Little background.. I have an Altima with a vq35de. Car ran perfectly fine before the built auto trans and engine went in the car, no fault codes nothing. Put the built motor and trans in the car, upgraded torque converter ect. Got it all back together, car wouldnt start for awhile, took probably 20 times cranking before it started, then it ran fine. This was two weeks ago.

Current condition - Car has extended crank, throws P0335 crankshaft position sensor code every time the car starts, after 8-9 times cranking it starts, running off the camshaft sensors. Runs fine, put the car in D, car will barely move. Put it in manual mode, trans is in limp mode and is in 5th gear. Reverse is fine, its how i have been moving the car to try and figure this problem out.

What i have done

- Replaced the crank sensor, no change. Dont see why old sensor would of gone bad either, so i know that is ok.
- checked power and ground, they are ok.
- connected a universal scope to see if the signal was being sent or if there even was a signal.. heres what it looks like.







So as you can see.. there really is no signal at all, its barely even .03V and jumps around, signal has no definition at all. Now im figuring that it is supposed to be a square wave signal.

My question is that, is the signal wire to the sensor supposed to be 12v? I have 12v to the sensor, and good ground. Anybody have any ideas whats the problem? Only things i can think of are the flexplate itself, of the gap between the flexplate and the crank sensor has changed and it is too far away, but there is no way to adjust that.

 

what do you mean extended crankshaft? do you mean a stroker crank? make sure the ring is correct the fwd cars have a different pickup ring on the flywheel/flexplate with a different spacing then the 350z. 350z is 17mm the fwd cars have 24.5 mm spacing.

 

Yes, the wires should be 12v, ground and signal. You have not made any wiring changes that could have mixed their positions up? The scope you have definitely shows no signal. If you remove the crank sensor and look in it's mounting hole, can you see the trigger wheel centered in front of it? To get a rough idea of distance to trigger, you can put a mound of playdoh on the crank sensor and test fit it.

 

@ jerryd, no its not a stroked motor, just a built short block. I meant extended crank on every start, not extended crankshaft.

Hal, ill have to check that and make sure, but im pretty sure it is centered. I dont know why it would be different from motor to motor though, its hte same short block from 02-06

 

Are you measuring the signal at the ECM or at the sensor itself? Is 12V and ground making it to the sensor?

 

measuring it right off the sensor. yes sensor has a good 12v signal and good ground. Used all the same parts from the stock motor on the built one, ill have to double check that the flexplate is lined up over the crank sensor.. but if it isnt then i have no idea why it wouldnt be. That would mean the crank was sticking further out the rear of the engine then the previous blocks was.

 

Little update. I checked to make sure the flexplate was in hte middle of the crank sensor hole, and it is. The gap looks fine, i didnt measure it, but the sensor is pretty close to the flexplate.

Connected jumper wires from the harness to the crank sensor and measured the voltage right off the sensor, now the scope shows no signal at all, has good power and ground. Im wondering if i just got a bad sensor for some reason.. although i dont know why two of them would be bad, when i know the previous one was fine before.

 

kinda interesting as long as theres power and ground the sensor should work if its good. did you happen to do the fsm resistance check? basically it just has you make sure there is continuity between pins 1 and 2, 1 and 3 and 2 and 3. it can only be a flexplate or sensor issue since you have power and ground and arnt getting any signal at the sensor. it kinda dosnt make sense if the pickup ring is in the correct place and the sensor has power and ground the only thing i could think of would be space between sensor and flexplate but that dosnt make much sense. ill think about it a bit more throughout today see if i can come up with anything.

 

yeah i think im going to try and see if unbolting the torque converter completely from the flex plate, maybe its tweaked or something, then bolt it all back together. hopefully it will remedy the problem so i dont have to drop the subframe and take it all apart again..