The Dreaded P0340

[The (LJ) Dude]

2006 4.0

Well…after sitting a month or more this code showed up out of the blue. Swapped crank and cam sensor for Standard Motor cam & Mopar Crank PS. No real change.

Long cranks when cold, yet starts easily enough when warm.


I have reviewed the below.

https://wranglertjforum.com/threads/how-to-test-your-camshaft-position-sensor.68487/


*What I was NOT expecting to see is 5v on the signal wire - AND the 5v supply wire. Does this indicate a problem in wire harness?*

PS- best I can tell, Standard Motor is who makes the Cam sensor for Napa.

 

[Chris]

2006 4.0

Well…after sitting a month or more this code showed up out of the blue. Swapped crank and cam sensor for Standard Motor cam & Mopar Crank PS. No real change.

Long cranks when cold, yet starts easily enough when warm.


I have reviewed the below.

https://wranglertjforum.com/threads/how-to-test-your-camshaft-position-sensor.68487/


*What I was NOT expecting to see is 5v on the signal wire - AND the 5v supply wire. Does this indicate a problem in wire harness?*

View attachment 575272

View attachment 575273

PS- best I can tell, Standard Motor is who makes the Cam sensor for Napa.

Given that you're seeing 5V on both the signal wire and the supply wire, it does suggest there might be a short somewhere in the wiring harness or a potential issue with the PCM.

Here are a few things you might want to check:

1. Closely inspect the wiring harness for any signs of wear, fraying, or damage. A short between the power and signal wires could cause the readings you're seeing.

2. Ensure that the camshaft position sensor has a good ground connection. A poor ground can lead to erratic sensor behavior.

3. You might want to test the resistance of the sensor itself and the wiring between the sensor and the PCM to rule out any internal shorts.

4. If you have access to a scan tool, check the live data from the PCM to see if it is receiving the correct signals from the cam sensor while the engine is running.

5. Sometimes these faults can be intermittent. If you haven't done so already, keep an eye on the codes while the engine is cold and see if the issue changes after a few cold starts.

If all else fails, you might need to consider the possibility of the PCM being at fault, especially if everything else checks out. @Wranglerfix is the go to guy for PCM testing and replacements.

 

[OldBuzzard]

I don't know about this sensor, but some (many?) sensors do expect 5V on the signal wire. It's pulled up to 5V by a resistor in the PCM, and the sensor's job is to pull that signal line down to ground periodically to produce the signal.

 

[Pascal25]

I don't know about this sensor, but some (many?) sensors do expect 5V on the signal wire. It's pulled up to 5V by a resistor in the PCM, and the sensor's job is to pull that signal line down to ground periodically to produce the signal.

I found this to be the case for CKP, at least on a 2005 2.4L. Operates like NPN rather than PNP

 

[OldBuzzard]

I found this to be the case for CKP, at least on a 2005 2.4L. Operates like NPN rather than PNP

Yes. And the Vehicle Speed Sensor works this way.

 

[The (LJ) Dude]

Hmmm. Have been looking at wiring suspiciously…nothing glaring has turned up yet hunting through loom. Already have a Wrangler fix pcm.

Guess I better backprobe the sensor while hooked up see if that 5v drops out.

Correct me if wrong - doesn’t the same circuit that supplies the CamPS 5v…also supply some of the other sensors?

I’m theorizing that if those two were shorted…other issues would arise?

Thanks everyone for chiming in.

 

[Pascal25]

Hmmm. Have been looking at wiring suspiciously…nothing glaring has turned up yet hunting through loom. Already have a Wrangler fix pcm.

Guess I better backprobe the sensor while hooked up see if that 5v drops out.

Correct me if wrong - doesn’t the same circuit that supplies the CamPS 5v…also supply some of the other sensors?

I’m theorizing that if those two were shorted…other issues would arise?

Thanks everyone for chiming in.

That's correct that the +5V is shared with other sensors, but if it was shorted to the CKP signal wire, I suspect it doesn't really have the drive strength to ruin everything else.
However, I don't think it's shorted, and you'll probably see it pulsing if you do measure while the engine is cranking

 

[The (LJ) Dude]

That's correct that the +5V is shared with other sensors, but if it was shorted to the CKP signal wire, I suspect it doesn't really have the drive strength to ruin everything else.
However, I don't think it's shorted, and you'll probably see it pulsing if you do measure while the engine is cranking

I did randomly have a zero oil pressure reading yesterday at startup - never happened before. Restarted, and it was gone. Not inclined to suspect a hardware issue with 20k on rebuild with new oil pump, and new Crown OPDA.

I have heard of bypassing the loom and splicing in a new wire from PCM. Had to do that with ground wire in loom for one bank of o2 sensors. Will start with back-probing tomorrow in daylight and report back...

As a daily driver/work vehicle...this is getting tiresome. And has me daydreaming about a future mechanical Diesel swap

 

[ItchyDong]

5 volts on the signal wire unplugged is exactly what you’re hoping to see. Research “bias voltage”. It’s how the PCM knows when there’s an open circuit.

 

[Wranglerfix]

The p0340 is the pcm most of the time. How is your shifting from 1st to 2nd when cold?

 

[MFMauceri]

P0340 Code - Try this first, and cross fingers:

I had the same condition. Two things: The code is about a faulty SENSOR. That's actually the rotating magnet gizmo shown in one of the photos here. Odds are it's worn down over time and eventually dislodges or fails (conditions vary). Do ONLY remove the electronic sensor (quik-clip and two small bolts), do not remove camshaft synchronizing "shaft" (yet). If the magnet is dislodged, you can reposition and reinstall and see what that gets you (possibly driving away). Else, repace with a new one (about $46).

Do not be tempted to (at first) take OUT the entire camshaft syncing shaft, because it needs to be finessed back IN, and I do mean a lot of trial and error, because you have to get the motor back to TDC on cylinder 1 to get it in correctly-- it WILL slide out from any position though... and if your timing marks are worn down-- like mine were-- then it's a BIG PITA. Try just the sensor portion first, so the synchronizer shaft stays aligned. The sensor swap is a 5 minute job. The sychronizer realign is... uh, NOT.

 

[The (LJ) Dude]

P0340 Code - Try this first, and cross fingers:

I had the same condition. Two things: The code is about a faulty SENSOR. That's actually the rotating magnet gizmo shown in one of the photos here. Odds are it's worn down over time and eventually dislodges or fails (conditions vary). Do ONLY remove the electronic sensor (quik-clip and two small bolts), do not remove camshaft synchronizing "shaft" (yet). If the magnet is dislodged, you can reposition and reinstall and see what that gets you (possibly driving away). Else, repace with a new one (about $46).

Do not be tempted to (at first) take OUT the entire camshaft syncing shaft, because it needs to be finessed back IN, and I do mean a lot of trial and error, because you have to get the motor back to TDC on cylinder 1 to get it in correctly-- it WILL slide out from any position though... and if your timing marks are worn down-- like mine were-- then it's a BIG PITA. Try just the sensor portion first, so the synchronizer shaft stays aligned. The sensor swap is a 5 minute job. The sychroninzer realign is... uh, NOT.

View attachment 575529

Looks like you have on 04 or earlier...sadly I have the 05/05 incarnation (OPDA).

They look like this for anyone wondering:
https://www.quadratec.com/sites/def...o_large/public/customer/products/IMG_1163.JPG

 

[The (LJ) Dude]

The p0340 is the pcm most of the time. How is your shifting from 1st to 2nd when cold?

can't say I notice anything.

I seem to be getting good voltage & ground from pcm. Course this does not speak to the quality of the path.

 

[The (LJ) Dude]

@Wranglerfix - do you know if the 04 and earlier camshaft sensor/oil pump drive assembly outputs a different wave form? If so...how difficult would it be to re-program one of your pcm to recognize that instead of the crappy 05/06 OPDA setup. Say, matched to a reliable sensor such at the NTK....like i run on my 04 Cherokee with 4.0

Seems to me you would have a wonderful conversion package to offer....with demand increasing as more and more original sensors fail...

 

[The (LJ) Dude]

That's correct that the +5V is shared with other sensors, but if it was shorted to the CKP signal wire, I suspect it doesn't really have the drive strength to ruin everything else.
However, I don't think it's shorted, and you'll probably see it pulsing if you do measure while the engine is cranking

ok so....

1) tested the original 2006 Mopar sensor today that this all started with....using screwdriver passed in front of sensor. Deader than a doornail.
2) Went back to what I thought was a Standard Motor sensor (I believe who makes the Napa branded version)....but re-looking I think it's actually a genuine Mopar....with box proudly stamped....made in China. This one starts it better than no or dead sensor...but still not great when cold. Anyway...it pulses when tested.

With limited knowledge on this topic...I'm starting to think of un-educated what-ifs. Like....what if Chinese timing chain kit with 20k on it has gone slack..wonder if that would add to the problem.

Testing sensors:
https://www.dropbox.com/scl/fi/tkco...ey=rbjemlzxvixm8e7z95dbwenmu&st=8nfvanvz&dl=0

 

[MFMauceri]

Looks like you have on 04 or earlier...sadly I have the 05/05 incarnation (OPDA).

They look like this for anyone wondering:
https://www.quadratec.com/sites/def...o_large/public/customer/products/IMG_1163.JPG

Yes, an '03. I posted this not so much to speak to your issue, but for others that may search out that code in the forum. Your odyssey, is, well, epic. You'll run it down, though.

Keep the faith.

 

[Bigfoot-NM]

ok so....

1) tested the original 2006 Mopar sensor today that this all started with....using screwdriver passed in front of sensor. Deader than a doornail.
2) Went back to what I thought was a Standard Motor sensor (I believe who makes the Napa branded version)....but re-looking I think it's actually a genuine Mopar....with box proudly stamped....made in China. This one starts it better than no or dead sensor...but still not great when cold. Anyway...it pulses when tested.

With limited knowledge on this topic...I'm starting to think of un-educated what-ifs. Like....what if Chinese timing chain kit with 20k on it has gone slack..wonder if that would add to the problem.

Testing sensors:
https://www.dropbox.com/scl/fi/tkco...ey=rbjemlzxvixm8e7z95dbwenmu&st=8nfvanvz&dl=0

https://wranglertjforum.com/threads/p0340-solved.42585/

Passing a screwdriver over the sensor doesn’t necessarily give you the entire picture.

 

[The (LJ) Dude]

https://wranglertjforum.com/threads/p0340-solved.42585/

Passing a screwdriver over the sensor doesn’t necessarily give you the entire picture.

Well...I have a Napa sensor on the way.

 

[The (LJ) Dude]

Here’s the latest!

1) Napa cam sensor resolves the long crank & coding for cam sensor. Eff that new Chinese Mopar sensor!! Napa sensor threw the cam/crank sync off like 3 degrees… which I clocked manually back to the below. *** strange to me - rotating the OPDA seems to make zero difference to how the engine runs - even tough cam/crank shows being out, as much as 15 degrees either way I have tried. ***

2) New brake booster resolved that vac leak and poor breaking. Thanks @mrblaine for advice there. No real change to uneven idle however sadly

3) Still runs like crap - see dropbox video attached. Does not seem like IAC type symptoms.

4) vacuum gauge says timing is late…always has. Hmmm

At this point, I’m thinking of pulling the timing cover to see if the Chinese timing chain kit has gone slack since rebuild 20k ago. Replacing with Melling if need be.

https://www.dropbox.com/scl/fi/26ir...ey=o5qpvlmm4ki8nk9x45jdfw1j2&st=wj2hylxc&dl=0

 

[Ascho7]

I did randomly have a zero oil pressure reading yesterday at startup - never happened before. Restarted, and it was gone. Not inclined to suspect a hardware issue with 20k on rebuild with new oil pump, and new Crown OPDA.

I have heard of bypassing the loom and splicing in a new wire from PCM. Had to do that with ground wire in loom for one bank of o2 sensors. Will start with back-probing tomorrow in daylight and report back...

As a daily driver/work vehicle...this is getting tiresome. And has me daydreaming about a future mechanical Diesel swap

So I recently did a frame swap, but a week before I replaced the OPDA with a crown opda, synced it up with a tool like you did to move it back to <0.5 degress cam/crank, reused original sensors etc. Had no problems whatsoever, jeep drove great. However, once I did the frame swap and buttoned everything back up, same thing. First start was no oil pressure, second start was good. Happens everytime, after the first start, kill it, restart within 30 secs and good pressure. Since then, I replaced timing chain and sprockets, oil pump, oil pressure sending unit (with mopar), and I'm still having the same problem. I've found one thread that describes the same issue where first start no oil pressure, second start is good and their fix was replacing the sending unit. Didn't work for me. I had to replace some vacuum lines going into the intake manifold and that solved my high/weird idle issues, but sounds like you've already gone through these. If you are having the same sort of issue, where every single time no pressure on first start, and only second, well I haven't found a solution yet, and besides a weird pcm or computer issue (mine is a WranglerFix), I'm really not even sure where to go next.