John Deere 000186.01 – BCU: Front PTO Speed Too Slow During Start Up

The Front PTO is not reaching its expected rotational speed during the startup sequence. The Basic Control Unit (BCU) commands the front PTO to engage, but the speed sensor reports a velocity below the minimum required threshold. This triggers the control unit to shut down the PTO as a protective measure to prevent damage to the clutch and implement.

• 6R Series
• 7R Series
• 8R Series
• 6M Series

1. 1

   Verify the correct operator procedure for engaging the front PTO is being followed, ensuring adequate engine RPM during engagement

2. 2

   Check the front PTO driveshaft and any attached implement for mechanical obstructions or heavy binding loads

3. 3

   Inspect transmission/hydraulic fluid level and condition (must be Hy-Gard or J20C equivalent oil)

4. 4

   Listen for a distinct 'click' from the front PTO control solenoid when activated to verify it is receiving an electrical signal

5. 5

   Visually inspect the wiring harnesses and connectors for the front PTO speed sensor and solenoid for damage, corrosion, loose connections, or chafing

1. 1

   Retrieve DTCs

   Use the tractor's diagnostic display to check for any other active fault codes related to the PTO switch, speed sensor circuits, or CAN bus communication to help pinpoint the issue.

2. 2

   Test PTO speed sensor

   Monitor the PTO speed reading via the diagnostic system while slowly rotating the front PTO shaft by hand. The reading should be stable. Disconnect the sensor and check its resistance with a multimeter (approximately 3000 Ohms). Replace if readings are erratic, zero, or infinite.

3. 3

   Test PTO solenoid

   Test the solenoid coil for continuity and correct resistance. If the solenoid clicks but the PTO doesn't engage, temporarily swap it with a non-critical solenoid on the tractor (e.g., differential lock) to see if the problem moves.

4. 4

   Perform hydraulic pressure test

   Check hydraulic pressure at the PTO clutch test port. Expected pressure is 17 to 21 bar (250 to 300 psi). Pressure below 15 bar indicates insufficient clamping force, pointing to a failing pump, regulating valve, or internal clutch leaks.

5. 5

   Replace faulty components

   Replace the speed sensor (ensuring correct air gap to the tone ring), solenoid valve/coil, or the front PTO clutch pack if hydraulic pressure is low and other causes are ruled out.

6. 6

   Clear codes and verify

   Clear the BCU fault codes and operate the front PTO to ensure the issue is resolved.