Postby VStar650CL » Mon Sep 25, 2023 9:20 pm
That's a very unusual code, it's the opposite of a vacuum leak. The ECM is trying to lean bank1, not rich it. Normally that's an issue with one or more of the injectors, but normally that also means some sort of miss or rough running. Fuel pressure or MAF problems would be affecting both banks. Since you're not getting any of that, my first guess would be that your bank1 A/F Sensor (front O2) is lying to the ECM.