Case IH 2812 – Transmission Controller (Trans / TCU): Transmission Oil Temperature sensor short to B+ or open circuit.

The controller is receiving a voltage signal from the transmission oil temperature sensor that is out of the normal operating range—specifically, the circuit is either completely broken/disconnected (open circuit) or the sensor's signal wire is shorted directly to battery voltage (B+).

• Magnum
• Steiger T4B
• Case IH Magnum 235 – 340 (Series 4)
• Case IH Steiger
• Case IH Puma

1. 1

   Visually inspect the wiring harness leading to the transmission oil temperature sensor for pinched wires, rubbed-through insulation, or broken wires.

2. 2

   Disconnect the sensor and inspect the connector pins for corrosion, moisture, or bent pins that could cause an open circuit.

3. 3

   Use a multimeter to test the resistance across the sensor's terminals. If it reads as completely open (infinite resistance), the sensor has failed internally.

4. 4

   With the key on and the sensor unplugged, check the signal wire for voltage. If it reads full battery voltage (B+), there is a short to power in the wiring harness.

1. 1

   Power Down

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

2. 2

   Locate the Sensor

   Locate the transmission oil temperature sensor on the transmission housing.

3. 3

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a broken wire or a short to B+ in the harness, repair the damaged section of the wiring harness or replace the connector pigtail.

4. 4

   Replace the Sensor (If Applicable)

   If the wiring is intact and the sensor tested as an open circuit: Clean the area around the sensor to prevent dirt from entering the transmission. Unscrew and remove the faulty transmission oil temperature sensor. Have a catch pan ready, as a small amount of transmission fluid may leak. Install the new OEM sensor and tighten it to the manufacturer's specified torque.

5. 5

   Reassembly

   Plug the electrical connector back into the sensor, ensuring it clicks and locks into place.

6. 6

   Clear Codes

   Reconnect the battery, turn the key on, and use the tractor's onboard diagnostic menu or an Electronic Service Tool (EST) to clear the fault code.

7. 7

   Test

   Start the tractor and monitor the transmission temperature readout to ensure it is functioning correctly and the code does not return.