Or is the Sensor on the Air Intake just a MAF sensor?

 

on the intake is a temp. sensor and the map is on the engine and reads boost..its right by the rail sensor

 

thanks, not speaking of locations per-say though. What I was getting at why two different locations for measuring air intake temp. I can see the relevancy for measuring at the MAP sensor, but does the one on the air filter intake work in-conjunction with the the temp sensor for the grid heater and such?

 

well air temp is only taken at the air filter housing... as for the grid heater not sure off the top of my head right now

 

The MAP (manifold absolute pressure) sensor mounted on the engine intake manifold does NOT measure air temperature, it measures boost pressure.

There is no air temp sensor for the grid heater. The ECM must use a combination of the IAT (intake air temp) sensor on the air intake plus coolant temp plus time to control the grid heater.


Edit, my posted info above is not correct.. Keep reading!!

 

the 2 sensors have absolutely nothing in common... as stated above, the MAP sensor (manifold absolute pressure) reads the pressure, or psi, in the manifold of the engine. this is what your "boost" reading would be if you have a guage.

the sensor on your intake is simply a thermometer... thats it...

 

Without sounding rude, I have no clue where you guys are getting your info but the MAP sensor most certainly DOES measure temperature. The MAP temp is used for timing, grid heater operation, fast idle, etc. It is the intake manifold temp, the one in the air tube pre-turbo is the inlet air temperature, and I really have no clue what it is used for, other than the ECM inputs list doesn't have ambient air temp, so this sensor must be where the ECM gets ambient temp, and explains why the instant 1,000 rpm fast idle can occur on temps above 15*F on the overhead, where the temp in the airbox must still be 15*F or lower, same with the 2 min delays fast idle.

Both sensors read pressure, in absolute. The ECM determines boost by subtracting the ambient (pre-turbo sensor) from the manifold (MAP) sensor, this is how it knows the accurate boost based on altitude.

Anyone who has a scanner that plugs into the OBDII can verify the data. You can watch the IAT's rise and fall with grid heater operation. I am always watching my IAT's, and use it as a basis for how good, or bad, an intake mod was.. Or to know if my ECM will command fast idle after 2 minutes, since IAT's have to be above 66*F for it.

EDIT: Well I just spent 10 minutes typing the verbage from the service manual and the battery died as soon as I hit save.. I forgot to plug the comp in after playing Wii... So now I don't want to re-type it.. so I'll paraphrase.. The Sevice manual lables them both as Sensor Temperature/Pressure. One is Sensor Temperature/Pressure - Intake, the other is Sensor Temperature/Pressure - MAP. The description says that they both relay temperature and pressure info to the ECM.

 

wner:..........

 

Thank you very much Ah64id. After researching the factory service manual last night, I can concur with you statements. However, I should point out that for the Overhead Console Ambient Air Temp. purposes, gets it info from the Ambient Air Temp sensor located drivers side of engine, next to radiator, behind grill. Not really to argue with you, more or less to add to your statements.

Again, thanks Ah64id. It's nice to know there are still people on here informing the mis-lead and adding knowledge to ones who seek it.

 

That was the intent of my statement.

Correct.. thats a driver display only. The ECM gets ambient air temp from the Sensor - Inlet.

 

The overhead temp display, with sensor located behind the grill has nothing to do with how your truck runs, it's fyi only.

Your not talking about the same sensors.


Ah64id, got it right.

 

The overhead temp display, with sensor located behind the grill has nothing to do with how your truck runs, it's fyi only.

That was the intent of my statement.

 

see i learn something new everyday...i love it

map reads air temp Thanks

 

Well I'm sorry for the misinformation. It wasn't intentional & I'll try not to do that again.
I'm far from perfect, just ask my wife! :S:

In all fairness, there was a thread on here or DTR where the wrong info was taken as correct. If I recall, the 2 sensors looked similar but performed different functions.

I also thought that the discussion mentioned that the IAT sensor only had 2 or 3 wire conductors to it while the MAP sensor had 4 or more.
I just popped the hood & both sensors have 4 wire conductors to them.


Thanks to AH64ID for setting us straight with his accurate technical info as always...:thumbsup:

 

No worries, happens to the best of us...