2000 Volvo S70 Check Engine Light On: Fault Codes P1672 and P1670 Explained

My 2000 Volvo S70 has recently started having difficulty starting. It will sometimes start on the first attempt, but other times it will repeatedly crank and then immediately shut off—this cycle repeats for several minutes before the engine finally starts. I ran a diagnostic and found two check engine light-related fault codes: P1672 and P1670, in addition to an oxygen sensor issue. While I understand what an O2 sensor problem is, I'm unsure about these specific codes. Can anyone explain what P1672 and P1670 mean in the context of a 2000 Volvo S70? Any insights or troubleshooting steps would be greatly appreciated. Thanks for your help!