Case IH 518506-03 - BCM – BCM: Cab delta pressure sensor - out of range - high

The control module is receiving a voltage signal from the cab delta pressure sensor that exceeds the maximum expected threshold. This typically indicates that the sensor's signal wire is shorted to power (5V or 12V), the sensor has lost its ground connection, or the sensor itself has failed internally.

• MAGNUM AFS Connect
• Steiger
• Quadtrac
• Optum

1. 1

   Locate the cab delta pressure sensor (typically mounted near the cab fresh air intake, HVAC blower assembly, or cab roof module). Inspect the sensor's wiring harness and connector for pinched wires, moisture intrusion, or bent pins.

2. 2

   Disconnect the sensor. Turn the key to the ON position. Use a multimeter to verify the reference voltage (usually 5V) from the BCM to the sensor.

3. 3

   Test the sensor's ground circuit for continuity to the chassis or the BCM ground return. An open ground will cause the signal voltage to float high, triggering the 'out of range - high' code.

4. 4

   Test the signal wire for a short to power. If the signal wire shows voltage when disconnected from the sensor, there is a short in the harness.

5. 5

   Ensure the small pneumatic tubes/hoses connected to the delta pressure sensor are not blocked, kinked, or disconnected, though an 'out of range high' code is almost always an electrical circuit failure rather than a pneumatic one.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes.

2. 2

   Access the Sensor

   Remove the necessary cab trim or exterior filter housing panels to access the cab delta pressure sensor.

3. 3

   Repair Wiring

   If your diagnostic checks revealed a short to power or an open ground in the harness, repair the damaged section of the wiring or replace the affected harness pigtail.

4. 4

   Replace the Sensor

   If the wiring tests perfectly, the sensor has failed internally. Unplug the electrical connector, carefully pull off the pressure reference hoses (note their orientation), and unbolt the sensor bracket. Install the new sensor and reattach the hoses and connector.

5. 5

   Clear Codes

   Reconnect the battery. Turn the key ON and use the AFS Pro display, Jaltest, or CNH Electronic Service Tool (EST) to clear the inactive BCM fault codes.

6. 6

   Test Operation

   Start the tractor, turn the HVAC blower to maximum, and verify that the cab pressurization system operates normally without throwing the 518506-03 code.