Dodge Nitro. Manual - part 681

Fig. 99: Identifying Intake Manifold Air Temperature (IAT) Sensor & Electrical Connector 
Courtesy of CHRYSLER LLC 

The intake manifold air temperature (IAT) sensor (1) is installed into the rubber air intake tube near the throttle 
body. 

1. Clean mounting hole.  

2. Check condition of sensor O-ring.  

3. Push IAT sensor (1) into rubber intake tube while rotating for installation.  

4. Connect electrical connector (2) to IAT sensor.  

INSTALLATION - 4.0L 

 

2007 Dodge Nitro R/T 

2007 ENGINE Fuel System - Nitro

  

Fig. 100: Identifying Electrical Connector & IAT Sensor
Courtesy of CHRYSLER LLC 

The intake manifold air temperature (IAT) sensor (2) is installed into the rubber air intake tube near the throttle 
body. 

1. Clean mounting hole.  

2. Check condition of sensor O-ring.  

3. Push IAT sensor (2) into rubber intake tube while rotating for installation.  

4. Connect electrical connector (1) to IAT sensor.  

SENSOR-MANIFOLD AIR PRESSURE 

OPERATION 

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR - PCM INPUT 

The MAP sensor is used as an input to the Powertrain Control Module (PCM). It contains a silicon based 
sensing unit to provide data on the manifold vacuum that draws the air/fuel mixture into the combustion 
chamber. The PCM requires this information to determine injector pulse width and spark advance. When 
manifold absolute pressure (MAP) equals Barometric pressure, the pulse width will be at maximum. 

A 5 volt reference is supplied from the PCM and returns a voltage signal to the PCM that reflects manifold 
pressure. The zero pressure reading is 0.5V and full scale is 4.5V. For a pressure swing of 0-15 psi, the voltage 
changes 4.0V. To operate the sensor, it is supplied a regulated 4.8 to 5.1 volts. Ground is provided through the 
low-noise, sensor return circuit at the PCM. 

The MAP sensor input is the number one contributor to fuel injector pulse width. The most important function 
of the MAP sensor is to determine barometric pressure. The PCM needs to know if the vehicle is at sea level or 
at a higher altitude, because the air density changes with altitude. It will also help to correct for varying 
barometric pressure. Barometric pressure and altitude have a direct inverse correlation; as altitude goes up, 
barometric goes down. At key-on, the PCM powers up and looks at MAP voltage, and based upon the voltage it 
sees, it knows the current barometric pressure (relative to altitude). Once the engine starts, the PCM looks at the 
voltage again, continuously every 12 milliseconds, and compares the current voltage to what it was at key-on. 
The difference between current voltage and what it was at key-on, is manifold vacuum. 

During key-on (engine not running) the sensor reads (updates) barometric pressure. A normal range can be 
obtained by monitoring a known good sensor. 

As the altitude increases, the air becomes thinner (less oxygen). If a vehicle is started and driven to a very 
different altitude than where it was at key-on, the barometric pressure needs to be updated. Any time the PCM 
sees Wide Open Throttle (WOT), and RPM, it will update barometric pressure in the MAP memory cell. With 
periodic updates, the PCM can make its calculations more effectively. 

The PCM uses the MAP sensor input to aid in calculating the following: 

Manifold pressure  

 

2007 Dodge Nitro R/T 

2007 ENGINE Fuel System - Nitro

  

Barometric pressure  

Engine load  

Injector pulse-width  

Spark-advance programs  

Shift-point strategies (certain automatic transmissions only)  

Idle speed  

Decel fuel shutoff  

The MAP sensor signal is provided from a single piezoresistive element located in the center of a diaphragm. 
The element and diaphragm are both made of silicone. As manifold pressure changes, the diaphragm moves 
causing the element to deflect, which stresses the silicone. When silicone is exposed to stress, its resistance 
changes. As manifold vacuum increases, the MAP sensor input voltage decreases proportionally. The sensor 
also contains electronics that condition the signal and provide temperature compensation. 

The PCM recognizes a decrease in manifold pressure by monitoring a decrease in voltage from the reading 
stored in the barometric pressure memory cell. The MAP sensor is a linear sensor; meaning as pressure changes, 
voltage changes proportionately. The range of voltage output from the sensor is usually between 4.6 volts at sea 
level to as low as 0.3 volts at 26 in. of Hg. Barometric pressure is the pressure exerted by the atmosphere upon 
an object. At sea level on a standard day, no storm, barometric pressure is approximately 29.92 in Hg. For every 
100 feet of altitude, barometric pressure drops 0.10 in. Hg. If a storm goes through, it can change barometric 
pressure from what should be present for that altitude. You should know what the average pressure and 
corresponding barometric pressure is for your area. 

REMOVAL 

REMOVAL 

Fig. 101: Identifying MAP Sensor - 4.0L 
Courtesy of CHRYSLER LLC 

 

2007 Dodge Nitro R/T 

2007 ENGINE Fuel System - Nitro

  

The Manifold Absolute Pressure (MAP) sensor (2) is mounted into the top/front of the upper half of the intake 
manifold. 

An O-ring is used to seal the sensor to the intake manifold. 

1. Disconnect electrical connector (1) at sensor (2).  

2. Clean area around MAP sensor.  

3. Rotate sensor 1/4 turn counter-clockwise until tangs align.  

4. Pull MAP sensor from intake manifold.  

5. Check condition of sensor O-ring.  

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR 

Fig. 102: Identifying MAP Sensor - 3.7L 
Courtesy of CHRYSLER LLC 

The Manifold Absolute Pressure (MAP) sensor (7) is mounted into the front of the intake manifold (1). 

1. Disconnect electrical connector (2) at sensor.  

2. Clean area around MAP sensor.  

3. Remove one sensor mounting screw (8).  

4. Remove MAP sensor from intake manifold by slipping it from locating pin (6). 

 

2007 Dodge Nitro R/T 

2007 ENGINE Fuel System - Nitro