02 3.7L P0340 issue confounds me

[thewhitesparks]

Hey everyone!
First off, yes, I searched but didn't quite find the answer.
I recently bought an 02 Liberty Sport with 3.7L and manual trans. When I bought it the guy told me the check engine light was for a leaky gas cap. Not my best decision but I really like the Jeep and it sure is nice to have a stick shift after a few years of having automatics.

After finding out the code, I picked up a duralast sensor. She was running a little rough and thought this would be simple. Did the swap and it wouldn't run. She'd start but stall out quick. Pouring over the FSM, I discover the PCM won't allow the engine to run if it doesn't receive good signals from a few sensors including the CMP. I thought bad sensor, swapped for another duralast, same problem. So I swapped back the old sensor and she started and ran for another week.

Read aftermarket sensors don't do well. Got a Mopar sensor (56041584AF) and they looked identical with the exception of the numbers on the metal face of the sensor. Did the swap, same problem as the duralast sensors.
:favorites68: arty52: Okay, maybe I missed something in the FSM or online? Maybe this whole issue is the CKP? Honestly I'm lost. I'm just a guy, trying to treat his Jeep nice and make her purr. Is that too much to ask?

Thank you for any help at all.

 

[tjkj2002]

Buying the correct sensor? There is a difference between '02's and the newer years.


Also the PCM can be "dumb" with the cam and crank sensors so you could have a bad cam sensor instead of crank sensor.You really need a scope to actually see what 1 is actually messing up.

 

[Dizzydevil]

Try a compression test on your cylinders a friend of mine had that code pop up on his with same issue put new sensor in and still nothing.We talked with a a tech down at the Jeep dealership we know and suggested we check the heads for a crack and do a compression test in which we found the number 6 cylinder was leaking and the head gasket was cracked in that general area. Good luck hope that helps.

 

[ltd02]

CKP sensor will do that too but what you describe with the new Mopar CMP sensor is weird. You sure the new Mopar one was the right one? Best to get a scan on it when it's acting flaky and see what the sensors are seeing. You could swap the CKP sensor for the heck of it. Not all that pricey but may be a waste. You sure the connector is clean and solid?

Dang, I type too slow.

 

[thewhitesparks]

Buying the correct sensor? There is a difference between '02's and the newer years.


Also the PCM can be "dumb" with the cam and crank sensors so you could have a bad cam sensor instead of crank sensor.You really need a scope to actually see what 1 is actually messing up.

I hope I got the right sensor. The part number is there if anyone know what the right part number is. I'll have access to a scope next weekend and be able to get more info then.

I've got the old sensor that threw the code installed now and she'll start, just a little rough and threw the code. With the new sensor in, she'll start, but then stall out seconds later as if the PCM is getting bad signals. Hopefully probing will give me more info.

 

[ltd02]

I hope I got the right sensor. The part number is there if anyone know what the right part number is. I'll have access to a scope next weekend and be able to get more info then.

I've got the old sensor that threw the code installed now and she'll start, just a little rough and threw the code. With the new sensor in, she'll start, but then stall out seconds later as if the PCM is getting bad signals. Hopefully probing will give me more info.

That should be the correct part number for the CMP sensor. I checked multiple sources and that's the only number I could find.

Keep us posted. arty52:

 

[thewhitesparks]

Update: The community garage I would use doesn't have a scope. Anyone have any suggestions on cheap models or places to rent one?

 

[tjkj2002]

Update: The community garage I would use doesn't have a scope. Anyone have any suggestions on cheap models or places to rent one?

None are cheap,you can find cheaper 1 channel scopes from AESwave for about $400 but a good multi channel scope will run you several thousand dollars.Could not tell you where you could rent one,maybe someone that has a higher end scanner with a scope built in it could help.

 

[thewhitesparks]

Hey All,

Quick update on this issue.

Replaced the crank sensor with a Mopar and started getting misfire codes, no cam or crank sensor codes. Sweet I fixed it. Swapped coils between a good cylinder and a misfiring one. Took it down the street for some gas and to see if misfire would follow the coil or not.
Popped a 1391 and stalled out at a light. Crank but no start. Finally admitted defeat and had it towed to a dealership. Come to find out the tone wheel on my camshaft is bent. Mechanic is trying to tweak it back in place to get it running again. price difference was $3k between the bend vs replace. I know bent metal is a ticking time bomb so I'm considering replacing the passenger camshaft on my own once I can put her up in my own garage.

 

[ltd02]

Should just be able to change the tone ring. No need to replace cam unless it is FUBAR too. Just remove sprocket from cam. Try to get the FSM. there is a procedure in there where you don't even have to remove the TC cover if you wedge the secondary chain and remove the sprocket.

 

[thewhitesparks]

Should just be able to change the tone ring. No need to replace cam unless it is FUBAR too. Just remove sprocket from cam. Try to get the FSM. there is a procedure in there where you don't even have to remove the TC cover if you wedge the secondary chain and remove the sprocket.

ltd02, that sounds much better price-wise than replacing the whole cam. I have been pouring over the FSM and have not found the procedure you're mentioning. It could be that I am not looking in the correct section or item name.

Tone ring, Tone wheel, Timing cam sprocket... Seems like the more I dig into this the more names for the part I find. For reference and for those as lost in the sauce as I was prior to research the pictures below should help:

Part: Timing gear/sprocket at O'Reilly $40-$70

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Timing chain diagram

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Camshaft position sensor and tone wheel

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Thank you for all the help. Trying to treat her right, but she's more like a high school prom queen, high maintenance but fun to ride

 

[ltd02]

Try the Cam replacement section. I think it would be the same procedure as replacing the cam but you'd stop at the removal of the sprocket to get the secondary chain off. Then put on a new sprocket with a true tone ring or swap a new tone ring onto your old sprocket. I think I remember seeing a torque spec in there somewhere for the screws that secure the ring to the sprocket.

Just remember you need to wedge the chain against the guides so the tensioner doesn't relax. If it relaxes then you have to pull the timing cover to reset the tensioner.

 

[thewhitesparks]

Final update. I got my Jeep back! Had it towed two weeks ago to another mechanic for a second opinion before I wrote her off as too expensive to repair. The guys over at Brothers Jeep repair in OKC/Midwest City know what they're doing. He diagonsed it slipping timing chain before I took it in. One of the chain tensioners loosed up to the point where I slipped a couple of links. He replaced my chain guides, the parts that were missing from the dealership (David Stanely in MWC), and replaced my leaking radiator for $1600. Overall I'm quite happy with the work and result. Now to think about mods and upgrades! Thank you everyone for your support and hopefully this log helps someone in the future.