How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask George H. Your Own Question
George H.
George H., ASE Certified Technician
Category: Nissan
Satisfied Customers: 18699
Experience:  ASE Master 15+ years
Type Your Nissan Question Here...
George H. is online now
A new question is answered every 9 seconds

Nissan altima: the signal wheel on the crankshaft, i see there..tdc

Resolved Question:

hello i have a nissan altima 2,5s year:03/03.
my question is about the signal wheel on the crankshaft, i see there is a space on the signal wheel/tooth missing. dose the misssing tooth signal tdc for cylinder1?
Submitted: 5 years ago.
Category: Nissan
Expert:  George H. replied 5 years ago.

Hello I will help you with your question,


The computer uses the gap to calculate TDC #1 but it may mot be located there. When the engineers know where the gap is they can program the software to add or subtract rotation to calculate the position of the crankshaft and do not have to place the gap at exactly TDC. I would have to install the balancer and turn it to the mark then observe the timing reluctor to see if it is rising edge or falling edge of the gap is TDC.


Let me know how I can help you with this


Thank you



Customer: replied 5 years ago.

who is they, the dealership or the manufacturer?

if i understood correctly that the tooth marking either before or after the missing tooth.

what would happen if the crankshaft was turned 1 time? would the ignition be off/ not spark casuse of it?


Expert:  George H. replied 5 years ago.

The manufacturer, sorry for not being clear on that. The exact TDC point can be setup to use the start of the gap or the end of the gap depending on what the engineer wanted to make it.


If you are 180 out on the crank position compared to the cam it will still spark just not at the right time.


The gear causes the crank sensor to create a signal each time a tooth passes and the signal is sent to the engine computer which counts then to know when each piston is at the top of its travel and the computer will fire the coil when it determines the most power will be made in the cylinder depending on its other sensor input.


If you don't have spark you check the signal from the crank sensor to the PCM and see if it gets there. A scantool looking at RPM is a great way to do this.


IF you have RPM showing on the scan tool the computer should be signaling the coil to fire. If you have power to the coil it should fire when the computer tells it to.


The rest is mechanical having the chain connect the crank to the cam and keep them in time.


Let me know how I can help you


Thank you



Customer: replied 5 years ago.
ok, it seams that when i put the timing chains on time the sigal wheel dosen't line up on the crankshaft sensor, now this might be right cause i haven't touched the signal wheel or crankshaft. the timing is right, i didn't check the rpms before taking apart the covers but will check the rpms once everythings put back together. dose the missing tooth have to line up with the sensor? when its on time the missing tooth is 6 teeth behind or 10 teeth before the gap in the sensor wheel.
Expert:  George H. replied 5 years ago.

OK, that may be the right place I have never checked I just line the chains up as shown in the procedure.


Do you have any way to see if you have signal from the crank sensor?



George H. and 7 other Nissan Specialists are ready to help you
Customer: replied 5 years ago.

thanks forn the info, i took the timing chain covers off again reset the timing again. refitted the covers reassembled the sub-frame and started to check for the rpms, but thye engine started right up. i think what might have happened was the cams where on time but the crank was 1 tooth off/slack was on the nwrong side of the timing chain/away from the tensioner and the crankshaft mover 1tooth to pick up the slack.

apon reseting the time ans ensuring the chain was tensioned correctly i believe that fixed the problem of no spark. your help was very inforamtive and spot on. i wouldn't have bin able to fix the problem without the info you provided.

again many thanks i will be comming back when i have another problem.