John Deere 523773.04 – StarFire / DTI: CAN HI Voltage Too Low

The control module has detected that the voltage on the CAN (Controller Area Network) High communication circuit is below the acceptable threshold (typically under 2.5 volts). The CAN bus is a critical communication network that allows various electronic control units (ECUs) to exchange information. A low voltage condition on the CAN High line can disrupt this communication, which may affect the proper operation of connected components and lead to malfunctioning systems.

• StarFire 3000
• StarFire 6000
• 6230 Premium
• 6330 Premium
• 6430 Premium
• 6170R
• Air Carts

1. 1

   Review the display for any other active fault codes, as multiple communication codes can indicate a widespread network issue

2. 2

   Power cycle the machine (turn ignition off, wait, then turn back on) to see if the code is intermittent

3. 3

   Visually inspect the entire CAN bus wiring harness, paying close attention to the yellow (CAN High) and green (CAN Low) wires for chafing, pinching, corrosion, or breaks

4. 4

   Check all related CAN connectors (StarFire receiver, implement breakaway, inline connections) to ensure they are clean, free of corrosion, and securely latched

5. 5

   Perform a CAN Bus Resistance Test with Key OFF and battery disconnected: measure between CAN High and CAN Low. Expected reading is approximately 60 Ω. A reading of 120 Ω indicates a missing or failed terminator, 0 Ω indicates a short circuit, and Open/OL indicates an open in the wiring

6. 6

   Perform a CAN Bus Voltage Test with Key ON: measure CAN High to ground (expected 2.5-3.5V) and CAN Low to ground (expected 1.5-2.5V)

1. 1

   Address resistance test findings

   If the resistance check shows 120 Ω, inspect both ends of the CAN bus and install or replace the missing/faulty terminating resistor. If the resistance is 0 Ω, locate and repair the short circuit using visual inspection or the split-half method (disconnecting sections of the harness).

2. 2

   Address voltage test findings

   If the CAN High voltage is low but the resistance test was normal (60 Ω), check for a short to ground specifically on the CAN High wire or a faulty controller pulling the voltage down.

3. 3

   Isolate the fault

   If wiring and terminators appear good, unplug controllers from the CAN bus one at a time while re-checking voltage and resistance. The module (or its pigtail harness) that causes readings to return to normal when unplugged is the source of the problem.

4. 4

   Repair and verify

   Repair any damaged wiring using appropriate splicing/sealing methods, replace corroded connectors, or replace the faulty terminating resistors/control modules identified. Clear all fault codes and operate the machine to verify the issue is resolved.