I have a 2002 Nissan Altima that is showing the following codes. What does this mean
P0420, P0217 and P1217. Thanks.

- P1217 Engine Over Temperature (Overheat) / Engine Coolant Temperature
- P0420 Catalyst System Efficiency Below Threshold (Bank 1) - Basically this means that the oxygen sensor downstream (after) the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
- P0217 Engine Coolant High Temperature Enrichment Protection

Looks like you need to change your o2 sensor!

The 1217 and 0217 codes do not require diagnosing as long as you fixed the overheating problem. All nissan's throw this code when overheated. The 0420 code is only caused by two things. Either there is a recall for reflashing your ecm or your cat converter is bad.