Case IH 2158 (519173.03) - DEC – Transmission Control Unit (TCU): Synchro 2-4 Position Sensor - short to high voltage

The control module is receiving a voltage signal from the synchronizer 2-4 position sensor that exceeds the maximum expected threshold (typically shorted to a 5V reference or 12V battery power).

• MAXXUM T4E
• Steiger series
• 9350 Steiger
• Maxxum
• Puma
• CX 50
• CX 60
• CX 70

1. 1

   Check the tractor's battery voltage, as low voltage can cause erratic sensor readings and ghost codes.

2. 2

   Inspect the Synchro position sensor wiring loom for chafing or exposed wires touching a power source.

3. 3

   Disconnect the sensor and check the connector for water ingress, dirt, or bent pins.

4. 4

   Use a multimeter to test the signal wire for a short to the 5V reference or 12V supply wire.

1. 1

   Preparation

   Park the tractor on a level surface, engage the parking brake, and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the Synchro 2-4 Position Sensor on the transmission housing. On some models (like the Steiger), cab removal or lifting may be required to access the top of the transmission.

3. 3

   Measure Sensor Depth

   Before unscrewing the old sensor, take an initial depth measurement. It is very easy to damage the end of the new sensor if it is threaded in too deeply during installation.

4. 4

   Remove the Sensor & Loom

   Disconnect the electrical cable (loom) from the sensor and carefully unthread the sensor from the transmission housing.

5. 5

   Install the New Sensor

   Thread the new sensor into the housing, matching the exact depth measurement taken in Step 3 to ensure proper clearance with the internal synchronizer components.

6. 6

   Replace the Wiring Loom

   If the short to high voltage was caused by a melted or damaged harness, replace the sensor loom.

7. 7

   Reassembly & Calibration

   Reconnect the battery, clear the fault codes via the AFS Pro display or diagnostic tool, and perform a test drive, shifting through the 2-4 synchronizer ranges to verify the repair.