AIC 521128.02 – CommandQuad™ Range Switch BCDE Circuit Conflict. John Deere AIC System Alert.

AIC 521128.02 (AIC )

Code: 521128.02



This error code, AIC 521128.02, is activated when there is a conflict detected in the CommandQuad™ transmission range switch BCDE, where the ON and OFF contacts register the same value. This condition typically indicates a malfunction within the switch circuit, such as a short or a wiring issue, which prevents the control unit from distinguishing between the switch’s engaged and disengaged states.


In response to this conflict and to prevent potential transmission errors or mechanical damage, the control unit has automatically commanded the vehicle into a PARK position, which is recoverable once the issue is resolved.


  • Inspect the range switch BCDE for physical damage or signs of wear that could be causing the contacts to malfunction. Check for dirt, debris, or corrosion that might be causing the contacts to stick or fail.
  • Test the electrical continuity of the switch using a multimeter to ensure that the ON and OFF contacts are functioning independently as intended.
  • Examine the wiring and connectors leading to and from the switch for signs of damage, loose connections, or shorts that could be contributing to the issue.
  • Replace the faulty switch or repair any damaged wiring or components identified during the inspection. Ensure all connections are secure and properly insulated.
  • After making the necessary repairs, recalibrate the range switch settings if necessary and perform a system test to confirm that the switch is operating correctly and the vehicle can transition out of PARK mode without further issues.


Proper functioning of the transmission range switches is crucial for the reliable operation of CommandQuad™ transmissions. Regular maintenance and timely repair of these components are essential to ensure smooth operation and to avoid disruptions in vehicle performance.