Optional second stage: factory ECU data over K-line, two 0–5V logging inputs, and digital AFR from a Spartan wideband.

K-Line, Aux & Wideband

Second stage — TuneFI tunes fine without any of this. These connectors add factory ECU data, arbitrary sensor logging, and digital AFR.

TuneFI has two DTM 3-pin connectors besides the main harness:

TuneFI aux connectors — DTM male: K-line (brown), AN1 0–5V (white), AN2 0–5V (green); Spartan UART: RX (red), TX (yellow), GND (black)

DTM male — K-line & aux inputs

Pin	Wire	Function
1	Brown	K-line — ECU data
2	White	AN1 — 0–5V analog input
3	Green	AN2 — 0–5V analog input

TuneFI ships the matching DTM 3-pin female connector and crimp pins so you can build your own pigtail.

Brown — K-line

K-line reads live sensor data from the motorcycle ECU — RPM, throttle, temps, manifold pressure, speed (and error codes, possibly more, in a future firmware). To plug into the bike's K-line connector you need one cheap bike-side connector, sold separately:

KLX300 — MWTPB-06-1A-R, e.g. on AliExpress. Located near the battery, on the left side of the bike.
KLX250 — Sumitomo HM 090, e.g. on AliExpress. Located near the muffler, on the right side of the bike.

MWTPB-06-1A-R connector kit — the bike-side K-line connector on the KLX300

Sumitomo HM 090 connector kit — the bike-side K-line connector on the KLX250

White — AN1

A general-purpose 0–5V input for logging. Example: an analog wideband controller that encodes AFR as a 0–5V voltage — configure TuneFI to convert it with the 2-point linear math in the app settings. (If you run a Spartan wideband, wire it digitally instead — see below.)

Green — AN2

A second 0–5V input, same deal. Log anything you can wire a sensor to.

DTM female — Wideband (Spartan)

The DTM 3-pin female connector is a UART that currently talks to one thing: the Spartan 3 v2 wideband controller. TuneFI polls it and gets AFR digitally — no voltage-to-AFR conversion guessing, readings as precise as the sensor allows.

TuneFI includes the matching DTM 3-pin male connector and crimp pins. Wire it to the Spartan 3 v2 (Lite):

TuneFI (female DTM)	Spartan 3 v2 Lite
Black — electronics ground	Black — electronics ground
Yellow — UART TX	Yellow — RX
Red — UART RX	Orange — TX

TX to RX, RX to TX — each side's transmit lands on the other's receive.

If AFR doesn't show up on the dashboard, polling is off. Go to Devices → AFR Sources → Spartan and switch polling on.

No Spartan? Any analog wideband works too — feed its 0–5V output into AN1 above and convert with the 2-point linear math in the app settings. Digital over UART is just better when you have it.