P0340 - fishing for ideas

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hoppy

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Greetings,

05 Liberty L4, 160Kmiles.

Pulling my hair out over this one.

So the P0340 code year ago or so, took to shop, fixed for awhile (replace Cam PS and clean everything in sight).

Recurred. They replaced Cam PS again, about the same outcome.

Was able to drive for quite a while, just tolerated that it would eventually turn off check engine light, then buck like crazy, cycle the ignition, CE back, but drivable - rinse repeat.

Went to hell a few weeks back. Got a solid misfire when under any sort of throttle load.

Decided to do some of my own swapping. Wasn't ready for the shop hassle again.

Did both Cam Sensor and Crank Sensor (basic Autozone Fodder). No joy.

Decided perhaps ECU, so sent mine off for a rebuild. It's an old girl, after all.

Get it back, same situation.

I must interject that I really "hate" the slide-ey adjustment for the Cam Sensor. The one I pulled out was rubbed raw because of misinstall.

Okm so presumably two good sensors and a rebuilt ECU. Pretty much same problem.

Little snooping, and somebody had scraped the insulation from the Cam sensor and retaped it. Regardless, a place to probe, although they had scraped ground and +5 rather than the signal wire. Fixed that, so I can see what it's doing.

Put a scope on it, and can see a square wave "most" of the time. It's like 1 in 20 misses. Should be zero, and it's really touchy around where I "slide" the sensor to. I tried to put it just shy of "rubs on the camshaft". I have no idea if this is "normal" or not.

After squaring off that, bit of test drive, and now it codes with "Crank Position Sensor" - after misbehavior. Ofc that was also changed, so I have my doubts...

Recalling back to conversations with the "shop" when this work was going on, they indicated that there was some problem with the Cam sensors, and they were trying to find the OEM part, and never succeeded. They also indicated that it was "recommended" to change Cam and Crank together because of "reasons", so If I still had the issue that was their next move.

So, fishing for ideas/information/suggestions on this. Is this really a known problem, and if so, what is the solution?

Hoping for some insight as to what to try next with this beast. I must be missing something.

It wouldn't suck to get this boy driveable again.

Thanks,
Clay
 

LibertyTC

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When it comes to sensors for the KJ, it is always best to source Mopar parts if possible.
You might want to consider another brand in parts beside Autozone...
 

hoppy

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Well, that would indeed be sage advice, if it were actually the case that such a thing could be found.

The issue is that they are discontinued, and thus unobtainium.
 

Xterra4x4

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Greetings,

05 Liberty L4, 160Kmiles.

Pulling my hair out over this one.

So the P0340 code year ago or so, took to shop, fixed for awhile (replace Cam PS and clean everything in sight).

Recurred. They replaced Cam PS again, about the same outcome.

Was able to drive for quite a while, just tolerated that it would eventually turn off check engine light, then buck like crazy, cycle the ignition, CE back, but drivable - rinse repeat.

Went to hell a few weeks back. Got a solid misfire when under any sort of throttle load.

Decided to do some of my own swapping. Wasn't ready for the shop hassle again.

Did both Cam Sensor and Crank Sensor (basic Autozone Fodder). No joy.

Decided perhaps ECU, so sent mine off for a rebuild. It's an old girl, after all.

Get it back, same situation.

I must interject that I really "hate" the slide-ey adjustment for the Cam Sensor. The one I pulled out was rubbed raw because of misinstall.

Okm so presumably two good sensors and a rebuilt ECU. Pretty much same problem.

Little snooping, and somebody had scraped the insulation from the Cam sensor and retaped it. Regardless, a place to probe, although they had scraped ground and +5 rather than the signal wire. Fixed that, so I can see what it's doing.

Put a scope on it, and can see a square wave "most" of the time. It's like 1 in 20 misses. Should be zero, and it's really touchy around where I "slide" the sensor to. I tried to put it just shy of "rubs on the camshaft". I have no idea if this is "normal" or not.

After squaring off that, bit of test drive, and now it codes with "Crank Position Sensor" - after misbehavior. Ofc that was also changed, so I have my doubts...

Recalling back to conversations with the "shop" when this work was going on, they indicated that there was some problem with the Cam sensors, and they were trying to find the OEM part, and never succeeded. They also indicated that it was "recommended" to change Cam and Crank together because of "reasons", so If I still had the issue that was their next move.

So, fishing for ideas/information/suggestions on this. Is this really a known problem, and if so, what is the solution?

Hoping for some insight as to what to try next with this beast. I must be missing something.

It wouldn't suck to get this boy driveable again.

Thanks,
Clay
I had a bad MAP sensor (sits between A/C in the front on intake manifold) was running bad spitting out different codes, good luck
 

mateorosi

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Hey Clay, sounds like a tough one. Try replacing the cam sensor with an OEM part and check wiring for damage. Good luck!
 

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