Fendt 05.1.59 – A050 - ECU, basic control unit: S086 - Switch, brake wearing, right: Sensor faulty, Signal fault

This code indicates an electrical issue—such as an open circuit, short circuit, or out-of-range resistance—originating from the right-hand brake wear indicator switch. This code specifically flags a sensor/signal failure.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt 300 Vario series
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series (e.g., COM III, SCR models)

1. 1

   Check Reference Voltage: The A050 basic control unit supplies a basic signal voltage of 6.0 VDC to the switch.

2. 2

   Measure Signal Voltage/Resistance: Depending on the position of the switch, the internal resistance drops the voltage. Measure the signal voltage at Pin 1 and Pin 2 of the switch connector with the ignition ON. Switch Open (Brake pad OK): approx. 510 Ohms, ~3.7 VDC. Switch Closed (Brake pad worn): approx. 121 Ohms, ~1.7 VDC. Fault Condition: If the switch or wiring is completely open (infinite resistance), the signal voltage will read the full reference voltage (approx. 6.1 VDC to 8.0 VDC).

3. 3

   Wiring Inspection: Inspect the wiring harness between the S086 switch and the A050 ECU for breaks, chafing, or corroded pins.

1. 1

   Safely park the tractor, engage the parking brake, and turn off the ignition.

2. 2

   Locate the S086 right brake wear switch on the right-hand rear axle/brake housing assembly.

3. 3

   Disconnect the electrical connector from the switch.

   Inspect the terminals for moisture, dirt, or corrosion. Clean if necessary.

4. 4

   Using a multimeter, test the resistance across the pins of the sensor itself.

   If the sensor reads an open circuit (infinite Ohms) or a dead short (0 Ohms) instead of the specified 510 Ohms (normal state), the internal resistor has failed.

5. 5

   Unbolt/unscrew the faulty S086 switch from the brake assembly and install the replacement part.

6. 6

   Reconnect the wiring harness securely.

7. 7

   Turn the ignition on and use the tractor's terminal/multifunction armrest (MFA) to call up the fault memory and clear the stored 05.1.59 code from the A050 ECU.