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Discussion Starter · #1 ·
2011 3.6. I got the P0340 code for the first time about a year ago. I reset it, figuring it was a one time issue. And it was, at least until it recently reappeared.

It reappeared about a month ago, and now the vehicle rattles about 50% of the time on startup, and the code will reappear.

Code scan showed it was Bank 1 Sensor 1, which is for the passenger side. So today, I replaced the old Camshaft Position Sensor with an OEM one. First 3 startups were good, but then had 2 straight rough starts with accompanying rattling sounds and check engine light showing up.

Same code as before.

So if it's not the sensor itself, what the heck could it be? Bad harness? How would I even test that? And if it's that, how would I go about replacing it?
 

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You need to get this sorted out ASAP as this could eventually damage the engine.
Other than the sensor being defective it could also be the reluctor on the camshaft itself that the sensor works with or hopefully a connector issue, an open circuit or short circuit somewhere in the sensor's wiring harness.
I would investigate the sensor's connector first for bent, corroded, loose or spread pins then the harness itself for electrical shorts or opens.

Since this appears to be somewhat intermittent there's a 50/50 chance it a connector or harness issue but be prepared for the worst if its the camshaft reluctor.
 

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Discussion Starter · #4 ·
You need to get this sorted out ASAP as this could eventually damage the engine.
Other than the sensor being defective it could also be the reluctor on the camshaft itself that the sensor works with or hopefully a connector issue, an open circuit or short circuit somewhere in the sensor's wiring harness.
I would investigate the sensor's connector first for bent, corroded, loose or spread pins then the harness itself for electrical shorts or opens.

Since this appears to be somewhat intermittent there's a 50/50 chance it a connector or harness issue but be prepared for the worst if its the camshaft reluctor.
Gross. I just put $1300 into the engine to get the oil cooler replaced. I'd hate to have to throw any more serious money at it if it's the reluctor.

If it is the reluctor though, what kind of cost are we looking at here? The vehicle only has 90k miles on it.
 

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Discussion Starter · #6 ·
OK I think I'm making a little bit of progress here, but need someone to verify.

I watched This YouTube video to get an idea of how to test the wiring harness. It's a 4 pin harness, which is different from the 2 and 3 pin harness he shows in the video, but it works just the same.

I was able to find the power wire, which is being supplied a constant 5 volts. I then turned my multimeter to the tone setting like he does in the video. It displays #'s on the display by default (185. Not sure what that means) When I probed into the other harness slots, none of them gave a tone, but a couple of them increased the # displayed on the multimeter to 388. Again, not sure what that means. But it's my understanding that by having the multimeter set on that sound/tone setting, it should give a solid beep if the ground is properly grounded, correct?

So by me not getting a solid tone, I'm assuming that means I have a grounding issue with the harness? Either that, or I need a different multimeter to test further.
 

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I've used dozens of different kinds of multimeters over the past decades.
From cheap ones all the way to expensive lab models and i got to be honest never seen a # symbol displayed on any of them that i can remember.
Are you using the symbol #'s to mean numbers?
What kind of multi meter are you using?
I assume you're trying to check voltages, Ohm resistances and grounds that should be present on the connector's pins?

You really need to dig up a pin definition of the connector you're testing.
Maybe someone here has one and is willing to share.

If you are using the tone continuity setting on the multimeter there needs to be NO voltage on the wires or pins you're testing, the wire ideally should be isolated from the rest of the electrical system with the exception of testing for a ground.

Depending on the multimeter in the tone continuity setting, the numbers 'could' be Ohms which should be at or near zero when testing the continuity of a good wire, pin or a ground check.
Not sure whats going on with your multimeter's tone continuity setting, what your really trying to test for, your multi meter has problems or whether there's some kind of pilot error involved.

Instead of using the tone continuity setting to test a wire or pin's continuity or ground, try setting the multimeter to Ohms on the lowest Ohm scale but first make absolutely sure there is no voltage on the pin or wire you're testing or it could toast the multi meter.
Before making any kind of resistance Ohm check always test the meter first by touching both probes together.
You should get zero ohms or close to it.
If testing a wire's continuity make sure the wire has no voltage on it first.
If the wire is good the multimeter should read zero Ohms or real close to zero.

To see if the wire or pin is shorted to ground, with the same Ohms setting put one of the multmeter's probes on ground and the other on the wire or pin. If you get either an over scale, very high resistance Ohm number or an infinite Ohms reading its an open circuit or possibly reading the resistance of the electrical system's back circuitry.
If you get 0 Ohms or close to it that means the wire or pin is grounded.

When ever checking harnesses for opens or shorts i always start out eyeballing the connectors very carefully first.
Connectors are one of the weak links in electrical systems.
If you suspect a bad ground, check all the ground terminals on the engine block, chassis and there should be a ground terminal near the PCM.
 

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Discussion Starter · #8 ·
Well I got a new multimeter today, and I tested the harness again. I was unable to find a pinout anywhere online for a 4 pin harness (seems like everything online is only for 2 or 3 pin harnesses), but I'm pretty sure that the ground is pin 2.

Pin 1: 1.1 Ohms
Pin 2: 0 Ohms
Pin 3: Power pin
Pin 4: 1.1 Ohms

So I no longer believe I have a short anywhere in the wiring. Which means it's probably something more severe.

I had 6 consecutive starts today, all were 100% fine.

The 7th start resulted in the rattling sound again, and the check engine light. I cleared the code, and it started fine the remaining 4 times I started the vehicle today.

I'm stumped. You'd think that if it was some kind of reluctor wheel issue, it would happen on every startup. Likewise if it was some kind of loose timing chain issue.

I'll more than likely have to take it in again to have a shop look over it.
 

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Looks like that original multimeter might of had a problem.

Interesting the connector is a 4 pin.
Basically all thats needed is a 3 pin connector;
+5v,
ground,
and the hall effect output (referenced internally in the sensor to +5V or grnd)
(I'm assuming the cam sensor uses a hall effect device.)

Guessing the hall effect sensor's 2 outputs are 'isolated' from ground or +5V all the way to the PCM where the sensor's output signal is processed. Maybe for noise immunity purposes. Pins 1 and 4 would be my guess based on your measurements.
Then it would be a 4 pin connector.

You replaced the sensor with an OEM part, seem to have confirmed there's 5 volts on one pin and a ground on another pin so its either;
a DOA new sensor (it can happen),
PCM connector issue,
sensor connector issue,
wire harness from sensor to the PCM issue,
or
a flaky reluctor wheel.

Are you positive there are no spread, bent, burnt or corroded pins in the sensor connector?

Without a connector pinout definition with ohmic and voltage troubleshooting data and an oscilloscope to check the hall effect's output signal that leaves only IMO a few DIY options before taking it to a shop.
In this order:
1. Try another sensor maybe a cheap 3rd party one that you could return.

2. Locate the harness all the way to the PCM and visually check for any signs of impingement, burnt wires, etc.

3. Remove the PCM connectors then reseat them. (Important! Disconnect the battery first and wait a while).
With the PCM connectors removed check for spread pins or any other suspicious things.

4. Find the pinout for the PCM connectors which might be a little easier then the sensor pinout.
With the PCM connectors removed check the continuity of each of the sensor wires from the sensor connector to the PCM connector and also if any of them are shorted to ground especially the wires that go to pins 1 and 4.

Myself i would not start or drive the vehicle needlessly until the problem is resolved or risk a severely damaged engine.
 

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Discussion Starter · #10 ·
Best I could find online for a pinout connector was THIS. It's for a 3.6 L Jeep engine, but I believe it was for a 2008 Gladiator or something? I can't imagine Jeep would use different 4 pin connectors across their vehicles though, so this has to be it.

I got the Pin #'s in the wrong order, but the idea is the same.

Pins 1 and 4 are the signal wires.

Pin 2 is the 5V power, and Pin 3 is the ground.

It's difficult to track down where this harness runs to, since it resides behind the engine. I know where the PCM is, but I'm unsure of how to verify which block on the PCM goes to this harness.

The harness is the female end (sensor has male pins) so I don't believe there are any kind of bent pins. The harness looks fine to me. It's possible there is some kind of corrosion inside, idk, it's so small and the holes for the pins are so tiny that it is hard to see inside.

Unfortunately, this is my only vehicle, so I'm kind of stuck driving it as needed. Luckily though, I work from home, so my travel is limited.
 

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Check the harness's female connector pins very carefully even with a magnifying glass to see if any of them are spread, burnt or corroded.
It doesn't take much of a spread or burnt pin to cause intermittent or permanent problems.
Been there, seen that, repaired that.

Since this appears to be somewhat of an intermittent problem its important to eliminate the connector as the culprit which should of been the first thing checked. Which i mentioned in my first post in this thread.

While the engine is running you could also try wiggling that connector to see if affects the engine but i wouldn't do it for long.
Same with the sensor harness where you can see it.

I learned a long long time ago to have at least one backup vehicle even if its a beater.
 
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Discussion Starter · #12 ·
I'll have to purchase a magnifying glass on Amazon later.

In the mean time, do you think some dielectric grease would help? Not sure if that is a good idea to do, but I feel like it would help rule out that the pins aren't making good connection?
 

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NO!
Dielectric grease will not cure spread, corroded or burnt pins period!
In fact make it could make matters worse far as pin to pin electrical conductivity.

I have a love hate relationship with dielectric grease used in connectors.
'Dielectric' in the electronics world means electrical insulator.

Why would factories add dielectric grease which is an electrical insulator to a connector's male and female pins be beneficial?
The reasoning is that with good brand new springy female connector contacts pins that make a 0 ohm electrical connection to the male pin, the grease will have a minimal to non existent effect on connector pin to pin conductivity.
The main reason its added to connectors is to prevent moisture from seeping in the connector which can corrode connector pins.

When trouble shooting old connectors i never apply dielectric grease to the contact pins themselves but around the connector's plastic mating pieces to prevent moisture seepage into the pin contact area.
So far that has worked for me.

Look, i'm not saying the connector is 'the' issue but it does need to be eliminated as such in the course of trouble shooting 101.

By the way, I can't believe you don't have a magnifying glass laying around.
You must be 19 yrs. old with good eyesight. lol
 
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Discussion Starter · #14 ·
OK, no grease haha.

I did an inspection of the harness this afternoon, and couldn't see anything wrong w the female ends. Looked clean to me. I do have a magnifying glass w a light coming tmw tho, so I'll check again.

That said, I drove 4 times today, all relatively short trips. Every single start was 100% fine.

It's gotta be some kind of wiring issue if it's this intermittent. Nothing else makes sense imo. If it was a legitimate mechanical issue, it would happen on every start you'd think.

Also, I'm 35 with piss poor eyesight!
 

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Also, I'm 35 with piss poor eyesight!
Welcome to the club as i'm farsighted and can't see close up things for crap.

I'm assuming the cam sensor uses a hall effect device to detect the magnetic field of the reluctor wheel.
That might or might not be true as there are other methods out there to detect the cam phase.
If it is a hall effect device it depends on the magnetic field of the reluctor wheel to produce a strong pulse signal that the PCM can use. If the reluctor wheel's magnetic field is weak then the sensor could produce no pulses or distorted pulses.
This would be the worse case scenario.

Since this seems to be intermittent, i think you might be right in that there's a 50/50 chance its connector or harness related.
If you were to bring it to a decent shop they would look at the sensor's pulse output with an oscilloscope to verify if the sensor is outputting good, bad or distorted pulses.

One other thing, have you scanned the PCM for any other CEL trouble codes?
I believe the PCM compares the cam phase with the Crank Shaft Position sensor's output.

As an aside my old now long gone Dodge Neon had a similar CEL.
Changed the cam sensor and all was good for ever after.
It had a very complicated magnetic reluctor which if bad woulda been a PITA to replace.
 
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Discussion Starter · #16 ·
I have scanned, and there are no other codes whatsoever. Just the P0340, that thankfully didn't show up at all today.

I'll report back when I look closer at the harness w the magnifying glass. Though, since it behaved so well today, I'm not going to disconnect the harness again until it drops the code again. Knock on wood!
 

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I really sounds like you have intermittent connections where one or more crimped-on contacts have worked themselves loose in the connector.

In effect, you wiggle it then it works a few times then it fails again.

You might be able to get some tie-wraps and rig the connector to have tension on it a certain way to troubleshoot it.

You could check with Jeep to see if they offer some kind of connector rebuild kit.

Even auto part stores have stuff like that.

If its a loose crimp, the wire could possibly be soldered to the contact.
If you do that, make sure you clean away the solder flux before reassembly.
And use a quality temperature controlled soldering iron, like a Weller TC201/TC202 setup.
Electronic rosin core solder, like Kester, not acid core !

Another option might be to buy that section of the wiring harness at a U-pull-it.
See if you can buy both sides for 20 bucks, and have a spare.
Splice and solder it on then use heat-shrink tubing to insulate.

Good luck, keep us posted !
 

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I have scanned, and there are no other codes whatsoever. Just the P0340, that thankfully didn't show up at all today.

I'll report back when I look closer at the harness w the magnifying glass. Though, since it behaved so well today, I'm not going to disconnect the harness again until it drops the code again. Knock on wood!
Unless its some kind of magical wood you're knocking on....I can just about guarantee sooner or later that CEL will come back to haunt you again.
And it could go out permanently leaving you stranded on the roadside....Murphy's Law.

Something like this would drive me crazier than i already am hoping it won't happen again and always waiting watching for that CEL to pop up again.

Have you at least tried wiggling the connector with engine running as i suggested earlier?
Or tried some of the other things i suggested?

If you verify the connector is 100% ok and it happens again my advice would be to take it to a trusted shop and let them diagnose the problem.
 
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Discussion Starter · #19 ·
So, I'm not sure if I found something, but I may have. Check this out.

I have the pins labeled 4-1. Pin 4 is actually sensor 1, and Pin 1 is sensor 2.

Well, the code I've been getting is P0340- Bank 1 Sensor 1. Aka, Pin 4. Well, take a look at Pin 4 on the harness. That horizontal black plastic piece appears to be broken. That piece appears to be some kind of stabilizer for the pin to seat into the female end.

So, I THINK I found the culprit. I'm not 100% sure, but it would make sense with all of the issues. Now, I just gotta figure out how to replace that harness, or the end at the very least.

Motor vehicle Automotive tire Automotive lighting Hood Automotive design
 

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Based on the pic, not sure but pin 1 does look to be spread but it could be a photographic optical delusion.

Only way to find out is cut off the old connector then buy a pig tail replacement connector at most auto part stores and splice it into the harness wires. Done.
No need to buy the entire harness but the only caveat is how skilled are you with splicing wires?
If you attempt this and need a refresher on wire splicing 101 let me know or research wire splicing on Utube.
 
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