Case IH 51 – Transmission Electronic Control Module (Transmission ECM / Controller): Transmission Temperature Sender Open Circuit

The control module detects that the voltage from the transmission temperature sender is too high (typically above 4.5 volts at the ECM connector pin). This indicates that the circuit is open, the sensor is unplugged, or there is a short to a 5V or 12V power source. When this fault is active, the transmission assumes an extreme low-temperature state, resulting in sluggish shifting, low clutch pack pressures, and a clutch pedal that engages higher than normal during inching.

• JXC
• TN / TNA Series
• MXM Series
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• Maxxum Series
• Puma Series
• Magnum Series
• TG Series

1. 1

   Verify actual transmission oil temperature (extreme cold below -30°C / -22°F can cause a false trigger that resolves when warmed up).

2. 2

   Inspect the wiring harness and connector at the transmission temperature sender for damage, corrosion, or a disconnected plug.

3. 3

   Test the wiring between the Transmission ECM and the sender for an open circuit, a short to 12 volts, or a short to the 5-volt reference.

4. 4

   Measure the resistance of the transmission temperature sender to determine if the internal thermistor has failed open.

1. 1

   Cool down transmission

   Park the tractor on a level surface, apply the parking brake, turn off the engine, and let the transmission cool to a safe temperature.

2. 2

   Locate sender

   Locate the transmission temperature sender on the main speed transmission gearbox case or hydraulic system module.

3. 3

   Disconnect and clean

   Disconnect the electrical harness connector from the sender and clean the area around the mounting threads to prevent dirt from entering the transmission.

4. 4

   Remove faulty sender

   Unscrew and remove the faulty temperature sender. Be prepared to catch a small amount of transmission fluid.

5. 5

   Install new sender

   Apply appropriate thread sealant to the new sensor (if not pre-applied) and thread it into the transmission case. Tighten to OEM specifications.

6. 6

   Reconnect harness

   Reconnect the electrical harness securely.

7. 7

   Warm up transmission

   Start the tractor and allow the transmission oil to warm up (a minimum of 50°C / 122°F is often recommended for testing and calibration).

8. 8

   Clear fault codes

   Clear the fault codes using the tractor's diagnostic display (e.g., H-Menu) or a service tool.

9. 9

   Perform calibration

   If the shift quality remains sluggish or clutch featherability has noticeably deteriorated after the repair, a transmission/clutch calibration procedure must be performed.