I have a 2001 1500 3.9L with ignition issues. Last July, drove 200 miles out of town and around all day, then on the way home, it died out on the highway and wouldn't start back up. After being towed home, with codes for misfires only, (and as I'd had multiple experiences with ignition modules on a GM engine, I was familiar with the way everything just cuts out all at once and won't start back up, and the CPS and camshaft sensor are essentially the equivalents to the ICM in the GM) so I replaced the crankshaft position sensor, pickup coil (camshaft sensor), ignition coil, plugs and cap & rotor for good measure. Problem solved.



Until...

two days ago, driving home from wally world, it dies out, just cut out in the middle of driving, just like before. It's getting fuel, you can hear the fuel pump working, and there are RPMs when cranking, so I assumed that the CPS wouldn't be bad after just one year, but then the code reader picked up P0340 for camshaft position sensor - so even though it was only a year old, I replaced the pickup coil again. Still cranks, still won't start....

SO...I'm not sure what to try next...realistically, I know that any or all of the parts could be defective, even the brand new replacement pickup coil, but how often do the crankshaft sensors go out? Could it give the P0340 code? Would ignition coil, just over a year old, go bad and cause sudden engine die out and no start condition? I've heard the crankshaft sensors are notoriously problematic in these vehicles...

Is there a way to test to determine if it's a CPS problem, a PCM problem, or something else?

Help please...

 

I will give you my experience and I'll try to help you. The ignition coils unless MDS or OEM are junk in my experience. Now is it getting spark?

 

You need to determine if you are getting power(12V+)at the coil and a signal from the pcm to fire the coil. If you do then it could be the coil. There is a way to test the coil with a meter but don't remember what it's supposed to read.

 

Thanks guys. There is spark at the coil tower, and through the wire to the distributor cap. VERY weak spark at #4 cylinder, NONE at #2 - haven't tested the rest bc the battery is running down
(Incidentally, it's a brand new battery, replaced just last weekend)

As mentioned before, I just (yesterday) replaced the pickup coil, and I don't see anything in particular wrong with cap and rotor - no burns, significant deposits, no corrosion, etc. Does this seem like a defective pickup, could it be the distributor itself, or someone mentioned timing belt?

 

The pickup coil in the distributor has nothing to do with ignition. It serves to tell the computer which INJECTOR to fire.

If you have good spark from the coil, then the problem has to be after that. How old are the wires? Last time cap/rotor were replaced?

 

Uh, that's not what everything else I've read and heard says...the pick up coil in the distributor is the same thing as the Camshaft sensor in these vehicles. Cap rotor and wires were replaced last July but Im replacing again. If that isn't it, then the pickup I just put in is apparently defective...

 

Right. Pickup coil is the cam position sensor. It changes state to let the computer know 1 or 6 is in firing position. The computer uses that information, along with the crank sensor, to determine which injector to fire. It doesn't have anything to do with spark at all.

Think I would try just swapping out the cap and rotor, provided you are getting good spark from the coil, and see if that doesn't change anything.

 

But with no input from the cam sensor on initial start it will have no spark, So yes it does have something to do with ignition but not directly. Pcm needs inputs from both cam and crank sensors. It will not fire the coil or injectors until the crank shaft makes one complete rotation on initial start up. What plugs are you using? All you need is plain copper ones(autolites ). Also when you get a cap make sure you ask for "OEM style"(brass inserts)! If you don't they will give you the cheaper one with aluminum inserts that will corrode in no time.

 

WELL IT'S FIXED!!

So...thanks everyone for your help...what the problem ended up being was an isty bitsy teeney weeny (yellow polka dot bikini) No really..

the problem was a teeny tiny crack in the distributor cap around the circumference of the #1 cylinder post, where the metal met the plastic - barely visible , but once it was replaced, she started right up!

I replaced everything else - plugs, wires, etc - for good measure.