not only at start up. To my understanding, the cam sensor is responsible for fuel and the crank sensor for spark. When the truck does not start, if you check spark and fuel and find spark, I would lean towards cam sensor and if you find injection pulse, I would lean towards the crank sensor.

Vouloir, c'est pouvoir.
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31 Mar 2019 22:54 #28337 by therebeenthatdun
Replied by therebeenthatdun on topic Dodge P0340 HELP?
So far, I have not had a no start condition. It starts fine. When I've been driving, turn it off and start it back up while it's still warm, it starts rough, but it does start. The warmer it is, the rougher the start -- but the sync is clearly off between the cam and crank, because there are misfires on at least a couple cylinders and it tries to stall out, feeling like a super lean ratio.
Just also for reference because someone else mentioned a plenum gasket leak could cause issues, I've checked mine, and no obvious leaks. No sucking sounds, etc.
every single thing I read or learn leads me back to these two sensors. Since I've replaced the cam (pickup coil) 3 times and the crank sensor only once, that seems like the logical next step, to buy a new brand/from a new supplier, and hope for the best. In all actuality, I haven't been throwing money at it yet - just time - because both sensors were/are under warranty. I suppose it's entirely possible that the "new" crank sensor I installed was defective out of the box. I've had it happen before with GM igntion modules, so I know it happens. (You would think that manufacturers would ship their sensitive electronic products to stores with an extra degree of caution, because heat, jostling, etc theoretically could damage them in transit.)

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11 Apr 2019 00:37 #28563 by therebeenthatdun
Replied by therebeenthatdun on topic Dodge P0340 HELP?
SO...what it finally ended up being was - get this- a defective aftermarket crank sensor from O'reilly. Bought the MOPAR part, installed and POOF, problems gone. I will never again buy aftermarket sensors of any kind unless I absolutely have to.

I noticed as I was installing the new Mopar one, that the magnet on it kept trying to latch on to every single piece of metal in the engine compartment. The O'Reilly part would not even pick up a paperclip or small keyring. Barely had a magnet in it at all. If I'd noticed that installing it in the first place, I could have saved a lot of aggravation. Live and learn. Thanks to all for the help along the way!
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