P0340 P1391 help

[RLynnDay]

P0340 P1391 help
Ok guys, I need some help. I'm an experienced amateur, being the daughter of a mechanic and having worked on my own and friends/family's vehicles for almost 30 years - but this darn Dodge has me befuddled.

Awhile back I had some problems with a crank/no start which ended up being the camshaft position sensor aka distributor pickup coil on my 01' Ram 1500, 6cyl, 3.9L engine.
At the time, I'd been through every possible repair, replaced both cam and crank sensors, all plugs, wires, cap & rotor, and finally resolved the problem.
Here it is about 18 months later, and I started having some surging and jerking, stalling and misfiring, mainly after the engine warmed up. I had p1391 code, so I could often let the truck cool down, clear the codes,
and drive to wherever I needed to go around town. (I'm in a small town, so leaving town to go elsewhere means 15 minute 18-20 mile highway trip I don't risk)

Ultimately this time around, I replaced the cam sensor, and drove it fine for half a day, including out of town, and it seemed better than it had ever been. Later that night I tried to go down the block and it started
it's surging and jerking and stalling and super long crank times again, but I got it back home. Then I replaced the crank sensor. Small temp improvements, but back to the same, and had to be towed home.
(I should specify that I've used O'Reilly parts, with lifetime warranties - so I didn't have to pay to replace them this time around - they were already under warranty, and O'Reilly is all we have here in town, so that's why I use their parts I know, not the best choice but...)

So it will start and run, for while, and then it starts its herking and jerking.

I have a cheapy Innova code reader and a digital multimeter for diagnostics - so I got the dmm out and checked, and the output voltage from the sensor with the engine running varies between 1.75 and 3.45, never gets near the 5V....

BUT I backprobed the harness connector and found what do you know, but I have no continuity between the ground wire and supply 5v wire. With what little I know about electronics and voltages, etc. it seems like the signal from the PCM to the sensor isn't coming in as the full 5V reference it should, so that would affect the output range? Am I right? Or does the sensor not care much about the input reference voltage signal?

Where do I go from here?

Can the plastic connector (and inside) being dirty cause this? Would it be worthwhile to try cleaning it?

Can I just replace the plastic connector, or is there more testing of the rest of the wiring between it and the PCM that must be done?

The wiring *appears* in decent shape, with no obvious splits or breaks in wiring, melted insulations, etc.


*Also, at a later date, I have a code for a Governor's Pressure Sensor that I need to take care of, but right now my concern is getting the truck running and driving.

I'd appreciate ANY help you can give! Thanks in advance

 

[RLynnDay]

HELP?? Need help with p0340 and p1391 codes on 01 dodge ram 3.9L 6cyl. Have replaced cam sensor (distributor pickup coil) 3 times and crank sensor. Truck runs fine when cold, but after fully warmed up, it surges and jerks and stalls, making odd noises like a misfire (or maybe timing chain sounds) and triggering CEL and p340 and p1391 codes. I've been told that I may need someone w a certain scan tool to do a distributor sync, but when I had issues with these 18 months ago and replaced both sensors then, I never had to do that. I just put the new parts on (then) and problem went away.
Parts are from O'Reilly, which I've been told that these trucks "dont like" aftermarket parts, but Mopar has discontinued this cam sensor and it isn't available. (What does that tell ya?!)
Besides three parts in a row can't all be defective can they? But I just can't seem to figure out why it **only** acts up when its warm? Would timing chain only act up when warm? And would it trigger the 340 code?

 

[Okiespaniel]

Welcome to RF!

Diagnosis over the web is dicey at best, but lets consider a couple of things.

Supply voltage to cam sensor... Is it 5 volts? If it is, then you have either a pcm or wiring issue. Or both! Check your supply voltage cold and then when things go to shyte. It's possible your pcm can no longer take the heat.

If a test wire doesn't give you the voltage you need out of the pcm directly, then your pcm is going out.

You shouldn't have to mess with your fuel sync unless you moved the distributor or you actually have timing chain issues, like jumping teeth.

I don't know if you've replaced your timing set, but if you have over 100k and haven't, you may wish you had.

The same thing applies to your 1391 code. It simply says that the cam and crank sensor don't agree with each others timing, and the thing between them is the timing set. But again, if your supply voltage isn't where it should be, you likely have other problems you should address.

I would guess ( and again that's an internet guess) that your pcm is overheating. Try this, when the truck starts to buck, shut it off, remove the pcm and stick it in your refrigerator or freezer for about 7-10 minutes to flash cool it. Then put it back on the truck while it's still hot, and try to start it. If it runs fine until the pcm gets hot, it's probably your pcm.

And again, with the internet assumption(s) that your battery/charging system is up to ***** because low voltage is bad.

 

[RLynnDay]

Ok I'm confused...if it IS 5 volts supply from PCM to Cam sensor, then the problem is the PCM or wiring? Isn't it supposed to be 5v? Or do you mean coming from the sensor and going to the PCM? It's a 3 wire hall effect sensor. The voltage with engine running (normally, before it starts going haywire) is between 1.75 and 3.5 volts - which of course, the dmm doesn't update as quickly as the square wave, so it's difficult to ascertain with dmm.
I have not tested voltage on the supply wire going TO the sensor because I wasn't sure if I needed to test it with the vehicle running, cranking, key on of off? And I'd seen conflicting reports of whether it was safe for PCM to do so.
Should I feel the PCM itself when/after the truck starts acting up, to see if it is hot?


Yeah, I wondered, because last time I didn't have to do anything but put the parts in. I know I do need to replace the timing set, but I am not looking forward to it, that's for sure!

Thanks so much for your input,. though!! I will check the PCM!~

 

[RLynnDay]

SO...what it finally ended up being was - get this- a defective aftermarket crank sensor from O'reilly. Bought the MOPAR part, installed and ****, 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!

 

[Okiespaniel]

One of things that a lot of folks have to learn the hard way is to not buy discount auto parts.

I rarely buy sensors form anyone but a dealer, occasionally NAPA, because some parts are OEM sourced through Delphi. Delphi is an OEM supplier. I usually avoid Echlin. I can tell you Echlin, Borg Warner/ Niehoff, and Standard ignition are currently owned by the Affinia group, so all those names have a center corporate source. Any private label part purchased is made through one of these sources.

 

[kad]

SO...what it finally ended up being was - get this- a defective aftermarket crank sensor from O'reilly. Bought the MOPAR part, installed and ****, 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!

Glad you got it fixed. I learned that lesson with my wife's Jeep Liberty. It kept burning through aftermarket Transmission Oil Preasure sensors. Put a Mopar one in and 3 years later when we sold it it was still working fine. Mopar vehicles, in particular, seem to be very fussy about aftermarket sensors.

-K

 

[Yeret]

Yeah, I've had various issues with O'Reilly stuff in various vehicles over the years. I've pretty much decided to go genuine OEM whenever possible with my truck's electronics.

I replaced my crank sensor a couple years back with an O'Reilly one. Anyone's guess how much longer it'll last, eh?