Case IH 32 – Transmission Control Module / ECM: Forward (Hi-Lo) Synchronizer Solenoid Coil Short Circuit

Triggered when the Forward (Hi-Lo) Synchronizer Solenoid experiences a short circuit while the tractor is driven in forward or in neutral, causing the Transmission Status Lamp (Hi/Rabbit and Lo/Turtle lamps) to flash in an alternating manner.

• JXC
• TN55
• TN65
• TN70
• TN75
• JX 70 U
• JX 80 U
• JX 90 U
• JX 100 U
• Farmall 105C
• Farmall 115C
• Farmall 110U

1. 1

   Test the resistance of the Forward (Hi-Lo) Synchronizer Solenoid coil (expected resistance is approximately 500 Ω to 550 Ω)

2. 2

   If resistance is correct, disconnect the control panel and the connections (137) on the ECM to check for wiring shorts

3. 3

   Check if the wire (HM) on the sensor connection (107) is shorted to ground

4. 4

   Check the wiring continuity between the sensor connection (107), pin (A2) (HM) on connection (177), and pin CN2-25 (HM)

5. 5

   Check for shorts between wires (GL) and (AB) on the wiring side, specifically between connection (71) on the pushbutton and pins (C6) and (A7) on connection (69)

1. 1

   Locate the solenoid

   Locate the Forward (Hi-Lo) Synchronizer Solenoid on the transmission valve block.

2. 2

   Test solenoid resistance

   Disconnect the electrical harness from the solenoid and perform the resistance test (target ~500-550 Ω).

3. 3

   Replace the solenoid

   If the solenoid coil fails the resistance test (indicating an internal short), remove the retaining hardware and replace the Forward (Hi-Lo) Synchronizer Solenoid with a new OEM unit.

4. 4

   Trace wiring harness

   If the solenoid tests within specification, the issue is in the wiring harness. Trace the specific wires (HM, GL, AB) back to the ECM and control panel as outlined in the diagnostic checks to locate the short to ground.

5. 5

   Repair or replace wiring

   Repair the damaged section of the wiring harness, or replace the Hi-Lo Solenoid Valve Wire Harness entirely.

6. 6

   Reconnect components

   Reconnect all ECM and control panel connections.

7. 7

   Clear codes and test

   Clear the fault codes using the Electronic Service Tool (EST) and test drive the tractor in forward and neutral to ensure the Hi/Rabbit and Lo/Turtle lamps no longer flash.