CLAAS Id788Ch / 788Ch – EXT (A62) / ISO 7-pin ECU (A101): Invalid Rear Power Take Off Speed Information

The EXT external function module has not received speed information from the rear PTO for more than 5 seconds (BUS CAN), or the PTO speed information is not available over the 7-pin ISO connector.

• CLAAS Axion 810
• CLAAS Axion 850
• CLAAS Axion 920
• CLAAS Axion 950
• CLAAS Arion 510-640 series

1. 1

   Check the CLAAS vehicle CAN bus network for short-circuits or open circuits in the communication lines

2. 2

   Check the 7-pin ISO connector at the rear of the tractor for corrosion, pushed-out pins, or physical damage

3. 3

   Check the PTO Speed Sensor operating conditions, resistance, supply voltage, and ground

4. 4

   Check related modules, including the bus CAN network communication module BDG (A103) and the TR3 (A57-3) transmission module

1. 1

   Visual Inspection

   Start at the rear of the tractor. Inspect the 7-pin ISO connector and the wiring harness leading to the PTO speed sensor. Look for chafed wires or broken connectors.

2. 2

   Clean and Secure Connections

   Disconnect the 7-pin ISO connector, clean the contacts with electrical contact cleaner, and reconnect securely.

3. 3

   Test the Sensor

   Using a multimeter, test the PTO speed sensor for continuity and correct resistance values as per the measurement files. Check for a 5V/12V reference supply (depending on the specific sensor generation) and a good ground.

4. 4

   Replace Faulty Components

   If the sensor fails the resistance/output test, replace the PTO speed sensor. If the 7-pin ISO connector is physically damaged or heavily corroded, splice in a replacement plug/socket.

5. 5

   Clear and Verify

   Connect the CLAAS Diagnostic System (CDS), clear the fault memory, start the tractor, and engage the rear PTO. Increase engine speed between 1000 and 1500 rpm to verify that the PTO speed information is now successfully broadcasting over the CAN bus.