Sources

Abbreviation	Source	Used for
ELM327DSJ	ELM327 datasheet “ELM327 OBD to RS232 Interpreter”, firmware v2.1, © Elm Electronics 2014, 94 pages. Original at Elm Electronics; retrieved 2026-10 via this copy. Pages according to the footer “N of 94”.	every AT command, response formats, timeouts, error messages (Command reference)
J1979	SAE J1979 / ISO 15031-5, diagnostic services for emissions-related systems (paid); details confirmed via the mode list in the datasheet (p. 31) and Wikipedia: OBD-II PIDs	modes, PID formulas, readiness (OBD-II services, PID formulas)
J2012	SAE J2012, structure of the trouble codes	P/C/B/U and four digits from two bytes
ISO 15765-2/-4	ISO-TP (splitting long messages) and OBD over CAN	frames, PCI, count byte (Response formats)
ISO 14229-1	UDS, negative responses (7F, reasons 11, 12, 21, 22, 78)	rejections
ISO 3779, ISO 3780, 49 CFR 565	VIN, WMI, check digit, model year	VIN decoding
OBDex	foerbsnavi/OBDex, data CC0-1.0	plain texts of the trouble codes
dtc-database	Wal33D/dtc-database, MIT, commit 04c43d7; origin of the texts not documented	optional, unverified online explanations (Explaining trouble codes online)
python-OBD	brendan-w/python-OBD, GPL-2.0, only in tests	comparison of the DTC and PID decoding
Traces	user logs from python-OBD, ELMduino, AndrOBD, sources per file in tests/fixtures/traces/	regression tests without hardware

The datasheet is only quoted and linked here, not republished. The quotes are short verbatim excerpts with page number.