Massey Ferguson 04.03.91 – Transmission Control Module (TRANS1): Issue With Speed Sensor Values (TRANS1)

This fault code indicates that the transmission controller is receiving erratic, missing, or out-of-range signals from the transmission speed sensor (often the intermediate or input shaft speed sensor). This can result in rough shifting, an inability to find the correct gear, or an erratic/non-functioning speedometer.

• 7724S
• 5712SL
• 7722
• 7722S
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 6400 Series
• 6600 Series
• 6700 Series
• 7614
• 7615
• 7616
• 7617
• 7618

1. 1

   Visual Inspection: Locate the transmission speed sensor (usually accessible from underneath the tractor, threaded into the side of the gearbox cover). Check the weather-resistant housing and the electrical connector for moisture, dirt, or corrosion.

2. 2

   Resistance Test: Disconnect the sensor and measure the resistance across the two pins with a multimeter. Depending on the exact sensor variant, a healthy inductive speed sensor typically reads around 450 Ohms (+/- 20) or 540 Ohms. If it reads open (infinite) or shorted, the sensor has failed.

3. 3

   Signal Test: Check for an alternating AC voltage signal from the sensor pins while the internal pinion/shaft is rotating.

4. 4

   Air Gap Check: Inductive sensors require a precise air gap. If the sensor has backed out slightly, it will fail to read the gear teeth.

1. 1

   Prep the Machine

   Park the tractor on a level surface, engage the parking brake, and disconnect the battery to prevent electrical damage to the transmission controller.

2. 2

   Locate and Clean

   Access the sensor from underneath the tractor. Thoroughly clean the mounting area around the sensor to prevent dirt from falling into the transmission housing when the sensor is removed.

3. 3

   Remove the Old Sensor

   Disconnect the electrical wiring harness and unscrew the faulty speed sensor from the gearbox cover.

4. 4

   Prepare the New Sensor

   Apply a small amount of thread sealant (such as Loctite 5922) to the threads of the new sensor.

5. 5

   Install and Set Air Gap

   Thread the new sensor into the housing. Note for inductive sensors: You generally must screw the sensor in until it bottoms out (touches the internal pinion gear), and then back it off a specified fraction of a turn to set the correct air gap (refer to your specific model's service manual for the exact back-off specification).

6. 6

   Reconnect

   Plug the electrical connector back in and reconnect the tractor's battery.

7. 7

   Clear Codes

   Turn on the tractor and use the in-cab display/monitor to clear the transmission fault codes. Test drive the tractor to ensure smooth shifting and accurate speed readouts.