Code P0421: Catalyst Efficiency Below Threshold
NOTE:
For component terminal identification, see TERMINAL IDENTIFICATION
in this article. For wiring diagrams, see WIRING DIAGRAMS in the WIRING DIAGRAMS
section.
No specific self-diagnostic test is provided by manufacturer. Check catalytic converter, engine control module and check for cracked exhaust manifold. Also, refer to the BASIC TESTING - 1.5L and SYSTEM/COMPONENT TESTS - 1.5L articles.