Case IH PAF – Transmission Control Module (TCM) / Electronic Control Unit (ECU): Vehicle CAN Chip, Data Incorrect

Code tAF indicates a communication breakdown on the tractor's Controller Area Network (CAN) bus. Specifically, it means the CAN chip inside the control module is receiving or transmitting invalid/incorrect data.

• MXM
• Case IH MXM120
• Case IH MXM130
• Case IH MXM140
• Case IH MXM155
• Case IH MXM175
• Case IH MXM190
• Case IH Magnum Series
• Case IH Puma Series
• Case IH MX Magnum 180
• Case IH MX Magnum 200
• Case IH MX Magnum 220
• Case IH MX Magnum 240
• Case IH MX Magnum 270

1. 1

   Check for related codes like tB0, tB1, or tB2/tB3 which indicate a hard wiring short rather than a failed module

2. 2

   Verify alternator output and clean main chassis grounds, as low battery voltage or poor cab grounds can cause the CAN chip to drop data packets

3. 3

   Inspect the CAN bus wiring harness leading to the Transmission ECU for rodent damage, chafing, or melted wires

4. 4

   Disconnect the Transmission ECU and inspect the pins for pushed-back pins, water intrusion, or green corrosion

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the TCM

   Locate the Transmission Control Module (usually located under the right-hand console or cab floor, depending on the exact model).

3. 3

   Clean and Reseat

   Spray the harness connectors and the ECU pins with electrical contact cleaner. Reseat the connectors firmly.

4. 4

   Clear Codes

   Reconnect the battery. Use the Case IH Electronic Service Tool (EST) or the tractor's H-Menu diagnostic mode to clear the fault codes.

5. 5

   Test the CAN Bus

   Turn the key to the "ON" position. If the tAF code returns immediately, the internal CAN chip on the Transmission ECU has failed and the module must be replaced.

6. 6

   Replace and Calibrate

   If replacing the ECU, install the new module. You must perform a Transmission/EDC Calibration setup procedure.