Cam Sensor P0340 Unsolved after 4 months!

[solongjoe]

Hello smart 4 Gen Ram owners. 2014 Ram 1500 5.7 (rebuilt engine (lifter failure 3 years 60k miles ago)) total mileage 181k December 2025, throwing P0340 code, goes into limp mode. Replaced cam sensor with generic, code comes back 2 weeks later. Replace cam sensor with OEM part. Lasts about a week. Took to local mechanic, intermittent signal loss. He suggests wiring damage at sensor, repairs that, replaces one coil too ($600). Lasts about a week, code back on, limp mode. I replace the pigtail going to cam sensor, again last about week. I read that oil change with OEM filter may fix. I replace oil with OEM filter. Lasts about 6 weeks, code is back. Take it to the dealer January of this year (recommended by another service advisor). I suggested it was the engine wiring harness (they reject that out of hand) First thing they say is the generic pigtail is the problem. The replace that all the way back to the PCM ($1,200). Lasts a few days for CEL back on. They have it for 6 weeks, saying they are talking to STAR. The factory says it's the cam phaser (I thought unlikely since that part was not that old since it was part of the rebuilt engine). This part was partially covered under the engine warranty. I paid $3,000 net after refund from engine warranty company. Lasted less than 24 hours before CEL returned. STAR says it's either the cam shaft (which they could have replaced or at least inspected when they replaced the phaser) or the PCM. They suggest cam first then PCM. They want more $. I suggest I pay for the PCM which I find reconditioned and programmed for $160. They agreed. They replace the PCM I paid for (no charge). Lasted 24 hours for CEL return. Now they want another $260 to diagnose. What the heck! What to do????

 

[Ken226]

The circuit they are testing is pretty simple. When you say "CEL return", assuming the same code every time?


So, they have tried new wiring from the PCM to the Sensor? They've tried a new sensor 2x, and they have tried another PCM? The exact same problem returned each time?

If that is the case, then everything involved in that entire system has been replaced except the reluctor wheel, which is mounted on the cam phaser on the front of the camshaft.

Then, yea. That might be the next thing i'd be looking at too.


But,









Now, assumptions are variables and historically cause alot of problems to be passed over and not be solved. You know the old saying, "ASSUME" makes an ASS out of U and ME.


The wiring from the sensor to the PCM included the terminals inside the C2 connector on the PCM, that would be pins 87, 66 and 85. Did they drag test those terminals? de-pin those terminals and replace them, inside the connector? Or, did they snip the wires and splice in a replacement section, leaving the old terminals?

Because the intermittent nature of this problem would have be inspecting the pins at both ends of this circuit, really really well! Since the sensor end "pigtail, i guess", has been replaced, that kinda points to the other end. Loose pins/terminals inside a connector are amongst the most common intermittent electrical problems, and most difficult to find.

pin drag

intermittent open circuit fault with air flow sensor due to loose pin at engine control unit plug

youtu.be

The diagram above shows two splices in the harness. Splices sp1631 and sp1106 would also be worth looking at.

 

[EdGs]

Bad VVT (oil control) solenoid? It does control the cam phaser, I believe.

I know on mine the little plastic cap inside the connector came off, and would fall off when I unplugged it from the VVT solenoid.

I did not replace it, but made sure it was on when I reconnected it to the solenoid.

The way I found it was I noticed the push-on wire tie mounts for the MDS and VVT harness were broken. I found a couple small pieces of them on top of the block, and I had previously vaccumed, so I checked inside my shopvac and found the remaining pieces of them, along with that little cap from the VVT connector.

I looked because after only finding part of them, all I could think was that they fell into the oil galley when I had the MDS solenoids out. Needless to say, after I found all the pieces, they went missing like Jimmy Hoffa.....lol.

I wasn't sure what that little white cap was from at first, until I looked at those connectors closer.

I had no idea it had fallen off the connector, either.

 

[solongjoe]

Thanks all! I will forward your suggestions! The oil control solenoid is under the intake manifold (another item they could have checked since the replaced the intake manifold gasket) as part of these repairs since they said it was leaking oil.

 

[EdGs]

Thanks all! I will forward your suggestions! The oil control solenoid is under the intake manifold (another item they could have checked since the replaced the intake manifold gasket) as part of these repairs since they said it was leaking oil.

Yes it is under the intake, at the very front, on it's side, facing forward.

 

[BigTerry66]

Hello smart 4 Gen Ram owners. 2014 Ram 1500 5.7 (rebuilt engine (lifter failure 3 years 60k miles ago)) total mileage 181k December 2025, throwing P0340 code, goes into limp mode. Replaced cam sensor with generic, code comes back 2 weeks later. Replace cam sensor with OEM part. Lasts about a week. Took to local mechanic, intermittent signal loss. He suggests wiring damage at sensor, repairs that, replaces one coil too ($600). Lasts about a week, code back on, limp mode. I replace the pigtail going to cam sensor, again last about week. I read that oil change with OEM filter may fix. I replace oil with OEM filter. Lasts about 6 weeks, code is back. Take it to the dealer January of this year (recommended by another service advisor). I suggested it was the engine wiring harness (they reject that out of hand) First thing they say is the generic pigtail is the problem. The replace that all the way back to the PCM ($1,200). Lasts a few days for CEL back on. They have it for 6 weeks, saying they are talking to STAR. The factory says it's the cam phaser (I thought unlikely since that part was not that old since it was part of the rebuilt engine). This part was partially covered under the engine warranty. I paid $3,000 net after refund from engine warranty company. Lasted less than 24 hours before CEL returned. STAR says it's either the cam shaft (which they could have replaced or at least inspected when they replaced the phaser) or the PCM. They suggest cam first then PCM. They want more $. I suggest I pay for the PCM which I find reconditioned and programmed for $160. They agreed. They replace the PCM I paid for (no charge). Lasted 24 hours for CEL return. Now they want another $260 to diagnose. What the heck! What to do????

I don't know if it the same condition.. my 2008 ram with hemi had same problem..ran the code wish gave me a list of could be problem.. first two on the list was temp sensor .. replace didn't help the next code was crank sensor which help for a couple if days... person on another Mopar board he a mechanic at a dodge dealership in ft worth told me I need to replace crank and cam sensor this will fixed the problem and sure enough it did no more problem. The mechanic told me the way dodge has done with the harnesses is one senor go out it throw all the voltaged off to all the others sensors. .I alway knew dodge wireharness are a pain in the rear.. never thought the newer truck be that bad... I hope this help...

 

[Dusty]

I don't know if it the same condition.. my 2008 ram with hemi had same problem..ran the code wish gave me a list of could be problem.. first two on the list was temp sensor .. replace didn't help the next code was crank sensor which help for a couple if days... person on another Mopar board he a mechanic at a dodge dealership in ft worth told me I need to replace crank and cam sensor this will fixed the problem and sure enough it did no more problem. The mechanic told me the way dodge has done with the harnesses is one senor go out it throw all the voltaged off to all the others sensors. .I alway knew dodge wireharness are a pain in the rear.. never thought the newer truck be that bad... I hope this help...

Won't argue with the resolution, but I don't buy the rationale.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 149573 miles.

 

[Sherman Bird]

Wow! Everything except the correct thing has been done, eh?
Has anybody gotten out their 8 channel DSO (digital storage oscilloscope) and DIAGNOSED the entire engine control system?
I mean, getting back to fundamental basics is called for at this point.
My first move would be to apply some basic observational tactics.

Check that the battery isn't sulfated, or that the alternator isn't putting excessive A/C ripple out.

How about the reman engine being painted? And that paint not being considered when the various ground wires were attached, and there being feedback due to high resistance at those points?
Voltage drop checks would lead to that, if it were the case. I generally remove ALL paint in the places where ground wires go, AND add star washers upon reassembly.

The VERY next test I'm going to run is hooking up my DSO, and performing a relative compression test with a 600 amp inductive pickup is affixed to the negative battery cable, close to the battery, whereby the accelerator pedal is floored for "clear flood", and the engine cranked. I'm going to set up my trigger for single capture, then look closely for secondary ignition "ghost/phantom" events in the cable.
IF I find the phantom damped waves, I'll measure them for time. 60 Hz means the overhead shop lights are being picked up; a phenomena of flourescent lighting. When the time element is about 5Kz, THAT is ignition feedback. I'm going to then hook up another channel and tie into the number 1 ignition coil trigger wire, and repeat the test.

With using my firing order and setting up my rulers, I can determine WHICH coil is back feeding into the electrical system. I see this issue very often, yet, very very few shop diagnosticians have an inkling as to how valuable and time saving this step is. And by firing the coils "dry" in clear flood, they are stressed and if there IS a problem, it will show up.

There... I shared a couple of places I would start out from, if I were diagnosing the problem.
I get problems such as this routinely, and did so just this past weekend. Other shops throw wild guess repairs at the car, and nothing gets fixed.

I hope this gets you to thinking, critically. Good luck!

 

[RedSRT4Me]

Hello smart 4 Gen Ram owners. 2014 Ram 1500 5.7 (rebuilt engine (lifter failure 3 years 60k miles ago)) total mileage 181k December 2025, throwing P0340 code, goes into limp mode. Replaced cam sensor with generic, code comes back 2 weeks later. Replace cam sensor with OEM part. Lasts about a week. Took to local mechanic, intermittent signal loss. He suggests wiring damage at sensor, repairs that, replaces one coil too ($600). Lasts about a week, code back on, limp mode. I replace the pigtail going to cam sensor, again last about week. I read that oil change with OEM filter may fix. I replace oil with OEM filter. Lasts about 6 weeks, code is back. Take it to the dealer January of this year (recommended by another service advisor). I suggested it was the engine wiring harness (they reject that out of hand) First thing they say is the generic pigtail is the problem. The replace that all the way back to the PCM ($1,200). Lasts a few days for CEL back on. They have it for 6 weeks, saying they are talking to STAR. The factory says it's the cam phaser (I thought unlikely since that part was not that old since it was part of the rebuilt engine). This part was partially covered under the engine warranty. I paid $3,000 net after refund from engine warranty company. Lasted less than 24 hours before CEL returned. STAR says it's either the cam shaft (which they could have replaced or at least inspected when they replaced the phaser) or the PCM. They suggest cam first then PCM. They want more $. I suggest I pay for the PCM which I find reconditioned and programmed for $160. They agreed. They replace the PCM I paid for (no charge). Lasted 24 hours for CEL return. Now they want another $260 to diagnose. What the heck! What to do????

Burn it. Get the insurance money and get another truck