John Deere 3420 Tractor Error Codes

Customer access; recall, record, and clear diagnostic trouble codes:

Press and hold the roll mode switch for 5 seconds to begin diagnostic session. Upon entering diagnostics, any active or previously active codes automatically appear in a scrolling fashion with each one showing the control unit (3 letter abbreviation) and the code number (XXXXXX.XX). To view and/or clear diagnostic trouble codes for any given control unit, do the following:

1. Use the right turn signal switch to scroll to the desired control unit.
2. Press and release the roll mode switch to enter the diagnostic addresses for that desired control unit.
3. Use the right turn signal switch to scroll to diagnostic address 001 for that desired control unit.
4. If codes are present the word "codes" appears. If not, the word "none" appears.
5. Press and release the roll mode switch to view all code details for this control unit.
6. Any codes present in that control unit appears there in scrolling fashion for multiple codes.
7. To access the option for clearing codes for this selected control unit, press and release the right turn signal switch.
8. The question "CLR ?" appears.
9. To clear the codes, press and release the roll mode switch.
10. To go back to the entire control unit list, press and release the left turn signal switch.