I have read several threads about this and am leaning towards a bad new sensor. I just cant bring myself to replace a new sensor. The truck starts hard, idles fine, no codes until I hit the throttle, then P0336 and runs awful. It has a FASS, Edge with attitude, and show 16PSI fuel.
I have cleaned the grounds, getting 5 volts to sensor, wiring to ECM looks good and OHMs out good.
I tried checking voltage on the signal wire and never have more than .5 volts while turning the crank by hand, not sure if this actually works.
So, any ideas, or just replace the sensor?

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I have noticed that the grid heater doesn't cycle and the pump doesn't run unless I cycle the key three times. On the third cycle the pump kicks on and the wait to start light comes on and I can here the heater solenoid cycle. The truck fires right up no hard start. I still have no tach and I still have a P0336 code.

 

On question 1: The only real way to properly test a square wave sensor is with the oscilloscope. I see a couple of things to check 1st: check in the 50mv or 100mv scale the ground circuit of the sensor. 2nd: Use the oscilloscope (hopefully a 2 channel) to view the signal at the sensor maybe even at the ecm, compare the results.
Could be the sensor ring, air gap, sensor or ecm.
As for the three key turn, couldn't tell you without seeing it. That could be a faulty ignition switch, wiring, pcm or ecm.

If this leads in the direction of a computer I'd definitely check powers and grounds prior to anything replacement.


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I cleaned the plug on the vp44. Found corrosion on a pin in the plug on the firewall. Cleaned and greased those plugs. Cleaned and greased the fuel pump relay connection. The alternator went up in smoke so I replaced that. My delayed wait to start issue has gone away and the fuel pump primes now. I still had po336 so I replaced the cps again and now that problem is gone. So obviously I just have multiple bad connections and maybe a faulty new sensor.

 

I work for a John Deere dealership and from time to time you do get a bad sensor out of the box and it is super frustrating. If you can, find someone that'll allow you to do some swapnostics in the future. Might help save on the bucks.