Commit the flash-day procedure doc (was written but never committed)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FP2GaxS9HkUdL5sLBnjKje

tunie/FLASH_DAY.md

@@ -0,0 +1,131 @@
+# Flash procedure — Arrow 2-1 + SAI/O2 delete
+
+Pull this up offline, no signal needed. Written 2026-09-08 for the Lonelec
+OBD2 adapter attempt. Checksum re-verified valid immediately before writing
+this doc — `computed=748a stored=748a MATCH`.
+
+## 0. The file
+
+**`tunie/research/reference-maps/derived/20262-arrow-delete-composed.hex`**
+
+- Base: `20262`, TuneECU's own official Arrow 2-in-1 calibration.
+- SAI + both O2 sensors disabled (device flags).
+- Two idle-mixture (Idle Fuel Trim/CO) bytes corrected toward richer.
+- Flash checksum patched and verified valid.
+- **What it is NOT**: the main VE fuel tables (the ones governing fueling
+  across the rev range) are untouched stock-Arrow calibration. This is the
+  correct, safe starting point — not a finished tune. Expect a wideband
+  pass later, not perfection today.
+- Safe to flash regardless of whether the O2 sensors are physically
+  installed or removed — SAI/O2-off is a software flag the ECU obeys
+  either way (see prior session notes if you want the full reasoning).
+
+## 1. Preconditions — confirm every one before connecting
+
+- [ ] Battery tender/maintainer connected (real smart tender, not a bare
+  trickle charger).
+- [ ] **Phone plugged into a charger and staying plugged in for the
+  entire session** — not just charged beforehand. TuneECU re-checks
+  phone battery live at the moment you tap reprogram (must be ≥16%, or
+  0%/failed-read, which also passes); a mid-session drain is what most
+  likely blocked a prior attempt, independent of the bike itself.
+- [ ] **Pull the headlight AND taillight fuses** — reduces electrical
+  load during the write, which matters more here than for a plain read:
+  a genuine ECU-side busy/reject (KWP negative response, NRC 0x21
+  `busyRepeatRequest`) is a real failure mode tied to voltage sag *under
+  load*, not resting voltage. Fuse numbers are bike-specific, check the
+  fusebox cover.
+- [ ] **Ignition on, engine off, kill switch in RUN position — confirmed
+  root cause (2026-09-09).** The "Unable to open programing session
+  (Battery low?)" / `ERR_PSESSION` error chased at length in an earlier
+  session turned out to be caused by the **kill switch being in the OFF
+  position**, not battery voltage, not the cable. Check this first,
+  before anything else on this list, if the error recurs — it's the
+  simplest and now-confirmed explanation.
+- [ ] Lonelec adapter connected and confirmed talking (see Step 2).
+- [ ] No other app/process holding the adapter's serial/BT channel.
+
+## 2. Confirm the link before touching anything programming-related
+
+Same principle as every prior session: prove the link is alive with the
+lightest possible check before risking a real operation.
+
+- Open TuneECU, connect via the Lonelec adapter, and get to a normal
+  **live diagnostics / read** screen first. Confirm you can read ECU ID
+  and current map info cleanly — this is the same "read" capability that
+  already worked with the old Bluetooth vLinker adapter, so it's a low
+  bar, not the real test.
+- If diagnostics don't come up clean, stop here. Don't proceed to
+  programming on a link that hasn't proven itself first.
+
+## 3. Read/backup the current map before writing anything
+
+- Use TuneECU's own **Read Map** to pull the bike's current calibration
+  and save it locally. This is your rollback reference and also confirms
+  end-to-end read capability on this exact adapter before you ever risk
+  a write.
+- Note the map ID it reports — should be a stock production/aftermarket
+  ID (20187/20191 family) unless it was already flashed.
+
+## 4. Load the tune file
+
+- In TuneECU, open **`20262-arrow-delete-composed.hex`** (the file from
+  Step 0).
+- Before writing, visually confirm in the app's map-info display:
+  - SAI: **off**
+  - O2 Sensor / O2 Sensor (2): **off**
+  - Checksum: should show valid (not flagged `*No-OEM`/`Error`) — if it
+    does show an error here despite our own `checksum.py` confirming
+    valid, stop and re-verify rather than overriding it.
+
+## 5. Reprogram
+
+- Tap reprogram. Expect TuneECU's standard confirmation dialogs
+  (write-caution / void-warranty) — confirm through them, that's normal.
+- **Do not disconnect the adapter, close the app, let the phone sleep,
+  or turn off ignition once the write actually starts.** A programming
+  session interrupted mid-write is the one genuinely bad outcome here —
+  everything upstream of this point has been reversible; this step is
+  not.
+- Watch for the "Battery low?" / `ERR_PSESSION` message specifically —
+  **check the kill switch is in RUN first** (confirmed root cause, see
+  Section 1). If it recurs with the kill switch already correct, new
+  adapter, phone charging, and fuses pulled, that's when to check bike
+  voltage *under load* (multimeter clipped on during the attempt) rather
+  than assume it's the
+  same cable issue as before.
+- Let it run to completion. Do not interrupt for anything short of a
+  genuine emergency.
+
+## 6. After a successful write
+
+- Read the map back and confirm the ID/checksum match what you just
+  flashed.
+- Check DTCs — some may appear immediately after a flash and clear
+  themselves on the next few ignition cycles; don't panic at one DTC
+  right after writing.
+- Idle the bike, listen/watch for anything obviously wrong (stalling,
+  extreme richness/leanness, warning lights) before riding it anywhere.
+- Turn ignition off, remove the tender, reinstall the fuses you pulled.
+
+## 7. If the write fails partway through
+
+- **Do not panic-disconnect further.** Per our own `RECOVERY_MODE.md`
+  research: TuneECU has a dedicated Recovery function specifically for
+  this — same underlying mechanism as a normal reprogram, gated by
+  whether the currently-loaded file decodes as valid (not by live ECU
+  state). If TuneECU offers "Run the ECU Recovery?", that's the
+  expected, designed-for path — not a sign everything is lost.
+- If recovery also fails to reach the ECU at all: this is exactly the
+  scenario `v-ladimir/audprog` (AUD debugger, SH705x un-brick via PCB
+  debug pins) exists for — a real, known backstop, not guesswork. Not
+  needed unless recovery mode itself can't establish contact.
+
+## Quick reference — exact paths
+
+```
+Tune file:  tunie/research/reference-maps/derived/20262-arrow-delete-composed.hex
+Checksum verify (if you want to re-check locally before flashing):
+  cd tunie/research/reference-maps
+  /Library/Frameworks/Python.framework/Versions/3.10/bin/python3.10 checksum.py derived/20262-arrow-delete-composed.hex
+```