John Deere 1639.16 – Engine Control Unit (ECU): Fan Speed Higher Than Expected

The Engine Control Unit has detected that the rotational speed signal from the cooling fan is slightly above the expected or commanded value. This code is directly related to the variable speed fan drive system, specifically the proportional solenoid valve for the charge air cooler / engine cooling fan.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8270
• 8330
• 7R Series
• 8R Series
• 8310RT
• 8335RT
• 8360RT
• 6.8L PowerTech Diesel Engine
• 8.1L PowerTech Diesel Engine
• 9.0L PowerTech Diesel Engine

1. 1

   Check the fan drive system and ensure that the bleed screw located under the fan drive is fully closed

2. 2

   Inspect the fan drive belt for wear, glazing, or damage, as even a small lip or irregularity can cause fan speed fluctuations

3. 3

   Inspect the fan speed sensor and its wiring harness for shorts, high voltage, or electrical noise

4. 4

   Check the proportional solenoid valve for the charge air cooler/fan drive to ensure it is not stuck open or mechanically failing

1. 1

   Secure the Machine

   Park the machine on a level surface, turn off the engine, and remove the key. Allow the engine and cooling system to cool down completely.

2. 2

   Close the Bleed Screw

   Locate the bleed screw on the variable speed fan drive. If it is loose or open, tighten it until it is fully closed. Clear the code and test the machine to see if the fault returns.

3. 3

   Replace the Fan Belt

   If the bleed screw was closed but the code persists, remove the fan belt tensioner and inspect the belt. If there is any lip, fraying, or stretching, replace the fan belt with a new OEM belt.

4. 4

   Test/Replace the Fan Speed Sensor

   If the mechanical drive is intact, use a multimeter to test the fan speed sensor circuit. If the sensor is outputting erratic signals or has failed, remove the mounting bolt, extract the old sensor, and install a new fan speed sensor.

5. 5

   Service the Proportional Solenoid Valve

   If the sensor is functioning properly, the proportional valve cartridge or coil controlling the fan fluid flow is likely faulty. Relieve hydraulic pressure, remove the proportional solenoid valve coil and cartridge from the fan drive manifold, and replace them.

6. 6

   Clear Codes

   Reconnect all harnesses, start the engine, and use a diagnostic tool to clear the ECU 001639.16 code. Run the engine up to operating temperature to verify the fan speed regulates correctly.