CLAAS Id76ACh / 76ACh (723) – REH (A58) lifting module: Missing or Erroneous Lifting Position Instruction on Powertrain CAN Bus

The REH (A58) lifting module receives no lifting position instruction information, or this information is in error on the Powertrain CAN bus. As a direct consequence, the tractor's rear lifting function is locked out for safety, and the system defaults to requiring the use of external controls.

• Axion 850
• Axion 840
• Axion 830
• Axion 820
• Axion 810
• Axion 950
• Axion 940
• Axion 930
• Axion 920
• Arion 640
• Arion 630
• Arion 620
• Arion 610
• Arion 540
• Arion 530
• Arion 520
• Arion 510
• Arion 430
• Arion 420
• Arion 410

1. 1

   Check the Powertrain CAN bus network to verify communication lines are intact

2. 2

   Check the CLAAS vehicle CAN bus network for short-circuits to ground or open circuits

3. 3

   Check the lifting position instruction potentiometer (R77) to verify the physical knob/sensor on the armrest is outputting the correct signal voltage

4. 4

   Check the MFA (A100) armrest multifunction module to ensure it is receiving the potentiometer signal and broadcasting it to the CAN bus

5. 5

   Check the lifting module REH (A58) to ensure the module is online and receiving CAN messages

6. 6

   Check harnesses and connectors for each component, verifying continuity, sources of energy (fuses, power supply, ground), and looking for short or open circuits

1. 1

   Bypass for immediate use

   Since the in-cab lifting is locked, use the external fender controls to lower or raise the implement safely before beginning diagnostics.

2. 2

   Inspect Wiring

   Visually inspect the wiring harness connecting the R77 potentiometer to the MFA (A100) armrest module. Look for pinched wires or loose connector pins.

3. 3

   Test the R77 Potentiometer

   Measure the resistance and signal voltage of the lifting position instruction potentiometer (R77). If the voltage is out of range (too high/too low), the potentiometer is faulty and must be replaced.

4. 4

   Test CAN Bus Integrity

   Using a multimeter or CAN bus diagnostic tool, check the Powertrain and Vehicle CAN bus lines between the MFA (A100) and the REH (A58) modules. Ensure CAN-High and CAN-Low voltages are within specification (typically ~2.7V and ~2.3V respectively).

5. 5

   Module Verification

   If the wiring and potentiometer are good, check the power and ground supplies to the MFA (A100) and REH (A58) modules. If a module has proper power/ground but fails to transmit or receive the position instruction data, replace the faulty module.

6. 6

   Calibration

   If the R77 potentiometer, MFA (A100), or REH (A58) is replaced, check if compatibility programming, settings adjustments, or calibrations are required via the CLAAS Diagnostic System (CDS).