Case IH 3509-04 - ITBV – ITBV: Sensor Supply Voltage #1 out of range low / Trailer brake control line pressure sensor voltage low

The control module is detecting that the 5V DC reference supply voltage to the trailer brake control line pressure sensor has dropped below the normal operating range (typically less than 4.5 VDC). This condition is usually caused by the sensor circuit being shorted to ground, an internally shorted sensor, or a compromised wiring harness.

• MAGNUM AFS Connect
• Case IH AFS Connect Magnum Series (Models 180, 200, 220, 240, 250, 280, 310, 340, 380)
• Case IH Puma Series (Puma 185-260 CVX, Puma 200)
• Case IH Maxxum Series (CVXDrive)
• Case IH Optum Series (CVXDrive)

1. 1

   Plausibility Check: Verify the brake pedal output status via the diagnostic menu. Look for conflicting data, such as the brake switch reading 'low' while the demand pressure sensor reads 'high'.

2. 2

   Connector Inspection: Disconnect the wiring harness from the ITBV module and the pressure sensor. Inspect the pins and connectors for moisture, corrosion, or conductive wire filaments that could cause an intermittent short.

3. 3

   Voltage Supply Test: Turn the key ON (engine off). Measure the reference voltage coming from the ITBV module to the sensor. It should be a steady 5 VDC. If it is significantly lower, the module or the harness is pulling the voltage down.

4. 4

   Short-to-Ground Test: With the battery disconnected, test the sensor wiring harness for continuity to ground. A shorted wire will pull the 5V supply down, triggering the 3509-04 code.

1. 1

   Power Down

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

2. 2

   Expose the Sensor

   Locate the pneumatic trailer brake pressure sensor along the trailer brake control line (often routed near the ITBV solenoid valve block at the rear of the tractor).

3. 3

   Isolate the Fault

   If the wiring harness passed the short-to-ground test and the module is outputting 5V when the sensor is unplugged, the sensor itself is internally shorted.

4. 4

   Replace the Sensor

   Depressurize the air/hydraulic brake lines before removing the sensor. Unplug the electrical connector. Unthread the faulty pressure sensor from the brake line/valve block. Install the new OEM pressure sensor and torque to factory specifications.

5. 5

   Reassemble and Clear Codes

   Reconnect the electrical harness, reconnect the battery, and power on the tractor. Use the electronic service tool to clear the 3509-04 fault code.

6. 6

   Test Operation

   Actuate the brake pedal and verify that the trailer brake pressure registers correctly without the voltage dropping low.