2000 Nissan Maxima Trouble Code P0420 Catalyst System Efficiency Below Threshold

My 2000 Nissan Maxima just failed the emissions test due to a bad gas cap and for the check engine light being ON. The DTC reported are P0420 Catalyst System Efficiency Below Threshold Bank 1. This car fails every time it has to get a smog check. The car is running fine and we don't have the extra funds to pay right now. How can we get it through emissions and not have to do much more than buying the gas cap? Thanks.

Answer:

Trouble Code P0420 indicates a problem with your Nissan Maxima's three-way catalytic converter or not as efficiently as the ECU is expecting. The problem can be due to the CAT not functioning properly or a defect with the rear oxygen sensor which is used to report the condition of the exhaust exiting the CAT. If the O2 sensor itself is defective the ECU may interpret the sensors results as a defective catalytic converter. It is best to ensure both rear oxygen sensor and catalytic converter are working properly.

Regarding trouble code P0420... Nissan has put out a service bulletin (see link below). As far as assistance with repairing your Nissan's smog check problem we recommend looking into the CAP Consumer Assistance repair program.

2000 Nissan Maxima TSB

California Consumer Assistance Program

posted by SmogTips Support