I have this problem a Pontiac Vibe 2003 (toyota corolla/matrix platform) where if I do anything to adjust the A/F Ratio it just balances back to 14/1

So for I tried Eagle Research EFIE & a Camcom. But according to A/F ratio gauge(narrowband) it will learn out for a few seconds then eventually go back to the default mix.

Next step is to fool the rear O2 sensor because I believe somehow when learn burn exhaust hits the 2nd sensor the ECU knows to enrich the gas mix again or gives a P0420 check engine light.

I will do different runs this week with a EFIE on the rear O2 sensor & camcon controlling the front to try to achieve a lean mix.

I hope anyone else struggling with ECU problem this can offer ideas for me to try.

Front sensor measures A/F ratio. Rear sensor measures catalyst efficiency.

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