Okay, I've been searching for 2 days in between freezing trying to get my truck to start and still can't find an answer that really helps. Sorry for the book that follows, information is important though!

First : 2000 Dakota SLT 4.7L 4x4

Problem : No start.

History of related repairs :
I replaced the CPS about a year ago, from Napa, when I was getting a P1391.
Seemed to fix everything up.
In October when I needed an Inspection the state computer would not connect with my truck, there was a PS PSI code in the memory and some bad grounds, fixed all that and got the inspection done, everything has been great.
I was pulling my friend out of the snow last week, I live near Buffalo and we just got 7 feet of snow in 2 days. So he kept getting stuck while plowing and I was just yanking him back out of the piles. Hell of a sight my little Dakota pulling his "Big bad F250", but I was able tyo get him out all the time with very little effort, my truck has some torque!
So I was hooking up the chain the last time and my truck just shut off like someone turned off the key. I tried to restart and it would only turn over.
Went through the usual,
fuel pump running - Check
Check all major fuses - Check
Check connections for corrosion, loose - Check
Still only turns over
Forgot to check the Crank sensor, unplugged checked and plugged in, Truck starts!! Move it out of the way and it dies before I can park it on the side of the road. MIL on now, no computer with me so I called and had a Crank sensor delivered to me, and my Computer and replaced on the side of the road in the snow and crap, what fun. Took like 3 hours because of course it was seized in the block after 90,000 miles and I had limited tools with me. Got the new on in and no start just turns over. Scanned MIL and got a P0340, so I get a Cam sensor and replace that. Still no start, but now I'm getting a P1391, when I was getting that code before my truck would run, it would just miss now and again. Couldn't figure it out on the road side so I went back the next day to tow it home and decided to put the old Cam sensor in it, it started right up and made it half way home, about 5 miles before it died again on the road. So we towed it the rest of the way home. Was getting P0340 again, so I put the new Cam sensor in again and started getting the P1391 again. But every now and again my Innova scanner would loose connection with the PCM. I had left the PS PSI sensor unplugged because the new sensor started leaking, go figure, but have never gotten a code for that since October.
I Checked the wiring for continuity between sensor plug and PCM plug with both unplugged and they were good. Plugged back in PCM and checked for voltage at Sensor Plug getting 5.1V at Orange wire, good, no Volts at ground, good, but I also get 5.1V at the signal wire, either unplugged or plugged in back probing. I do not have any continuity between the signal and power wires with everything unplugged, but with it plugged in the is some sort of connection between everything, kinda figured there would be some, not a real test anyway.

Any Ideas, or should I just order the PCM?

 

P0340 is no cam signal at PCM.
P1391 is intermittent loss of cam or crank position sensor signal.

The cam and crank sensor share the 5 volts supply and sensor ground. You can lose connection to the PCM if there is a short in that circuit - it kills the 5v supply. You seem to have given the circuit a pretty good going over but check it with the CKP disconnected.

You might try swapping the CKP out too. Yes, it can be a bear on an older 4.7.

You don't need a computer to read codes on your Dakota. Just do the key dance. With the truck OFF, turn the key to RUN (don't start it.) Then turn it back to OFF, then RUN again, back to OFF, and finally leave it in RUN. Codes will display in the odometer window. It will show P DONE when finished.

 

Thanks Dan,
I didn't even realize I could do the key thing till I started searching for info, good to know though.

But I shouldn't be getting 5.1V on the signal wire at the cam plug should I weather the crank is plugged in or not, Correct?
And I've already installed a new crank sensor, or are you suggesting I do yet another?

 

No, if you've changed it once I wouldn't do it again - yet anyways.

You can't really test a crank sensor with a voltmeter. The waveform will vary as the engine is running - an oscilloscope is used. Double and triple check all connections with the CMP and CKP sensors. I've attached a schematic.

 

I've had issues with non-Mopar crank sensors on my 3.9l Last time my mechanic replaced it with Mopar and have had no issues since. He didn't charge me any labor on it since the previous sensor obviously had issues.

Just saying.

 

Lambs had a good point. That'd apply to both the CKP and CMP sensors.

 

I bought all parts at Napa, There higher quality, I think than some.
I don't really want to test the sensors while the engine is turning over. I would like to "Bench test" them. Like what two pins should have resistance and which shouldn't.
Also with both the cam and crank sensors unplugged I have 5.1V at both outside wires, the power supply and the signal wire. Both center, ground wires have no power and have continuity to the PCM plug. All other wires continuity is good from plug to plug also.
I will go get the cam sensor at the dealer, not priced bad at all, but I would rather not try another sensor if it is just going to burn out because I have positive voltage at 2 wires on the plug.
So if I knew the Ohms check for the sensor, that would help, also if I knew That both wires should have 5.1V. I didn't think the signal wire should have any power to it if it's unplugged from the sensor.

 

Dan needs to confirm this, but I THINKboth sensors are magnetic type, and will not have resistance. Should be open on their own and closed near a piece of steel?

 

Both the CKP and CMP are hall effect sensors. The output voltage changes as the tone wheel is closer or further away. An oscilloscope is the best way to test them as you can watch the voltage rise and fall. But, try this:

Cam sensor:
Unplug the sensor. Check for ground on the black/light blue wire. Turn the key on and check for voltage on the other two wires.
Plug the sensor in and probe on the violet/white wire and verify 5v.

Using a voltmeter, connect the probes on the tan with yellow tracer wire. Slowly rotate the engine by hand. The voltage should vary between 0 and 5v as you turn the engine.

Crank sensor:
With the senor unplugged check for ground on the black/light blue wire and 5 volts on the other leads.

Using your meter connect the probes to the gray with black tracer wire. Turn the engine by hand and the voltage should again vary up to 5v.

 

Thanks Dan, Thats what I was wondering, if I should have Voltage at both wires. I'm going to make sure my cam is turning and put a sensor in from the dealer when my wife picks it up later.

Another question, should I be worried about any shims? I didn't realize some of these engines and the shims on the cam sensor. Both of the Napa sensors have very light marks / scratches on the face of the pick up. I can't realy feel it on one but the other my finger nail just seems to catch on them?
I believe the date code for my engine is 1290. I'll search for that TSB again.

Thanks for the help everyone. I'll keep you posted on my results, or invite you all to the bon-fire when I torch this thing!! LOL