Onboard diagnostics are a core part of John Deere’s service strategy. They provide fast, accurate data that helps isolate issues at the module, sensor, or circuit level. By learning to interpret the meaning behind a prefix and code, you can reduce repair time and improve reliability.

Here are five additional John Deere fault codes and how to solve them effectively.

Fault Code: PTQ 524021.14 – Gear Command Acknowledgment Timeout

Prefix System: PTQ – PowrQuad Transmission Controller
Function: Manages gear shifting logic in PowrQuad tractors

Code Meaning:
The controller sent a gear change command but did not receive confirmation, typically due to actuation failure or mechanical blockage.

Common Causes:

• Sticky or slow gear actuator
• Failed or unplugged feedback sensor
• Hydraulic pressure too low to complete shift

Troubleshooting Tips:

1. Use diagnostics to confirm gear position sensor activity.
2. Command gear shifts manually and monitor real-time response.
3. Inspect shift actuator and electrical connections.
4. Check transmission oil quality and pressure.
5. Replace the actuator or perform internal inspection if gear changes consistently fail.

Fault Code: PLC 523811.31 – Park Lock Engagement Sensor No Signal

Prefix System: PLC – Park Lock Control
Function: Controls the electronic and hydraulic park lock solenoids and monitors their position

Code Meaning:
The system did not receive a valid position signal confirming park lock engagement, preventing proper operation.

Common Causes:

• Faulty or dirty sensor
• Mechanical blockage in linkage
• Wire break in sensor harness

Troubleshooting Tips:

1. Inspect the park lock position sensor and bracket.
2. Manually engage/disengage the park lock and watch for changes in diagnostics.
3. Test continuity between sensor and PLC module.
4. Clean sensor and tone ring if equipped with magnetic pickup.
5. Replace the sensor if readings are fixed or missing.

Fault Code: CCU 524048.07 – Differential Lock Switch Stuck On

Prefix System: CCU – Chassis Control Unit
Function: Oversees core drivetrain functions including diff lock, alarms, and fuel level

Code Meaning:
The differential lock switch is reporting constant activation, preventing normal disengagement or causing traction control issues.

Common Causes:

• Physically stuck or damaged switch
• Moisture inside cab switch panel
• Signal wire shorted to ground

Troubleshooting Tips:

1. Toggle the diff lock switch and observe live status.
2. Inspect the switch for mechanical return.
3. Unplug the switch to see if the signal clears.
4. Check for continuity between signal wire and ground.
5. Replace the switch if it continues to signal falsely.

Fault Code: SV3 641.06 – Hydraulic Valve Coil Voltage Low

Prefix System: SV3 – Selective Control Valve 3
Function: Operates rear SCV #3 for implement hydraulics

Code Meaning:
The SCV 3 coil is receiving insufficient voltage, which may prevent proper hydraulic movement or lead to sluggish spool response.

Common Causes:

• Weak coil or excessive internal resistance
• Undervoltage during high electrical load
• Loose connector at valve block

Troubleshooting Tips:

1. Check supply voltage at the coil connector during valve activation.
2. Test coil resistance with a multimeter.
3. Inspect fuse panel and voltage distribution to the hydraulic system.
4. Wiggle the harness while monitoring coil voltage for intermittent drops.
5. Replace the coil if it shows weak magnetism or voltage draw.

Fault Code: TEC 523211.31 – ISOBUS Implement Not Responding

Prefix System: TEC – Tractor Equipment Controller
Function: Coordinates communication between the tractor and connected ISOBUS implements

Code Meaning:
The tractor has failed to establish communication with an attached ISOBUS implement, often due to wiring or ECU issues.

Common Causes:

• Damaged ISOBUS connector or pins
• Implement ECU not powered or malfunctioning
• CAN bus conflict on the implement side

Troubleshooting Tips:

1. Inspect ISOBUS connector on both tractor and implement.
2. Use another implement to verify if the issue is on the tractor or implement side.
3. Test voltage and CAN signals at the ISOBUS terminal.
4. Look for bent or missing pins in the connector.
5. Update or reprogram implement ECU firmware if communication fails consistently.