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Diagnostic comparisons

Compare OBD codes and concepts

P0420 vs P0430

Upstream vs downstream O2 sensor

Bank 1 vs Bank 2

OBD1 vs OBD2: scope

Diagnostic knowledge search

23,879 code identifiers with scoped meanings, and 54,261 enhanced signal definitions. No VIN or personal information is needed.

Diagnostic explainers

Pending, stored and permanent codes · Enhanced PIDs and Mode 22

23,879 matches

Page 487 · 14581–14610 shown
C056D
Electronic Control Unit Hardware; Electronic Control Unit Hardware Signal Erratic; Electronic Control Unit Hardware Low Signal Amplitude; Electronic Control Unit Hardware Internal Checksum Error; Electronic Control Unit Hardware General Memory Malfunction; Electronic Control Unit Hardware Special Memory Malfunction; Electronic Control Unit Hardware RAM Malfunction; Electronic Control Unit Hardware ROM Malfunction; Electronic Control Unit Hardware EEPROM Performance/Malfunction; Electronic Control Unit Hardware Software Malfunction; Electronic Control Unit Hardware Internal Malfunction; Electronic Control Unit Hardware Incorrect Component Installed; Electronic Control Unit Hardware Self-Test Malfunction; Electronic Control Unit Hardware Internal Communication Malfunction; Electronic Control Unit Hardware EEPROM Incorrect Programming

1 reference families · GM

C056E
Electronic Control Unit Software; Electronic Control Unit Software Supervision Software Malfunction; Electronic Control Unit Software Not Programmed; Electronic Control Unit Software Calibration Not Programmed; Electronic Control Unit Software EEPROM Incorrect Programming; Electronic Control Unit Software Variant Not Programmed; Electronic Control Unit Software Configuration Not Programmed; Electronic Control Unit Software VIN Not Programmed; Electronic Control Unit Software Security Code Not Programmed; Electronic Control Unit Software Programming Checksum Error; Electronic Control Unit Software Calibration Not Learned; Electronic Control Unit Software Not Plausible; Electronic Control Unit Software Invalid Data

1 reference families · GM

OBD Lens reference library · catalog legacy-owner-2026-11-02-v84-evidence. Sources and scope