John Deere 523773.03 – StarFire Receiver: CAN HI Voltage Too High

The StarFire GPS receiver has detected that the voltage on the CAN HI (High) communication circuit exceeds the acceptable normal operating range of 2.5 to 3.5 Volts. This over-voltage condition may affect the proper operation of connected components and typically indicates a short to a power source in the wiring harness or an internal fault within the receiver itself.

• Machines equipped with StarFire iTC
• Machines equipped with StarFire 3000
• Machines equipped with StarFire 6000

1. 1

   Record and clear fault codes to verify if 523773.03 is active and reappears immediately.

2. 2

   Visually inspect the wiring harness and 12-pin Deutsch connector at the StarFire receiver for pinched, frayed, or corroded wires.

3. 3

   Verify the machine's overall charging system voltage is within the normal range (12V to 14.4V) to rule out a general over-voltage condition.

1. 1

   Test CAN bus voltages

   Turn the key ON (engine off). Back-probe the connected 12-pin receiver connector. Measure DC voltage between Pin 4 (CAN High, Yellow) and Pin 7 (Ground, Black), then Pin 9 (CAN Low, Green) and Pin 7. Expected CAN High is 2.5V-3.5V; a reading significantly above 3.5V confirms the fault. Expected CAN Low is 1.5V-2.5V.

2. 2

   Isolate the fault

   Turn key OFF, disconnect the 12-pin harness, and inspect pins. Turn key ON and measure voltage at Pin 4 on the disconnected harness. If high voltage is present, the machine wiring has a short to power. If the high voltage disappears, the fault is likely internal to the receiver.

3. 3

   Test CAN bus resistance

   Turn key OFF and disconnect the vehicle battery. Measure resistance between Pin 4 and Pin 9 on the disconnected harness. Expected reading is approximately 60 ohms. A reading of 120 ohms indicates a missing terminating resistor or break; 0 ohms indicates a short circuit between CAN High and CAN Low.

4. 4

   Repair and verify

   Repair the affected wiring harness if a short or open circuit was found. If wiring and resistance tests are normal, replace the StarFire receiver. Reconnect all components, clear codes, and verify the fault does not return.