2000 dodge caravan 3.0 has code# po1391 . replaced cam sensor in distributor.still have code 1391.is it possible that this engine could have cracked flywheel like in the 3.3 engine?

Here's a link to your crankshaft position sensor. Repair Guides Cits on the bottom of the engine block, there is a heat shield covering it, thats why you can't find it, its around the intake manifoldomponents Systems Crankshaft Position Sensor AutoZone com

,1391 is the camshaft position sensor if you have a 2.5 or 3.0 engine
this is a distributor code ..just change the distributor and put new plugs and wires on the car also ( you must have over 120k on the engine )
you can get it at any auto parts store its about $200 i did see them on e-bay and bought 1 and it only lasted about 9 mo.
no savings because of only 90 day return .
all part stores give a life time return . 2x the work and I was out $125.
be smart you get what you pay for and the job takes about 3 hours if your a good parts changer. now you will have to reset all old codes with a obd tester checker. if you do not have one now get that on e-bay ( the cheapest one will work ) $ 35.

You could've gotten dirt or grease inside the cam sensor connection. They are real fussy.

http://dodgeforum.com/forum/2nd-gen-ram-tech/112989-the-infamous-p1391.html go to this web page. it has a discussion on this trouble code.

You may need a shop manual for this one.
Code 1391 means the crank sensor or cam sensor signal is not steady or dead at times.
The distributor acts as the cam sensor, so it could be that or the crank sensor, or a problem with the wiring harness.

The 1391 most likely is the cam sensor or crank sensor, crank sens is located in the bell housing on the pass side and I believe the cam sensor is in the distributor, 740 is a TCC (Torque Convertor Control) performance code. The crankshaft sensor is my 1st choice, TCC performance is calculated comparing engine speed to vehicle speed.

Are you saying the engine will not crank, or crank but will not start ?
None of the engine sensors come into play until after the engine is cranking.
Cranking problems can include the neutral safety switch and other factors with the crank circuit back to the key switch.

1391 is a timing code cam or crank sensor
0134 bank 1 sensor 1 usually left front but double check
1684 doesn't match anything i know

The code 1391 is : Intermittent loss of CMP or CKP

You are losing either the cam or crank sensor intermittently. Test and replace as needed. Check plug ends first.

You always need to check the wiring system when you get a code and not just throw parts at it,I'm sorry this happened to you.