Exhaust Gas Oxygen Sensors (Optional)

What the sensor does

An exhaust gas oxygen sensor samples the exhaust stream and tells the ECU whether the engine is running rich or lean. It's optional on an Elite install, but it's needed for closed loop fuel control and it makes logging far more useful.

Where to mount it

Put the sensor close to the engine, in the exhaust just after the header or extractor collector where all the cylinders' gas has mixed together. That gives a reading that represents the whole engine, and it keeps the sensor hot enough to work properly.

• Using a factory bung: many late-model engines already have one, and the sensor should thread into a standard exhaust mount. Some factory systems put the bung as much as about 2 feet (around half a meter) down the pipe from the headers, which is fine.
• No existing bung: you'll need to have one welded into the exhaust. We like to mount it with the sensor tip pointing down at an angle, above horizontal, so condensation can't pool on the element.
• On a turbo engine: mount it after the turbo, in the downpipe.

Routing the wiring

Keep the sensor harness well away from the exhaust. The pipe gets hot enough to melt insulation, and a shorted sensor wire is a frustrating fault to chase. Secure the lead so it can't sag onto the pipe or get caught by moving suspension or driveline parts.

Which input to use

A narrowband sensor produces a small signal, roughly 0 to 1V, and it can't drive much of a load. The Elite's AVI 1 and AVI 6 are designed to place as little load as possible on that kind of signal, so those are the inputs to use for a narrowband sensor wired straight to the ECU.

A wideband sensor is a different story. It needs a controller between the sensor and the ECU, like the WB1 CAN wideband controller, which sends lambda over CAN instead. See our WB1 and WB2 controller article.

Next steps

Once it's installed, set up the sensor in ESP using our narrowband O2 sensors article, and read up on O2 control if you want closed loop fueling. The other input guides in this series cover sensors like the knock sensor.