Case IH 148 – TRANS (Transmission Controller): Backup alarm circuit shorted or open

The transmission controller monitors the backup alarm circuit. If the controller detects an open circuit or excessive current draw in the backup alarm circuit, this fault code is recorded. The two most common failure modes are: 1. The backup alarm itself has failed. 2. The backup alarm wiring has failed open or shorted to ground.

• MX Magnum
• STX Steiger
• Magnum 225
• Magnum 250
• Magnum 310
• Magnum 335
• MX210
• MX230
• MX255
• MX285
• TG Series
• T8000 Tractors
• STX 325

1. 1

   Access the transmission controller located underneath the fuse/relay panel.

2. 2

   Visually inspect the wiring harness running from the transmission controller towards the backup alarm at the rear of the machine. Look for abnormal routing, chafing, or wire damage.

3. 3

   Disconnect connector C226 from the transmission controller.

4. 4

   Using a multimeter, measure the resistance between cavity 9 of connector C226 and a good chassis ground on the wiring harness side.

5. 5

   Verify the resistance is around 2 to 5 ohms. If the resistance is dramatically higher, there is an open in the circuit (either a broken wire or a failed alarm internally).

1. 1

   Park the machine on a level surface, turn off the engine, and engage the parking brake.

2. 2

   Perform the diagnostic resistance test at connector C226 (cavity 9) as outlined above.

3. 3

   If the resistance is out of spec (open circuit), trace the harness back to the backup alarm to check for a broken wire.

4. 4

   If the wiring harness is intact and shows continuity from the controller to the alarm connector, the backup alarm unit has failed internally.

5. 5

   Disconnect the harness at the backup alarm.

6. 6

   Remove the mounting screws securing the backup alarm to its support bracket.

7. 7

   Install the new backup alarm and secure it with the mounting hardware.

8. 8

   Reconnect the backup alarm harness and the C226 connector at the transmission controller.

9. 9

   Turn the key to the ON position and place the machine in reverse to verify the alarm sounds and the fault code clears.