Camshaft position sensor

[qwertydog]

A couple of days ago my '03 Sport with the 3.7ltr engine stalled in a parking lot. I managed to get it restarted and got it home where I read code #P0340, which is "camshaft position sensor circuit malfunction". Well $80 later I put in a new sensor, cleared the code and the engine started up and ran perfect. For one day !!! Today it did the same thing in another parking lot and once again I got it home with the check engine light on, and it gives the same code as before. I double checked the plug on the sensor and I am sure it is clean and tight. Any thoughts on this one? Is there another connection point that might be causing this? I have not been able to buy a shop manual yet so I hope someone can steer me in the right direction. Thanks for any help.

[qwertydog]

Today I bought a Haynes manual for my Liberty. What a waste of money ! Pages and pages on how to tear down the engine, like how many diy guys do that anymore ? I was hoping for an engine management wiring schematic , but they have left that one out. Chilton manuals are much better but for some reason the stores around here have stopped selling them. I am going to try one of the "factory" dvd manuals on flea bay, only trouble is that it will take a week or so to get here. Any help on solving the sensor problem would be appreciated.

[jpb53]

try this.
http://pdftown.com/Pdf-eBook/Jeep.html?from=15

[qwertydog]

Thanks jpb53, the link worked perfectly. I now have the schematic I need to pinpoint the problem. Tomorrow evening I will be under the hood with my DVM hoping to find the cause of this mystery. I will post on what I find. Many thanks!

[jpb53]

Google is your friend.

[qwertydog]

I printed out the page with the sensor wiring and then checked for continuity on the three cam sensor wires from the sensor plug to the PCM. All three gave a perfect reading. As this is an intermittent problem I do not suspect the sensor or the PCM; these components either work or not, they rarely give this kind of erratic behavior. I did notice that the 5 volt feed and the PCM ground to sensor wires have a total of five splices in them whereas the sensor signal wire is a direct link between the pair. I am inclined to think that maybe one of the splices is causing the problem, so tomorrow I will run my own wires direct between the two. As I cannot trust it the way it is, at this point I think it is well worth a try. I will keep you posted on my progress, if it runs for a week without playing up I will give a detailed description on how I did it which may help someone else with this situation.

[qwertydog]

Today I decided to run my own wires directly from the sensor to the PCM. I disconnected the negative battery cable, removed the air filter assembly, then using a three core wire I spliced into the sensor wires close to the sensor and then ran this around the fire wall to the PCM. There I spliced into the three original sensor wires close to the plug on the PCM. I left the original wires intact, all I have done is bypass any possible bad connection or splice in the original wiring, which could be causing this problem. I used a black covered three core wire and black tie wraps, so it all looks OEM ! I have taken it out for a test drive which included stopping and starting in a couple of parking lots, and so far it is performing perfectly. I hope this is the cure, only time will tell.

[qwertydog]

So much for my bad splice theory ! My direct wiring fix lasted all of two days, today it started running rough and stalling in town, when I got it home it shows the same code - P0340. I find it hard to believe that the PCM can work fine for a day or two, then show the same code. With a new cam sensor directly wired to it what else could it be ? I will have to start phoning the wreckers to see who has got a Liberty PCM.

[javatrooper]

let us know when you get this figured out. I can't help but I'm about to pick up a Liberty so I'm very interested in your progress. good luck

[hundahunta]

replaced your crank sensor also.....

[qwertydog]

No I have not replaced the crank sensor because if that causes any problems there are several codes that apply to that sensor. The only code I am getting is for the cam sensor.

[fredjacksonsan]

An intermittent issue like this could point to a failing wire. Check the wires to be sure they're in good condition; I've seen posts on here where a wire was rubbing off the insulation around a corner and causing a devilish problem.