I picked up a 2001 qx4 from a guy. It had been to 3 shops and they couldn't figure out the misfire problem (so im told). I hauled it to my shop and found that the driver for the #3 cylinder in the ECU was not firing so time for a new ECU.

pulled one out of a 2001 nissan pathfinder at the wrecking yard

Programed the key and it fired right up but surges up and down and barely runs when it drops below 600rpm

when I pulled the old computer out there was a boost/map sensor attached to the ecm mount, but no vacuum line attached to it. (there is a connector attached.) I searched up in the dash but cannot for the life of me find a vacuum line to attach it to.

Also, it appears that the new ECM did not have this sensor attached to the frame that I could tell. (it was in a front end collision and the dash was pushed back so far it was hard to get to the ECM to pull it out. It may have just broken off up in the dash.

Micthell on demand says this is the absolute pressure sensor.

does anybody know where the vacuum line for this sensor is suppose to run? the vacuum diagrams on mitchell doesn't even show it.

Side Notes.
the computer does not have the same number as the one that was originally in the car

I was able to program my old key to the ECU but my air relearn would not complete. (first time ive used this particular scanner for that function).

i can post pics if needed

The pressure sensors that mount on top of the ECM are only used for BARO and not MAP, thus no MAP/BARO solenoid and no vacuum line.

Thank you.

Another quick question. Does anybody know if the ecm numbers have to match? I'm pretty sure this is the wrong ECM as the pins on the connector don't quite match what's on the car now. Haven't looked at what those pins are yet.

Are the Nissan computers different then the infinity? Seems every Infinity in the yard has the computer pulled but the Nissans are still there. And all the Nissan computers seem to be of the same number.

If the Hitachi/JEC part number is the same then the hardware will swap, but you'll probably need to have the firmware reprogrammed to work with your ride.