Engine runs fine after ECU reset, poorly shorty after

[Zachccccc]

Originally Posted by Bluevitz-rs

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.

So to test the Primary do the voltmeter pin check and it should oscillate from .4-.9v ?
I'm still not certain which pin to test the white one on the OBD ?

How would one go about replacing that sensor if it is bad, any tips/tricks ?

Also, are there tests that can be done to diagnose a bad MAF?

Originally Posted by Bluevitz-rs

Actually the misfire is probably what caused the 420 code.
It's actually crazy how far out the readings on the sensors can be screwing with other components and not set a code.

Oh, ok gotcha !