pacifica-obd OBD-II / UDS diagnostics toolkit
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pacifica-obd#

A command-line OBD-II and UDS diagnostics toolkit for a 2021 Chrysler Pacifica, talking to a vLinker FS USB adapter. Built on python-OBD, managed with uv, scriptable end to end.

Generic OBD-II reads are the tested core. The same adapter is then driven at the raw ELM327/STN level for UDS work: module discovery, all-module DTC reads and identification DIDs on either CAN bus — plus a deliberately guarded write path you have to opt into explicitly.

sh
uv sync
uv run pacifica-obd scan      # VIN + stored codes + supported PIDs

Get started Command reference

macOS · Python 3.12+ via uv · MIT · not affiliated with Stellantis

What this can and can't do here#

Task Support How
VIN, stored and pending codes, readiness monitors, live data, freeze frame ✅ Generic OBD-II: scan, dtc, readiness, watch, freeze
Codes from the other modules that answer on CAN-C / CAN-IHS ✅ read-only dtc-all — raw codes and status flags, no text descriptions
Part, software and hardware numbers per module ✅ read-only module-info, read-did (F187–F191)
Which modules should exist, and at which addresses ✅ read-only module-map (plus an optional read-only external ECU database)
Clear engine codes ⚠️ dtc --clear sends mode 04. The Security Gateway may refuse it, and it erases freeze frames and readiness history
Write a DID (2E) or run a routine (31) ⚠️ experimental Guarded behind --confirm, not reversible by this tool, usually refused by the SGW
Coding, adaptations, module programming ❌ Beyond those primitives. Use Appcar DiagFCA / JScan / dealer wiTECH, with an SGW bypass

What it does#

  • Check-engine basics

    VIN, stored (mode 03) and pending (mode 07) codes, permanent codes when the installed python-OBD exposes mode 0A, readiness monitors, and the freeze frame behind a fault.

  • Live dashboard

    watch RPM, speed, coolant, load, throttle, intake temp, MAF and fuel level. Log every sample to CSV, or stream newline-delimited JSON into jq.

  • Every module, not just the PCM

    dtc-all discovers the modules that answer on one or both CAN buses, then asks each of them for its codes over UDS 19 02.

  • Who is on the bus

    modules finds the responders, module-info reads their part and software/hardware numbers, and module-map shows which modules should exist and at which addresses.

  • History that stays local

    Every run lands in a local SQLite database plus an append-only JSONL log, so this week's codes can be compared with last month's. Nothing is uploaded.

  • TUI or JSON

    Browse with the keyboard/mouse in tui, or put --json on any read command for scripts, spreadsheets and CI.

Read-only by default — and park the van

Discovery and dtc-all put each module into an extended diagnostic session (10 03) while they read. Run them parked, with the ignition ON. Nothing writes unless you ask it to: the write services (dtc --clear, write-did, routine) are gated behind an explicit confirmation, and security only asks for a seed — no seed→key provider is configured, so nothing is unlocked.

On a 2021 Pacifica the Security Gateway blocks writes on the stock port, so expect a write to be refused without a 12+8 bypass cable. See the Security Gateway deep dive.

Deep dives#

  • Chrysler Security Gateway

    What the SGW is, what it blocks on a 2021, when a 12+8 bypass cable is needed, and where Appcar / JScan / wiTECH fit.

  • Enhanced (manufacturer-aware) diagnostics

    How manufacturer-aware tools actually work, what this adapter can already do, and the roadmap from generic OBD-II to UDS.

  • Vehicle support (RU family)

    Other model years, the Voyager and Grand Caravan, and the PHEV: what is known to carry over and what still has to be mapped.

  • Technical reference

    Architecture, ISO-TP/UDS notes, the +8 versus −0x280 addressing rule, bus presets, and the storage model.

MIT licensed — see the repository's LICENSE.