Question

2002 Opel Vectra C Z18XE, P0420-5A Catalyst System Efficiency Below Threshold (Bank 1) What is this error?

Answer 1

Hi there,

This error generally means the catalytic converter is no longer doing the job. It can also be the result of a faulty rear O2 sensor or an exhaust leak. This is the bank 1 catalytic converter. Most cases you will need to replace the converter to resolve the problem.