Hello again, friends. I notice there are two sensors located on the air intake. I know one of these is the MAP (or, MAF) sensor. I don't know about the other. Can you explain? Also, should both of these be cleaned periodically (I realize the MAP sensor is supposed to be cleaned, don't know about the other one). Thanks.

 

The sensor toward the front of air box
The Inlet Air Temperature/Pressure Sensor is a combination dual-function sensor. The sensor element extends into the intake air stream at the top of the air filter housing. Ambient air temperature as well as barometric pressure is monitored by this sensor. The Engine Control Module (ECM) monitors signals from this sensor.

The sensor to the rear of air box.
The Mass Airflow (MAF) sensor is a frequency based device. A constant voltage is applied to a heated wire on the sensor. This wire is positioned in the air cleaner air stream and is heated by the electrical current that the voltage produces. As air flows across it, it cools down. The heated wire or film is a positive temperature coefficient resistor. This means that its resistance drops when its temperature drops. The drop in resistance allows more current to flow through it in order to maintain the programmed temperature. This current is changed to a frequency which is sent to the Engine Control Module (ECM) and interpreted as air flow. Adjustments for air temperature and humidity are taken into consideration because they also affect the temperature of the heated wire or film.

 

Thanks, Big Iron. I appreciate your not only ID'ing these sensors but also the detailed explanation of each. Further question: Should both be cleaned periodically with the same type of cleaner? I'll pick up your answer tomorrow (signing off)...Thanks

 

Don't clean the MAF sensor. You can mess it up very easily and they aren'
t cheap.

 

I've heard that K&N filter oil works especially well on the MAF...

 

great my mass flow is missing that heated wire, must of got sucked into the turbo

 

Well after installing a K&N air filter and having my mileage drop off about 3 miles to the gallon I thought something was amiss. So after reading how the oil affects the mass flow sensor, I swapped out the KN for an AFE dry filter. I noticed the wire element is not there on the mass flow sensor. I can only assume where it is but, I have ordered a new one hoping this acoounts for the mileage drop.

 

There is another MAF sensor after the turbo that sees EGR flow and gets very sooty. Clean that one, but not the fresh air one. If the sensor wire is missing, you should get a CEL and code.

 

Well I ordered a sensor after reading there should be a wire there. And the new one shows up with no wire, go figure

 

Do you have a CEL and any codes? You should have ordered a code reader instead maybe? If not, you can do the key trick and get your odometer area to display any codes if present...

 

I heard that they can be cleaned instead of costly replace, Maybe electric parts cleaner. Worth a try. JMHO.

 

I was more concerned about the heated wire missing, apparently its not on the 2008 sensor