bobpat

well first tow home tonight on way to work. cruising along at 55 no problems. heard a "thunk" and engine light on engine died. pulled over put in park restarted fired right up.. for a sec or 2 than idle dropped to about 100 and died. anyway grandson grabbed the trailer and came and drug me home. put reader on it got thep0340 po353,352,351 and p1391. did some reading in here seems p0340 is a common problem . my question is most say cps replacement but is cps crank position or cam position? seems like they mean crank position? most often, and i have a 2009 xj so no distributer where is the cam position sensor on mine? is in the hole the distributer would be in? the other question is having read thru alot of p0340 code write ups no ones mentioned a loud noise or thunk with it?? Any info would be great.

Firestorm500

Did you throw a rod?

How is your XJ a 2009?

bobpat

lol ok the xj is a 2000 fat fingered the 9 sorry, no don't believe there's any damage at this time the jeep will start most of the time right now and run fine for about 30 to 45 secs (which it wouldn't do if it threw a rod ) than makes the thunk noise ,which after watching a youtube video on crank sensors i now believe the thunk/noise is a massive misfire/backfire before the engine dies. will look at crank sensor this weekend looks to be pointing at that for now

Firestorm500

You need to start looking around for a cracked head, coolant in the oil or the cylinder(s).

bobpat

have a sensor in hand also picked up oil for oil change will know better after I get that all done. Is there a good source for sensors other than dealer, mopar senor that is. I have a unit from autozone to see if that is the problem but want to get a oem on its way and put it in when it it arrives, I will just keep the autozone around for emergency I guess.

51 ashton

Save the oil until after you've determined the head is cracked. I did just as your going to do on Christmas day only to find out I wasted money on the oil/filter due to a cracked head

bobpat

well no sign of head crack, oil clean, no floating oil slicks in anti- freeze, replaced crank sensor with oreillys part no help, replaced cam sensor no help, have mopar for both on the way. put fuel pressure gauge on rail 40 psi. I did notice on the cam sensor that the position of the sensor and the harness has it laying against the block hard against it actually. videos i have watched show there harnesses 90 deg pointing aft. might set tdc and reset the shaft in hole?? does not seem right that is against the block like that. other than that at a loss unless I got a bad sensor from orielly's. any thoughts ? thanks

tjwalker

The P1391 can be either cam or crank sensor (most often crank sensor when it is the only code) but the P0340 is no cam sensor signal. I wouldn't give up quite yet on that clue.

Search for CAM SENSOR INDEXING and try that. It can be quite important especially with the 00-01. Shouldn't take you long to find the procedure.

Good luck and keep us updated!

bobpat

thanks for the reply I am still going thru the search results for CAM SENSOR INDEXING. so far lots talk about doing it but not how to do it, seems theres something about holes in the side and a toothpick but step by step yet

HappyTrails

If you have to replace the crank sensor, and it is like my 96, way up on the bell housing barely reachable between the intake manifold and the firewall, then read up on the techniques of how to do it. There are lots of wrong and time consuming ways. And there is at least one easy way that only takes a few minutes.

Here is what I posted before:

Do all the wrenching from under the vehicle. Use about 42 inches of extension.

Basic rule of changing the CKS is remove the TOP bolt first. No opening yet for it to fall into. Bottom bolt is below the opening. Then with the new CKS install the BOTTOM bolt first. You will be working below the opening. Then the top bolt. That way gravity will not betray you to an opening in the bell housing and suck in a bolt. Which creates a whole other headache.

The job was a piece of cake on my 96 XJ. On installation I placed the new CKS into the bell housing from above (tight but doable) and I did the bolting from below with about 42 inches of ratchet extension and a wobble joint up on the socket. I taped each bolt to the socket for installation so as not to have them drop out somewhere. And I put some tape around the wobble joint to keep it from flopping over too much.

From under the vehicle one hand was up high to guide the extension/socket assy. The other hand was down and back by the exhaust pipe to operate the ratchet.

Stop by Harbor Fright or other source to get the needed extensions. The few bucks are worth the time and hassle savings.

I was getting similar codes, so I replaced both Cam (CPS) and Crank (CKS) sensors. On the 96 the CPS is in the distributor. Same location on the engine as 2000 CPS. Indexing is same in principle, but specific to the hardware. And critically important to get right. Not difficult with the right instructions.

Since both sensors feed interacting data to the computer, I figured replacing both was good since they were old. Codes went away and we have been in happy land.

bobpat

Well here's an update, started the cam position sensor indexing task.. pulled the syncro shaft (the part that goes into the block ) it had seized up solid and tore half the teeth of the shaft, so dropped the oil pan and inspected the cam and everything else down there cam drive gear showed no damage at all I was amazed. anyway so as it stands now the jeep is running great with new crank sensor, cam sensor. found most the big pieces of the broke teeth down in oil pan ,so I paln to run this new oil and filter for a week than drop oil pan again and look it all over again and ho from there. Side note I read almost every thread I could search on this problem when it first happened and I didn't see any one say they had this happen. That syncro was locked up tho even in a vise with a monkey wrench it would not budge. iol pressure was normal at time this happened, and oil pressure is at 6o psi cold and about40 at idle hot so I am at a loss for the why. thanks all for the reply's.

bobpat

further update; been driving every day since the repair and oil change, running great no problems at this time will run it the rest of this week and do another oil change, and call it good.

HappyTrails

Thanks for the report. You made it sound so simple to fix. But we know it was a lot of careful work.

But the broken piece does make one wonder what happened. Defective item? Maintenance failure years ago? Some other piece got caught in the gear? No one will ever know probably.

bobpat

yea i'm with you no idea why it went and I searched a lot of forums, websites ect not once did I see a seized shaft( still not sure of the name syncro?? shaft) any who I feel like im as set as I can be on it so I installed my new 4 hole injectors and throttle body spacer yesterday it sure runs nice, but it was a nice running engine anyways up tp that point. Thanks for the replys.