Often, the D1A code appears simply because the DEF tank was run low, and the sensor lost its reference.
While less common, air pockets near the quality sensor during priming can cause a momentary invalid data reading. john deere d1a code
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. Often, the D1A code appears simply because the
Subject: Engine Control Unit (ECU) Diagnostic Trouble Code (DTC) Category: Engine / Fuel System Severity: High (Active derate likely) it cannot read any key