John Deere 000524.09 – SSU: Selected Gear Message Missing

The Steering System Control Unit (SSU) is not receiving the 'Selected Gear Message' from the transmission controller over the Controller Area Network (CAN) bus. This message communicates the position of the reverser lever and the currently selected gear. The loss of this data prevents proper coordination between the tractor's steering and transmission systems, which is critical for advanced features like AutoTrac.

• 9230
• 9330
• 9430
• 9530
• 9630
• 8310RT
• 8335RT
• 8360RT
• 7210J
• 6230
• 6330
• 6430
• 7130
• 7230
• 7330

1. 1

   Restart the vehicle to see if a temporary communication glitch resolves the issue

2. 2

   Check fuse F6 (for tractors with AutoPowr or IVT transmissions)

3. 3

   Check fuse F35 (for tractors with PowrQuad Plus transmissions)

4. 4

   Check fuse F23 (for the SSU unswitched power supply on some models)

1. 1

   Visual Inspection

   Thoroughly inspect the wiring harness and connectors between the SSU and the transmission controller (EPC). Look for signs of damage such as chafing, corrosion on pins, pinched wires, or loose connections. Pay close attention to connectors on the frame and those leading to the controllers under the cab.

2. 2

   CAN Bus Resistance Check

   Power down and disconnect the vehicle's battery. Access the 9-pin diagnostic connector and measure resistance between Pin C (CAN High) and Pin D (CAN Low). A healthy CAN bus should read approximately 60 Ohms. A reading of 120 Ohms suggests a missing terminating resistor or open circuit. 0 Ohms indicates a short circuit. A high/fluctuating reading points to a significant break in the wiring.

3. 3

   CAN Bus Voltage Check

   Reconnect the battery and turn the key to the 'On' position without starting the engine. Measure the DC voltage of the CAN lines relative to a good chassis ground. CAN High (Pin C) should be between 2.5 and 3.0 Volts. CAN Low (Pin D) should be between 2.0 and 2.5 Volts. Abnormal voltages indicate a short to power/ground or a faulty transceiver.

4. 4

   Isolate the Fault

   If resistance or voltage readings are incorrect, use the 'split-half' method. Disconnect a central controller on the CAN bus to electrically split it, then re-measure resistance on one half. A reading of 120 Ohms indicates that half of the network is likely good. Continue disconnecting controllers one by one until the faulty component or wiring section is identified.

5. 5

   Controller Replacement

   If wiring and terminating resistors are confirmed to be good, the issue may lie with either the SSU or the EPC controller. Replace the suspected controller after isolation testing confirms it is disrupting the network.