Massey Ferguson 171.1 – Engine ECU: Ambient Temperature Sensor Voltage Issue

The engine control module is receiving erratic, rapidly fluctuating, or implausible voltage signals from the ambient air temperature sensor that do not align with normal environmental temperature changes.

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4700 Series
• 5600 Series
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5700 Series
• 7600 Series
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 7700 Series
• 7714 to 7726S
• 8600 Series

1. 1

   Visually inspect the ambient temperature sensor (typically mounted near the front grille, air intake, or behind the cab steps), its 2-pin oval connector, and the wiring harness for chafing, moisture ingress, or corrosion.

2. 2

   Disconnect the sensor and check the harness side for a steady 5V reference signal and a good ground from the ECU. Wiggle the harness while testing to check for intermittent breaks.

3. 3

   Perform a sensor resistance test across the two pins. A standard replacement is rated at roughly 5000 Ohms at 25°C (77°F). If the resistance is open, shorted, or jumps erratically when tapped, the sensor is faulty.

1. 1

   Power Down

   Turn off the tractor and disconnect the negative battery terminal to prevent accidental shorts to the ECU.

2. 2

   Locate and Disconnect

   Locate the ambient temperature sensor. Depress the locking tab on the 2-pin oval connector and pull it free.

3. 3

   Remove the Sensor

   Carefully pull or pry the old sensor out of its mounting bracket (pressed/friction fit).

4. 4

   Install the New Sensor

   Press the new sensor firmly into the mounting hole until it is fully seated.

5. 5

   Reconnect

   Apply a small amount of dielectric grease to the connector to prevent future moisture issues, and plug the 2-pin connector back in until it clicks.

6. 6

   Clear Codes

   Reconnect the battery. Turn the ignition on and use a diagnostic scan tool to clear the 000171.10 fault code from the Engine ECU.