The antenna ring around the ignition switch reads the key’s chip. If this ring is cracked, corroded, or unplugged, it cannot read any key, leading to D1A 01.
Engine Control Unit (ECU) Diagnostic Trouble Code (DTC) Category: Engine / Fuel System Severity: High (Active derate likely) john deere d1a code
Once in D1A, you can cycle through different diagnostic options using the turn signal lever or specific dashboard buttons. The antenna ring around the ignition switch reads