Join Date: Nov 2016
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FWIW, the AFM on GM engines uses oil to engage the lifters which then prevent the intake and exhaust valves from opening, so the cylinder compresses spent exhaust gas over and over again, kind of like a gas spring.
Which stands to reason, if there is an oil pressure sensor fault, the AFM would become disabled. I have heard and read that the wrong viscosity oil can cause this very issue.
If that isn't the issue, I know a few years ago two members here had his AFM stop working all of a sudden, then shortly after started throwing the P0523 code. Took it to a dealer, they swapped out the oil pressure sensor and everything started working again.
Hope this helps!
08 Impala LTZ
Blackvue DR-470 2-Ch w/ PMP & GPS
Ultragauge MX 1.3
Dynomax 3" tips
Chevrolet Performance STBs + DR custom brackets
30% Llumar tint
Techno Steel interior trim / leather shifter
Reverse light / full interior / instrument cluster LED retrofit
LED headlights / fog lights
Stant locking gas cap
WeatherTech front liners / window deflectors
GM molded splash guards
Firestone Firehawk Wide Oval UHP