# 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
```