John Deere 000190.31 – RPT: Missing Engine Speed CAN Message

A communication breakdown has occurred on the Power Train CAN bus network. The Rear PTO Control Unit (RPT) or another powertrain controller is expecting to receive an engine speed message from the Engine Control Unit (ECU), but this message is missing or not valid. This prevents systems relying on engine speed data from functioning correctly.

• 6M
• 6R
• 7R
• 8R

1. 1

   Check for other active fault codes, especially CAN communication codes (FMI 9) or ECU-specific faults, which can provide clues to the problem's location.

2. 2

   Visually inspect wiring harnesses and connectors for the Power Train CAN bus, ECU, and RPT for chafing, pinched wires, rodent damage, or corrosion.

3. 3

   Verify clean and stable power and solid ground connections to the ECU and RPT controllers.

4. 4

   Enter diagnostic mode (if equipped) to verify individual switch and sensor inputs to the control modules.

1. 1

   Power down machine

   Turn the main key switch to the OFF position and disconnect the battery before performing any resistance checks on the CAN bus.

2. 2

   Check CAN bus resistance

   Measure resistance between the CAN High (yellow wire) and CAN Low (green wire) pins at a diagnostic connector. The expected value is approximately 60 ohms. A reading of 120 ohms indicates a missing or failed terminating resistor. A reading significantly lower than 60 ohms indicates a short circuit between the CAN wires, and an open-loop reading indicates a break in the wiring.

3. 3

   Inspect terminating resistors

   If the resistance reading is incorrect, locate the terminating resistors at the physical ends of the main CAN bus harness (typically one at the front and one at the rear). Test each resistor individually to ensure it reads 120 ohms.

4. 4

   Check CAN bus voltages

   Reconnect the battery and turn the key switch ON (engine off). Measure DC voltage between CAN High and chassis ground (expected 2.5 to 3.0 volts), and CAN Low to chassis ground (expected 2.0 to 2.5 volts). Incorrect voltages point to a short to power or ground in the wiring or a chattering controller.

5. 5

   Isolate faulty controller

   If wiring and terminators are good but the fault persists, unplug controllers from the Power Train CAN bus one at a time (starting with the RPT on the rear chassis), cycle the key, and check if the fault code clears. The last controller disconnected when the code disappears is likely the source.

6. 6

   Update software or replace controller

   If all wiring and components test correctly, a software update by a dealer may be necessary. If a specific controller is identified as faulty and cannot be repaired via software update, replace it.