Case IH 19621 – VCM (Vehicle Control Module) / Engine ECU: Ambient and Boost pressure are different at start

At key-on (before the engine is cranked or running), there is no turbocharger boost being generated. Therefore, the Boost Pressure Sensor (Intake Manifold Pressure) and the Ambient Air Pressure Sensor (Barometric Pressure) should read the exact same atmospheric pressure. If the control module detects a significant variance between the readings of these two sensors at startup, it logs fault code 19621. This indicates that one of the sensors is out of calibration, has failed, or has a wiring issue.

• Tier 4b
• 580N
• 580SN
• 580SN WT
• 590SN
• SR130
• SR160
• SR175
• SV185

1. 1

   Connect an OEM-compatible diagnostic scan tool and view live data for Ambient Air Pressure and Boost Pressure with the key ON and engine OFF.

2. 2

   Compare both sensor readings to your actual local barometric pressure to identify which sensor is faulty (the one deviating significantly is the culprit).

3. 3

   Inspect the wiring harness and connector for the suspect sensor for chafed wires, moisture intrusion, or corroded pins.

4. 4

   If the boost pressure sensor is the culprit, remove it and inspect the sensor tip and the intake manifold port for soot buildup or debris.

1. 1

   Turn off ignition and disconnect battery

   Turn off the machine's ignition and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate faulty sensor

   Locate the faulty sensor identified during the diagnostic phase (the boost pressure sensor is located on the intake manifold piping; the ambient pressure sensor is typically mounted on the engine harness or ECU bracket).

3. 3

   Disconnect harness

   Depress the locking tab and disconnect the electrical harness connector from the sensor.

4. 4

   Remove sensor

   Remove the retaining bolt(s) or unscrew the sensor from its mounting port.

5. 5

   Clean mounting surface

   Carefully clean the mounting surface. Note: If replacing the boost pressure sensor, ensure no dirt, soot, or debris falls into the intake manifold.

6. 6

   Install new sensor

   Install the new replacement sensor and tighten it to the OEM torque specification.

7. 7

   Reconnect harness

   Reconnect the electrical harness connector, ensuring it clicks securely into place.

8. 8

   Reconnect battery

   Reconnect the negative battery cable.

9. 9

   Clear fault code

   Turn the key to the ON position and use your diagnostic scan tool to clear the inactive 19621 fault code.

10. 10

    Verify repair

    Verify the repair by checking the live data again to ensure both pressure sensors now read the same atmospheric pressure before starting the engine.