Nissan Repair: 2002 QX4, last four digits, air control valve

Question
Hello. I know I asked you questions before about my truck. I am having a problem with the truck running too rich, also the truck revs up to 2000 rpm while in park when the engine is running.The codes I get is MAF Low Input and EVAP Pressure Sensor. So I am going back to when I replaced the ECU, I replaced it with one from an 2002 pathfinder. All the numbers matched to the old ECU, except the last four digits. So I am thinking I got the wrong ECU in there-? Any help would be great, thank you.

Answer
Anil,

If the MAF is reading low I would check the unit for proper output.  If the sensor wire has been damaged you will have problems.  If it is dirty it will read low too.  Check the book on how to check the pins and use of a volt ohm meter.

The second thing is to check the evaporative canister and the valve that actuates it along with all hoses and clamps.  If there is a leak or the valve is defective you will get that code too.

I think the ECU will work but I have never had the opportunity to switch from one to another.  Same year, same engine, same transmission it should work.  Also, check the MAP sensor and make sure the idle air control valve are operating properly.  If there is crud in the path of the idle air control valve it will screw up the idle and it will get stuck where the idle is too high or low.  Basically, it cannot compensate to get the vehicle to idle properly.