P0172 Diagnostic for 2009 Chevrolet Impala: O2 Sensor Replacement Not Clearing Check Engine Light
I'm experiencing a persistent check engine light on my 2009 Chevrolet Impala despite replacing both oxygen (O2) sensors. After installing the first sensor, the code cleared and the light turned off temporarily. However, after replacing the second O2 sensor, the check engine light remains on. The fault code P0172 is still present. My question: if the code does not clear after reinstallation of the second sensor, how long should I wait before assuming there's another underlying issue? Is it possible that the problem lies elsewhere, such as in fuel pressure or vacuum leaks?
Check for vacuum leaks. Inspect all hoses and connections around the intake manifold. Also verify fuel pressure and perform a leak-down test to rule out engine-related issues that may be contributing to the P0172 code.