Q: The following codes showed up: PO420-catalyst system efficiency below threshold (bank 1) and PO430-catalyst system efficiency below threshold (bank 2). I don't know much about cars. What does that mean? It has caused my sevice engine light appear
A: Nice you have a code reader. Anyway....it means both oxygen sensors are detecting somthing they shouldn't. It doesn't necesarrily mean they need to be replace. I would get a tune up done and go from there. Before you take in for a tune up reset the ecu. A lot mechs will disagree with me here, but my reasoning is to keep from being told you replace a bunch of things you don't need replace. A bad pvc valve would cause the O2 sensors to have a bad reading (catch my drift). Start with tune up especially if you haven't had one done in a while.