hey guys!

just curious of the symptoms of a failing map/boost sensor?

 

Probably none.......out of wack voltages will set codes. Used to determine baro pressure for starting, I believe. You've still got not SES light on, right?

 

We don't have a boost/map sensor.

We have a MAF sensor.

At least this is true for 5.5 gens.

 

All our cars have a MAP/absolute pressure sensor......the '00s have one mounted on the intake duct under the "hot" radiator hose, and the '01s have theirs mounted next to the ECM, and I think the Gen. 5.5s are integral with the ECM. It isn't reading MAP (manifold pressure downstream of the TB) as non-MAF cars did, and it isn't used for engine control/fuel delivery. This isn't going to be getflushed's problem.

 

 

getflushed understands that he has an MAF......he's changed it a couple of time. I assumed that he was concerned about the absolute pressure sensor which is visible to him on his '00. I think he's been reading stuff related to the old MAP (non MAF) systems, and I made the mistake of referring to it as MAP sensor because it looks like the MAP sensor on my old Beretta.

 

Ok! Thanks p.samson. Yea I've heard issues with the map sensor but after I read your post I checked around and saw that they do not play as big of a role when a MAF sensor is involved thanks for your help!

 

There is a boost sensor on the vehicle. It isn't negligible. When this thing is unplugged(or has failed) you will get a SES light. You will definitely feel a difference in the performance of the vehicle as well. It won't be "fall-on-your-face-MAF-gone" type loss, but you'll feel it. This applies to 4th, 5th, and 5.5. This was my first and only SES on my 4th gen. I accidently forgot to plug it in after my starter replacement.

 

nelledge is right. Plus your idle will have some issues spirratically

 

An absolute pressure sensor is a MAP sensor.....But Maxima have been running MAF for a fact since 1985.....But are you referring to the sensor in the intake duct tract before the filter?

 

Yes an MAP sensor can be an absolute pressure sensor, but the absolute pressure sensor on our cars is not technically a MAP sensor. "Manifold pressure" is understood to be the air pressure (negative (vacuum) or positive (boost)) between the throttle and the cylinders. The absolute pressure sensor on the '00 is the sensor that is attached to the stock intake scoop. It is sensing only the pressure in the intake duct upstream of the TB (just downstream of the stock air filter housing), where it's sense hose is physically attached). Obviously with the engine not running it's reading ambient pressure. As I mentioned above this sensor was relocated under the dash on the '01 cars (I don't know if it is still sensing intake duct pressure or just ambient all the time). The Gen. 5.5 cars have an integral ECM sensor which I'm sure is just open to atmosphere (sensing ambient pressure). This sensor can set a code if the ECM sees a low or high voltage from it. The Nissan FSMs do not explain the function of this absolute pressure sensor on our Maxis, nor is it mentioned in any troubleshooting charts/matrixes or procedures for any performance or starting engine issues, or for any reason other than in relation to it's two associated fault codes. But I know with other cars the explanation is that it is used to sense the ambient pressure/altitude and the ECM uses this to "tweak" the mixture for starting/warmup.

 

will a failing MAP sensor throw a P0105?

I have that code showing now and have not checked this sensor.

 

1St time writing would the map boost sensor have anything to do w a5th gen starting in the morning? Mine never starts first try and winter time rough idle other than that 128k car is still sound

 

Sounds more like a sticky IAC motor.

 

Mounted behind the climate control, right? But doesn't do anything except for high elevation...?