Wideband O2

A wideband is how you tune VE. A narrowband is how you keep a catalytic converter happy at stoich — it is not a tuning tool. Fit a wideband before you start mapping.

CAN wideband (preferred)

A CAN controller (Race Core / rusEFI wideband, some AEM and similar) puts lambda on the bus with no analog scaling fights. Wire CAN H/L, power the heater from the main-relay 12 V with its own fuse, terminate the bus correctly. Enable the matching CAN channel in TunerStudio.

Analog 0–5 V

If the controller only has an analog out, take it to a spare AV (often AV 5). Enter the controller’s published volts-to-AFR or volts-to-lambda curve. Do not assume 0 V = 10:1 and 5 V = 20:1 — that is one common scale among many.

• Heater 12 V from the main relay, fused. Never from 5 V Sens.
• Analog ground to sensor GND, not the exhaust.
• Bung in the collector, pre-cat, 10°–45° from vertical so condensation does not sit on the element. Not in a single header primary unless you like cylinder-1 AFR and a lie.