Case IH 2679 (518576.12) - DEC – DEC (Drivetrain Electronic Controller) / Transmission Control Unit (TCU): Synchro R1/F2 Position Sensor - incoeherence on signals 1-2

Indicates an incoherence between the dual signals of the Synchro F2-R1 Position Sensor. The transmission controller is receiving conflicting, implausible, or out-of-range voltage signals from the sensor's two signal tracks, making it impossible for the system to verify whether the synchronizer is in F2, R1, or neutral.

• VESTRUM CVX
• Case IH Magnum 210
• Case IH Magnum 220
• Case IH Magnum 240
• Case IH Magnum 340

1. 1

   Visually inspect the X-533 Synchro F2-R1 Sensor 3-pin connector for corrosion, moisture, or backed-out pins.

2. 2

   Test the wiring harness at the X-533 connector using a multimeter to verify Pin 1 (Blue wire, circuit 7584 Signal), Pin 2 (Green wire, circuit 7525 5V Supply), and Pin 3 (Black/White wire, circuit 60 Ground).

3. 3

   Check for related fault codes (such as 2517-2522) that might point to a mechanical or solenoid failure rather than the sensor itself.

4. 4

   Mechanically verify that the F2 (X-639) and R1 (X-644) solenoids are functioning and that the synchronizer is not mechanically jammed.

1. 1

   Access the Sensor

   Locate the Synchro F2-R1 position sensor on the upper right-hand side of the transmission housing.

2. 2

   Disconnect and Clean

   Disconnect the 3-way Bosch BDK connector. Clean the area around the sensor to prevent dirt from entering the transmission.

3. 3

   Harness Repair

   If the connector is damaged, splice in a new connector pigtail (Part # 87747172) ensuring weather-tight seals on the splices.

4. 4

   Sensor Replacement

   If the wiring tests good (steady 5V and ground present), the sensor's internal potentiometer tracks have likely failed. Remove the retaining hardware, extract the old sensor, and install the new OEM sensor.

5. 5

   Transmission Calibration

   After replacing the sensor or repairing the harness, you must perform a transmission calibration using the tractor's display or an electronic service tool to teach the DEC the new voltage values for the physical F2 and R1 end-stops.