Crank sensor problems

Perfikt

Ok, so, I've been having a problem with my used 2010 since day two (see here for the old thread...)

Short version: car had check engine, vdc, and slip lights on when headed to work, wouldn't start at all on lunch, towed to mechanic (not a dealer, but mechanic we have used before) and they ended up changing crank position sensor. Car started, but once it warmed up and they tried to start it again, no dice. They unplugged the crank sensor, it starts on 2nd try. (every time) Mechanic said a car isn't supposed to even start if that sensor is unplugged... But that is the only way the car runs, and even then,, it stays in limp mode and won't get above 3200-3500 rpm.

I need some help on what to try to do to fix it at this point, or what may be causing this. The mechanic suggested either the computer tune is bad, or the actual computer itself.

DIGItonium

Crank versus Cam sensor?

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SouthArk370Z

Get an OBD scanner and check the DTC(s). Modern cars are very good at diagnosing themselves. If you are certain that the sensor was replaced with a known good part and the car is still throwing a sensor DTC, then I'd look at the wiring between the sensor and ECU.

Edit: It could be a problem with whatever the Crank Position Sensor looks at. Some kind of cog wheel? Very low on my list of possibilities.

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Perfikt

The shop put a brand new crank sensor in it. It starts when not plugged in, so of course it has a check engine for that.

fuct

for $250 the dealership can do a complete diagnostic test. takes 4 hours.

SouthArk370Z

Are there any other DTCs showing up?

I haven't read the manual on that circuit but am a little surprised it will start with the sensor unplugged. Apparently the car thinks it can run in limp mode without doing too much damage. The fact that it won't start with the sensor plugged in leads me to believe the connector may be causing the problem (or the sensor is bad).

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Perfikt

Apparently my mom got tired of the car problems and made an appointment at the Nissan dealer to look at it.

Video of what it does when sensor is plugged in:
video

DIGItonium

Issue looks and sounds familiar to owners who ended up getting new fuel injectors. Basically the car is hard to start after warming up.

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Perfikt

my issue has nothing to do with warming up. every time, regardless of how long it has been running previously, crank sensor plugged in, nothing (see video above). unplug sensor, starts second try. it works like that even for the first start of the day.

Perfikt

Brought the car to the dealer, and they were no help at all. They seen the wiring harness had been modified to accommodate the lambo doors, stopped right there and didn't even look at the problem I brought it in for. So I got it back from them and started playing with the car myself.

I got it to start, with the crank position sensor plugged in, but it would always be in limp mode and take a few tries to get running . so i limped my Butt over to auto zone to read the check engine codes. It had several and all of them mentioned cam position sensor, bank 1, or timing off. So when I get back home, I unscrewed the cam sensor on the passenger side, and rotated it about 30 degrees. Car starts flawlessly every time, first shot, no hiccups. I ran out of light before I got a chance to reset the computer and see if it goes limp mode with cam sensor rotated or not.

Anyone have a possible explanation for why it would start so easy with cam sensor rotated?

SouthArk370Z

Why did you choose 30 degrees?

I can't imagine what the door wiring would have to do with either sensor. And it really blows my mind that you could twist the cam position sensor 30 degrees and not throw a DTC or three.

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Perfikt

i didn't understand the door wiring either. but my brother suggested it, and to both of our surprise, it worked like a charm. we even played with it and tried to see how little you had to turn it before it would start with that sensor actually plugged in, and it had to be turned about 25-30 degrees clockwise, or unplugged. otherwise, car wouldn't start. and it wouldnt throw any codes, or at least didnt have the light on. but we never reset the computer to get it out of limp mode and see if it would even go into limp mode with the sensor turned. (was in limp already from testing random stuff and trying to figure this stuff out)

juld0zer

thats really bizarre because the way the sensor is designed, it can only be secured in one position give or take a few degrees at most. and im
willing to bet that the tip of the sensor will produce the same signal irrespective of whether it is bolted in the intended position or glued in place rotated X degrees from the bolt hole

Bobbyredz

Do u get ur car to run yet ?

DYNAZOR

My first guess is that the wire carrying the crank sensor signal is shorted (either a full short or partial short) to another wire going to the engine controller (not shorted to ground or to a voltage source), and the crank signal during cranking is distorting the signal being carried on that other wire. The Z apparently allows starting and running in "limp home" mode without a valid crank position sensor signal present, as evidenced by the conditions you describe. In my theory, if the crank signal is indeed distorting that other signal, the engine controller is too confused to be able to allow any ignition to occur (high possibility of engine/catalytic converter damage). Just my 2 cents.