John Deere 186.05 – RPT: Rear PTO Speed Sensor, Open Circuit

This diagnostic trouble code is generated when the control software detects that the voltage at the output to the rear PTO speed sensor is too high, which indicates an open circuit. An open circuit means there is a physical break or disconnection in the electrical pathway, preventing the sensor from sending accurate RPM data to the tractor's computer. When this error is detected, the functionality of the rear PTO is significantly limited or becomes entirely non-functional, which will prevent the operation of the connected implement. You may also see erratic or missing RPM readings on the cab monitor.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5M
• 5R
• 5E
• 5075M
• 5115M
• 6M
• 6R
• 6MC
• 6RC
• 6090MC
• 6230
• 6430
• 7R
• 8R
• 8225R
• 8400R

1. 1

   Visually check the wiring harness leading to the rear PTO speed sensor for any signs of an open circuit, such as chafed, broken, or melted wires

2. 2

   Ensure the plug connecting to the rear PTO speed sensor is secure. Disconnect it and check for dirt, moisture, or corroded pins. Clean the connector and reconnect it tightly

3. 3

   Use a digital multimeter to test the rear PTO speed sensor and its associated circuit for continuity. If the wiring harness tests fine but the sensor shows no continuity, the sensor itself has failed internally

4. 4

   Ensure the sensor is sitting at the correct gap from the tone ring/clutch fins inside the housing, as physical damage or improper spacing can cause reading failures

1. 1

   Safety First

   Turn off the tractor and disconnect the battery to prevent any electrical damage or shorts during the repair.

2. 2

   Locate the Sensor

   Locate the Rear PTO Speed Sensor, which is mounted on the rear PTO housing/gearbox area. Access can sometimes be tight depending on the tractor model.

3. 3

   Remove the Faulty Sensor

   Unplug the wiring harness connector from the sensor. Unbolt and carefully pull the old sensor out of the housing.

4. 4

   Install the New Sensor

   Insert the new PTO speed sensor into the housing. Ensure it is seated properly so that the gap between the sensor and the internal tone ring is correct (refer to your specific model's manual, but it is often set to a tight tolerance like 2 ± 1 mm).

5. 5

   Reconnect

   Plug the weather-sealed wiring harness connector back into the new sensor.

6. 6

   Test Operation

   Reconnect the battery. Start the tractor, engage the PTO, and check your display monitor. You should now see steady RPM readings that match your tachometer. Clear the 000186.05 fault code from the RPT module.