Fendt 6.1.60 – A004 ECU (Control Panel / Actuator Unit): Plausibility error between the PTO clutch RPM and the PTO stub shaft speed

The system has detected that the actual speed of the rear PTO stub shaft (monitored by sensor B020) differs by more than ±12% from the setpoint speed of the PTO clutch (monitored by sensor B021).

• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• Farmer 400 Vario series (409, 410, 411, 412, 413, 414, 415)
• Favorit / Vario 700 series (711, 712, 714, 716, 718)
• Vario 800 series (815, 817, 818, 820, 822, 824, 826, 828)
• Favorit / Vario 900 series (916, 920, 924, 926, 927, 930, 933, 936, 939 - including COM III and S4 generations)

1. 1

   Perform an Emergency Mode Test by pressing and holding the 'Engage PTO' button for more than 5 seconds. If electric speed selection remains possible, the issue is likely a sensor signal fault. If it cannot be engaged, suspect a faulty or seized solenoid valve.

2. 2

   Inspect the sensor wiring harnesses and separation points (X169 for B020 and X170 for B021) near the PTO stub shaft for corrosion, chafing, or loose pins.

3. 3

   Verify the 12V supply, ground, and signal output of the B020 and B021 Hall-effect sensors using a multimeter or oscilloscope while the PTO is turning.

4. 4

   Inspect the PTO control block solenoid valves (Y026, Y027, Y028) for proper coil resistance, ensure they receive voltage when a speed is selected, and check if internal spools are mechanically seized.

1. 1

   Safely secure the tractor

   Park on level ground, turn off the engine, and remove the key.

2. 2

   Access the rear PTO sensors

   Remove the rear cover panels near the PTO stub shaft to access the B020 (stub shaft) and B021 (clutch) sensors.

3. 3

   Replace faulty sensors

   If diagnostics point to a sensor failure, disconnect the wiring harness (X169/X170), unbolt the faulty Hall-effect sensor, and install the replacement. Torque to OEM specifications.

4. 4

   Service the solenoid valves (if applicable)

   If the emergency mode test failed to engage the PTO, locate the PTO valve block. Disconnect the electrical connectors for Y026, Y027, and Y028. Unbolt the suspect valve. If it is mechanically seized with debris, clean the valve block and replace the solenoid valve.

5. 5

   Reassemble and clear codes

   Reconnect all harnesses, reinstall cover panels, and use the FENDIAS diagnostic tool (or the tractor's onboard terminal) to clear the 6.1.60 fault code.

6. 6

   Test operation

   Start the tractor and engage the rear PTO at different speed selections (540, 750, 1000) to verify the plausibility error does not return.