John Deere 1890.31 – RPT or BCU: PTO Shaft Spline Identifier Switch, Malfunction

Triggered when the control software detects an unexpected change in the rear PTO spline configuration reading while the rear PTO is actively engaged, indicating a malfunction, erroneous reading, or physical failure of the PTO shaft spline identifier switch (B179).

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6230
• 6330
• 6430
• 5080R
• 5090R
• 5100R
• 5080RN
• 5090RN
• 5100RN
• 6M-1654
• 6M-1854
• 6M-2104
• 1654
• 1854
• 2054
• 2104
• 6165J
• 6185J
• 6205J
• 6210J

1. 1

   Visually inspect the PTO shaft spline identifier switch (B179) at the rear PTO housing for physical damage, loose mounting, or disconnections.

2. 2

   Inspect the actual PTO spline for irregularities, debris, or physical damage that could prevent the switch from accurately identifying the spline configuration.

3. 3

   Inspect the wiring harness and electrical connections routed to the B179 switch for signs of wear, corrosion, damaged insulation, or loose connections.

4. 4

   Use Service ADVISOR to monitor live data from the spline identifier switch to verify it correctly identifies various spline configurations and does not drop the signal.

5. 5

   Verify that the RPT or BCU control software is updated to the latest version, as patches are sometimes released to address overly sensitive switch logic.

1. 1

   Preparation

   Ensure the tractor engine is off, the key is removed, and the rear PTO is fully disengaged.

2. 2

   Access the Switch

   Locate the B179 PTO Shaft Spline Identifier Switch on the rear PTO housing.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical harness connector from the switch. If the connector is corroded, clean it with electrical contact cleaner.

4. 4

   Remove the Faulty Switch

   Unbolt or unthread the faulty switch from its mounting point on the PTO housing.

5. 5

   Install the New Switch

   Install the replacement spline identifier switch. Ensure it is securely mounted and seated correctly so it can accurately read the spline.

6. 6

   Reconnect and Calibrate

   Reconnect the electrical harness. If required by your specific model's service manual, use a diagnostic tool to recalibrate the new switch so the BCU/RPT learns its baseline parameters.

7. 7

   Clear Codes and Test

   Reset the BCU/RPT to clear the 001890.31 diagnostic trouble code. Start the tractor, engage the rear PTO safely, and conduct an operational test to ensure the code does not return.