Case IH 12804 – MTA CCM: Failure of TCV pressure sensor supply 'Short to Ground'

The electrical supply voltage circuit going to the TCV (Trailer Control Valve or Transmission Control Valve) pressure sensor has shorted to ground. Because the supply voltage is being pulled to ground, the sensor cannot return a valid pressure signal to the controller.

• MAXXUM T4E
• Stage V MR (Mid-Range) tractors
• CCM LWB with FPS
• APH SWB with FPS and SPS
• APH 16x16 transmission models

1. 1

   Trace the wiring harness from the CCM to the TCV pressure sensor, looking for rubbed insulation or bare metal causing a short to ground.

2. 2

   Disconnect the TCV pressure sensor and inspect the connector for water ingress, corrosion, or bent pins bridging the supply voltage to ground.

3. 3

   With the sensor disconnected and key ON, test the harness supply pin for 0V and continuity to ground to determine if the short is in the harness or internal to the sensor.

1. 1

   Disconnect battery

   Disconnect the tractor's battery to prevent further electrical damage.

2. 2

   Repair or replace harness

   If the diagnostic checks reveal a damaged wire in the harness, splice and repair the wire using weather-sealed heat shrink connectors, or replace the affected harness section.

3. 3

   Remove faulty sensor

   If the harness is intact but the sensor is internally shorted, remove the faulty TCV pressure sensor from the valve block.

4. 4

   Install new sensor

   Install the new TCV pressure sensor and torque to OEM specifications.

5. 5

   Reconnect components

   Reconnect the sensor harness and reconnect the battery.

6. 6

   Clear fault code

   Connect a diagnostic tool to the CCM and clear the inactive 12804 fault code.

7. 7

   Verify repair

   Start the tractor and verify that the code does not return and that transmission/trailer brake pressures read normally.