What a narrowband sensor can and can't do
A narrowband sensor only reads accurately in a small band around stoichiometric, about 14.7:1 AFR on gasoline. Its output swings sharply from rich to lean right at that point, which is exactly what a catalytic converter needs: the factory ECU keeps the mixture flipping just either side of stoich so the cat works efficiently. Away from stoich, the reading is close to useless.
That makes a narrowband fine for two jobs on an Elite: logging and monitoring, and closed loop O2 Control around stoich at idle and cruise. For tuning fuel tables, especially under load, you need a wideband. A Haltech WB1 CAN wideband kit is what we fit, and it's set up through the Wideband O2 Sensor function instead.
Wiring
The Wiring tab shows how the sensor connects to the ECU. Because the signal is a small voltage that's easily upset by ignition noise, we use a shielded AVI where possible. On the Elite, AVI1 and AVI6 are shielded. When you join the wires, make sure the shield braid can't touch the inner signal conductor. Heated sensors also need their heater wired; see O2 Heater for that side.
Display and diagnostics
| Setting | What it does | Our advice |
|---|---|---|
| Display Maximum | Sets the top of the voltage scale on gauges showing narrowband voltage | Just above the sensor's normal peak so the swing is easy to read |
| Raw Min | Flags DTC P0143 when the voltage drops below this value | Set it below the lowest voltage a healthy sensor produces when lean |
| Raw Max | Flags DTC P0144 when the voltage goes above this value | Set it above the highest voltage a healthy sensor produces when rich |
| DTC Severity | Links each DTC to an Engine Protection level: None, or Level 1, 2 or 3 | None or a mild level. A failed narrowband rarely justifies protecting the engine |
Severity levels only take effect if Engine Protection is enabled. Voltage outside the normal range usually means a wiring fault or a failed sensor, which is worth knowing before closed loop starts making fuel corrections based on bad data.
If the car only needs to pass emissions or hold stoich at cruise, a narrowband is enough. For anything else, tune with a wideband.
