When it comes to optimizing the performance of your diesel engine, knowing the location and function of critical sensors is paramount. The 3406E engine, a popular choice in the trucking and heavy equipment industry, relies on various sensors to operate efficiently. One such sensor is the atmospheric pressure sensor. In this comprehensive guide, we will delve into the 3406E atmospheric pressure sensor location, its significance, and how it plays a crucial role in maintaining peak engine performance. The sensor that you’re trying to find is look like this
Here the complete procedure on how to remove and install Atmospheric Pressure Sensor
Understanding the Atmospheric Pressure Sensor
Before we explore its location, let’s grasp the importance of the atmospheric pressure sensor. This sensor is responsible for measuring the barometric pressure of the surrounding air. This data is vital for the engine control module (ECM) to calculate air density accurately. Accurate air density information is essential for optimal fuel-air mixture, which directly affects engine performance, fuel economy, and emissions.
The Role of Atmospheric Pressure in Engine Performance
Atmospheric pressure varies with altitude. Engines operating at different altitudes experience variations in air pressure. Understanding these variations is essential because they impact the engine’s performance. At higher altitudes, where atmospheric pressure is lower, there is less oxygen available for combustion. This can lead to reduced engine power and efficiency.
If the signal voltage from the atmospheric pressure sensor is above 4.8 VDC for at least eight seconds. The Electronic Control Module (ECM) will log the diagnostic code. The ECM flags atmospheric pressure as invalid data and a default value of 100 kPa (15 psi) is used. The system will generate CID 0274 FMI 03 error code.
Conversely, at lower altitudes where atmospheric pressure is higher, there is more oxygen available. In such conditions, the engine can produce more power and operate more efficiently. To ensure the engine operates optimally regardless of altitude, the atmospheric pressure sensor constantly monitors barometric pressure and provides this information to the ECM.
Location of the 3406E Atmospheric Pressure Sensor
As you can see on the typical caterpillar cut-off engine diagram bellow, the 3406E Atmospheric Pressure Sensor is located on top side ( 7 ). The atmospheric pressure sensor is located on the drivers side of the engine in front of the engine ECM. It’s in the side of the block. It has three wires. 
3406E Atmospheric Pressure Sensor Location(1) Engine oil pressure sensor
(2) Primary engine speed/timing sensor
(3) Engine coolant temperature sensor
(4) Fuel temperature sensor
(5) Inlet air temperature sensor
(6) Turbocharger compressor outlet pressure sensor
(7) Atmospheric pressure sensor
(8) Secondary engine speed/timing sensor
(9) Fuel pressure sensor
(10) Valve cover connector for injectors
(11) J2/P2 ECM connector
(12) J1 ECM connector
(13) Timing calibration connector
(14) Engine Control Module (ECM)
On a Catepillar C15 I6 Engine the Atmospheric Pressure Sensor is located on the Driver Side, you can see the picture bellow.
I found this video on youtube that explains the location of Atmospheric Pressure Sensor on typical Cat engines.