CLAAS 75F6h – TR1: Short Circuit on Range B Sensor

The fault code 75F6h indicates a short circuit in the electrical circuit of the transmission range B sensor, which is responsible for informing the transmission control module of the currently selected gear range. This fault is logged by the TR1 (A57-1) transmission control module and is frequently accompanied by a warning that the 'Auto5' fuse is burnt out, pointing to a potential overcurrent situation related to the sensor or its wiring harness.

• Axion 810
• Axion 820
• Axion 830
• Axion 840
• Axion 850
• Arion 500
• Arion 600
• Arion 800

1. 1

   Visually inspect the wiring harness leading to the transmission's range sensor assembly and the range B solenoid valve (Y307) for chafing, melting, pinched wires, or corrosion.

2. 2

   Disconnect and inspect the electrical connectors at the range B contactor (Z154) and the transmission control module (TR1) for bent pins, corrosion, moisture ingress, or loose connections.

3. 3

   Using a multimeter, test the Z154 sensor circuit signal wire for continuity to ground (a continuity reading confirms a short to ground).

4. 4

   Test for a short circuit between the signal wire and the power supply wire in the harness.

5. 5

   Check for an abnormally low signal voltage, which typically indicates a short to a lower electrical potential like battery ground.

1. 1

   Prepare machine for service

   Park the tractor on a level surface, engage the parking brake, turn off the engine, and disconnect the negative battery terminal to prevent electrical shorts during repair.

2. 2

   Locate components

   Locate the range B contactor (Z154) on the exterior of the transmission housing near the mechanical linkages for the range selector forks. Locate the TR1 module, typically found within the cab.

3. 3

   Repair wiring harness

   If diagnostic tests reveal damaged wiring, repair the affected section using appropriate connectors and heat shrink for a sealed repair. Replace any damaged connectors.

4. 4

   Replace range B contactor (Z154)

   If wiring is intact, the Z154 sensor is likely faulty. Disconnect it, remove mounting bolts, and note the alignment of the old sensor. Clean the mounting surface, install the new sensor ensuring correct alignment with the neutral position of the selector shaft, hand-tighten bolts, torque to manufacturer specification, and reconnect.

5. 5

   Perform final operational checks

   Reconnect the battery, start the tractor, and shift through all ranges to verify proper operation. Ensure the dashboard gear indicator displays the correct range and the fault code does not reappear.