Case IH 177-04 - DEC – Transmission Control Unit (TCU) / Instrument Cluster Unit (ICU) / Armrest Control Module (ACM): Transmission Oil Temperature - Voltage Below Normal / Short Circuit to Ground

The control module is receiving a voltage signal from the transmission oil temperature sensor that is lower than the acceptable minimum threshold. This typically means the sensor wire is shorted to ground, the sensor has failed internally (creating a dead short), or there is a fault within the controller itself.

• MAGNUM AFS Connect
• Maxxum Series (110, 115, 125, 130, 140, 150)
• Puma Series (130 through 240)
• Magnum Series
• Optum Series
• Older MX Series (MX80C, MX100, MX110, MX120, MX135)
• Steiger / TJ Series (TJ275 through TJ530)

1. 1

   Inspect the wiring harness between the transmission oil temperature sensor and the ECU for visible damage, rubbing, or pinched wires that could cause a short to ground.

2. 2

   Disconnect the sensor and inspect the electrical connector for moisture, corrosion, or bent pins.

3. 3

   Perform a 'Wiggle Test' on the machine's wiring harness using a diagnostic service tool while monitoring the sensor voltage to identify intermittent shorts.

4. 4

   Test the signal wire for continuity to ground using a multimeter.

5. 5

   Test the sensor's resistance with a multimeter; if it reads near zero ohms, the sensor is internally shorted and must be replaced.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes during repair.

2. 2

   Locate the Sensor

   Locate the transmission oil temperature sensor, which is threaded into the transmission sump/housing.

3. 3

   Disconnect

   Unplug the electrical connector from the sensor.

4. 4

   Prepare for Fluid Loss

   Place a clean drain pan underneath the sensor area, as removing the sensor may result in a small amount of transmission fluid loss.

5. 5

   Remove and Replace

   Unscrew the faulty sensor. Quickly thread in the new OEM replacement sensor to minimize fluid loss, and tighten to the manufacturer's torque specification.

6. 6

   Reconnect

   Plug the electrical harness back into the new sensor.

7. 7

   Clear Codes

   Reconnect the battery, turn the ignition on, and use the AFS Pro display or a diagnostic tool to clear the active 177-04 fault code.

8. 8

   Verify

   Start the tractor and verify that the transmission temperature reads correctly on the dash and that the code does not return. Top off transmission fluid if a significant amount was lost.