Fendt B038 – Engine Control Unit (ECU) / EDC / EMR: Position Sensor EST Match Failure

The system has detected a mismatch or plausibility error between the two redundant potentiometers located in the foot throttle sensor assembly (B055 combi-sensor). One signal provides engine speed control via the EDC/EMR, while the other is used by the Tractor Management System (TMS). If the control units detect differing voltage values between these two potentiometers, a plausibility error is triggered. This issue is associated with the automatic maximum output control function in the EMR Engine control system.

• 300 Vario
• 400 Vario
• 500 Vario S4
• 700 Vario
• 800 Vario
• 900 Vario

1. 1

   Visually inspect the wiring harness and connectors between the foot throttle sensor (B055) and the control units (A050 Basic Control Unit and A099 Engine Control ECU) for any visible damage, corrosion, or loose connections.

2. 2

   Test power supply at sensor connector X898 with ignition ON: Pin 2 (+UB) should measure 8.5 V DC (if incorrect, check microfuse S19 in the A013 PCB or wiring). Pin 5 (+UB) should measure 5.0 V DC (if incorrect, check A099 ECU or wiring). Pins 1 & 4 should have good continuity to ground.

3. 3

   Test signal voltage at sensor connector X898: Signal Pin 3 (to Earth Pin 1) should measure ~4.0 V DC when not actuated and ~1.0 V DC when fully actuated. Signal Pin 6 (to Earth Pin 4) should measure ~0.6 V DC when not actuated and ~4.3 V DC when fully actuated.

4. 4

   Test signal current at A050 Basic Control Unit (EXT) separation point X1402, Pin #B18: Should measure ~19 mA DC when not actuated and ~5 mA DC when fully actuated.

1. 1

   Replace foot throttle assembly

   If diagnostics confirm a faulty sensor, replace the entire foot throttle assembly (B055 combi-sensor). It is a single unit containing the redundant potentiometers, secured by four bolts with a single electrical connector.

2. 2

   Calibrate new sensor

   Navigate to the service/diagnostics menu on the tractor's terminal and enter Calibration Code 4005. Follow the on-screen prompts to teach the control units the new sensor's voltage range for idle and full throttle positions. Failure to calibrate will result in continued incorrect operation.