I have a 2002 Neon that I am teaching my teenagers to drive on but also love it as a commuter car with excellent economy. She is a base model with a manual and no AC.

She is advising P1684 and P0420 codes.

I understand that the P1684 is because I very recently disconnected the battery.

Regarding the P0420 code, it seems most likely cause is the upstream O2 sensor, but could be a bad cat or a vacuum leak. According to this website http://ricksfreeautorepairadvice.com...ix-code-p0420/ I should buy a new scan tool that shows live data.

Should I just recheck for vacuum leaks and replace the upstream O2 sensor or buy a new scanner that shows live data and fix it next month when I have the funds?

Thank you in advance for your attention.

Best regards,
Scott

 

Personally I'd start with replacing the O2 sensor.