Case IH 2490 (518576.16) - DEC – Transmission Control Module (TCM): Synchro R1-F2 Position Sensor (Signal 2) Short to Vsupply

The signal voltage from the Synchro R1-F2 Position Sensor (Signal 2) is excessively high, registering as a 'short to Vsupply'. This indicates the signal wire is shorted to power, the sensor has an open ground, or the internal potentiometer has failed, preventing the transmission from verifying synchro engagement.

• VESTRUM CVX
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• Maxxum 110-140 EP
• 4065
• 4075
• 4085
• 4095
• 4115
• JX1100U

1. 1

   Visually inspect the wiring harness leading to the R1-F2 synchro sensor on the transmission housing for rubbed-through wires, melted insulation, or damaged connector pins.

2. 2

   Back-probe the sensor connector to verify it is receiving the correct reference voltage and has a solid ground. Check the signal wire for voltage; if it reads equal to the supply voltage, there is a short.

3. 3

   Swap the suspect R1-F2 position sensor with another accessible synchro position sensor (such as the Forward/Reverse synchro sensor). If the fault code moves to the new location, the sensor is internally shorted. If the fault code stays at R1-F2, the short to Vsupply is located in the tractor's wiring harness or the TCM itself.

1. 1

   Access the Sensor

   Locate the Synchro R1-F2 rotary position sensor on the side/top of the transmission housing.

2. 2

   Removal

   Disconnect the electrical harness. Remove the retaining hardware holding the sensor to the synchro shaft (usually an M6 lock nut, a washer/Belleville spring washer, and an M7 circlip/snap ring).

3. 3

   Replacement

   Slide the old potentiometer off the shaft. Install the new rotary position sensor, ensuring the internal tangs align correctly with the synchro shaft.

4. 4

   Reassembly

   Reinstall the circlip, washer, and lock nut. Reconnect the electrical harness.

5. 5

   Transmission Calibration

   Perform a transmission calibration via the tractor's electronic H-Menu / calibration mode to allow the TCM to learn the new minimum and maximum voltage values for the engaged and disengaged positions.