John Deere 639.12 – TIQ: Vehicle CAN Bus (500 kBd), High Error Rate

Generated when the control unit detects an excessively high number of incorrect CAN Bus messages, or when it detects a general communication failure on the vehicle's CAN Bus network. This is typically caused by a short circuit, an open circuit, a failed terminating resistor, or excessive CAN Bus traffic overwhelming the network.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6105M
• 6125M
• 6140M
• 6150M
• 6170M
• 7210R-7290R
• 8225R-8400R

1. 1

   CAN Bus Resistance Test: Before opening connectors, measure the resistance across the CAN differential pair (CAN High and CAN Low pins) with the machine powered off. A healthy J1939/CAN backbone should read exactly 60 ohms. If it reads 120 ohms, one of the CAN bus terminating resistors is missing, failed, or there is an open circuit. If it reads near 0 ohms, there is a short circuit in the wiring.

2. 2

   Visual Wiring Inspection: Inspect the CAN Bus wiring harness and connectors between the TIQ module and the rest of the network for loose, damaged, or corroded pins.

3. 3

   Check for Interference: Ensure proper grounding and shielding of the CAN Bus cables, as electrical interference can disrupt communication.

4. 4

   Module Communication Check: Use a diagnostic scan tool (such as John Deere Service Advisor or Jaltest) to monitor CAN Bus messages and see which specific modules are failing to report.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical damage during testing.

2. 2

   Isolate the Fault

   Based on the resistance test, trace the CAN backbone. If the resistance was 120 ohms, locate the two CAN terminating resistors (often located in the roof panel, behind the instrument panel, or near the engine ECU depending on the model) and test them individually. Replace any resistor that does not read 120 ohms on its own.

3. 3

   Repair Wiring

   If a short or open circuit is found in the harness, repair the damaged section of the wiring or replace the affected harness segment. Ensure all connector pins are seated tightly and free of corrosion.

4. 4

   Check the TIQ Module

   If the wiring and resistors are intact (60 ohms present) but the TIQ module still reports a high error rate, the module's internal CAN transceiver may have failed.

5. 5

   Software Update / Reset

   Reconnect the battery. If the physical layer is repaired, perform a soft reset of the control module by cycling the power. If the code persists, connect a diagnostic tool to verify if the TIQ control software requires an update or re-calibration.