1998 Nissan Maxima P0325 and P0407 Code Diagnosis: Linked Issues or Separate Faults?
I recently purchased a 1998 Nissan Maxima that previously passed smog inspection. However, 33 days after purchase, the Service Engine Light (SEL) illuminated, triggering diagnostic codes P0325 and P0406. I have two main questions: 1) Could these two fault codes be related to a single underlying issue? For example, could an EGR system problem cause both a knock sensor malfunction (P0325) and an emissions-related code (P0406)? 2) Would a mechanic have been able to detect this issue during the pre-inspection without the SEL lighting up? I've also learned more about P0325 through community input, which has helped clarify its significance in engine performance and knock detection.
Please confirm the engine type — this post was initially tagged to a Sentra thread but is now relevant to a 1998 Maxima. This is a new topic, not a cross-post. Welcome to emissions diagnostics — there's often financial incentive in identifying these issues. My two cents: 1) Yes, it's plausible that the P0406 (EGR system issue) could cause engine knocking, which might trigger the P0325 knock sensor code. 2) If no check engine light activated for three months prior to now, the problem likely didn't exist until recently. Were there any modifications or maintenance actions performed on the vehicle before the SEL came on?