Case IH 1079-04 - ITBV – ITBV: Sensor Supply Voltage 1 Below Normal Operating Range or Shorted to Low Source

The 5V sensor supply voltage (Sensor Supply Voltage 1) to the tractor service brake pressure sensor is below the normal operating range (typically less than 4.0V or 4.5V) or shorted to a low source (ground). This means the control module is detecting an abnormally low voltage on the reference circuit, which is usually caused by a short to ground in the wiring harness or an internally shorted pressure sensor pulling the reference voltage down.

• MAGNUM AFS Connect
• Case IH AFS Connect Magnum Tractors (Models 180, 200, 220, 240, 250, 280, 310, 340, 380)
• Case IH Maxxum Series
• Case IH Puma Series
• Case IH Optum Series
• Case IH Farmall Series (e.g., 105U)

1. 1

   Inspect the wiring harness between the ITBV module and the service brake pressure sensor for chafing, rubbing, or pinched wires that could cause a short to ground.

2. 2

   Perform a sensor isolation test: Disconnect the service brake pressure sensor and measure the supply voltage at the harness connector with the key ON. If the voltage returns to a steady 5V, the sensor is internally shorted.

3. 3

   Perform a harness continuity test: If the voltage remains low with the sensor disconnected, disconnect the harness at the ITBV module and check the 5V supply wire for continuity to ground.

4. 4

   Inspect the sensor and ITBV module connectors for water ingress, corrosion, or bent pins that could bridge the 5V supply to a ground pin.

1. 1

   Prepare tractor for service

   Park the tractor on a level surface, apply the parking brake, turn off the engine, and disconnect the battery to prevent electrical spikes.

2. 2

   Relieve pressure

   Relieve any residual hydraulic or pneumatic pressure in the tractor and trailer brake system.

3. 3

   Locate sensor

   Locate the service brake pressure sensor, which is typically threaded into the ITBV manifold/valve block or the trailer brake tube assembly.

4. 4

   Repair wiring harness

   If the diagnostic checks pointed to a wiring short, repair or replace the affected section of the wiring harness.

5. 5

   Remove faulty sensor

   If the sensor was deemed faulty, disconnect its electrical connector and carefully unscrew the faulty brake pressure sensor.

6. 6

   Install new sensor

   Install the new brake pressure sensor (ensure any required O-rings or thread sealants are in place) and tighten it to the manufacturer's specification.

7. 7

   Reconnect connector

   Reconnect the electrical connector.

8. 8

   Clear fault code

   Reconnect the battery, turn the ignition key to the ON position, and use a diagnostic service tool to clear the 1079-04 fault code.

9. 9

   Test brake system

   Start the tractor and test the brake system (both tractor and trailer circuits) for proper operation and ensure the fault code does not return.