Engine runs fine after ECU reset, poorly shorty after

[Bluevitz-rs]

Originally Posted by tmontague

The pre cat O2 sensor is an AFR sensor (wideband), the post cat is a typical short band O2 sensor.

I believe Blue vits is referring to the primary AFR sensor, but you may as well check both.

The primary is NOT an AFR on an Echo. It is an O2 sensor.



And yes the post Cat O2 Sensor will influence the long term fuel trim.

The primary is before that Cat. It is connected in the engine bay. The connector is mounted to the rear engine mount and is a PITA to disconnect. The secondary O2 is the one connected under the shifter.