Nissan Repair: 02 maxima wont start, mass airflow sensor, crank sensor

Question
QUESTION: i bought an 02 maxima from a repo yard..the car hadnt been started in about 10 mnths...they couldnt figure out why the car would not start, but when i was told that the lady never turned in the key i figured it to be an immobilizer issue..no problem right?? wrong!! i had the car towed twice to two different dealers and the key and pcm programed..both times i ended up towing the car back home cause they couldnt figure out what the problem was without charging me four hours of diag!! being a tech myself i decided to investigate myself...all fuses good, i have fuel pressure to the rail and injector pulse..115 psi on all cylinders..good timing..power at the coils but no signal??? is there an external ignition control module or is it built in to the computer??? is it a good chance that the pcm is bad or could i still have an immobilizer issue?? what reasons are their that could prevent an immobilizer unit from being programmed??? would a maf sensor or any other sensors cause a crank but no start condition?? also no codes came up on a pcm diag...

ANSWER: Sergio,

I would start by making sure the crank sensor is working properly.  Get a volt ohm meter and make sure the hall effect is working.  Second, check the mass airflow sensor and just for kicks remove the ECM and check for damaged pins.  If you have access to nissantechinfo.com they have the harness diagram to follow.

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QUESTION: i will do...but if the sensor was bad wouldnt the car at least attempt to turn on?? wouldnt it go into default mode?? my interest is more along the lines of the pcm...i need to know how the coils get signal from the pcm and how to check that...i dont want to spend towing charges, buying a new pcm, and then paying an hour labor for it not to turn over again...or... if something in the immobilizer system is bad?? the dealer said everything was good in the immobilizer but i dont think theres a way to check this without the factory scan tool...

Answer
Sergio,

The vehicle immobilizer would not be the problem here since is basically cust power to the fuel pump.  Nissan uses a relay and a ground within the PCM to activate the pump.  Given the reference signal from the immobilizer and a continued response from the oil pressure sending unit.  If youi are not getting a square wave from the crank angle sensor it would not allow the coils to fire.  You stated that you get power to the coils but they are not firing.  Therefore, the problem probably lies with the crank angle sensor or the PCM itself.  The PCM is quite expensive.  But, a used one would be a good choice since ti is half the cost.  You really need a breakout box to figure out of the PCM is not getting a reference signal from the crank angle sensor or if the PCM is not switching the coils on and off.  My bet is the crank angle sensor since I have seen very few PCM failures.  Also, since you bought the car at auction I would really check out the wiring to make darn sure the wiring has not been disturbed.  People think they can hotwire a cra and really screw up things under the dash.  Be sure to check all the relays under the hood to make sure none have been remoed or replaced in the wrong place.  Also, the PCM is under the dash at the firewall end of the console.  There is a plastic plate that is covering it on the driver's side, under the dash.  Pop out the place the remove the screw and pull the handle to disconnect the harness from the PCM, disconnect the battery before you do.  Then carefully reset it to make sure the pins plug back in.  If the car has had water damage you will corrosion on the pins.  I have seen a few flood vehicles that have been cleaned up and not run.  So, that could be a possibility.  Email me back and let me know what you find.