OBDII code 420. I replaced the O2 sensors. Before I did that I had code 133( slow response from O2 sensor #1.\015 Answers : Hi Steve, The ignition timing is computer controlled and is not manually adjustable. The ignition timing is in part controlled by the knock sensor and any problem there will have effect on the timing. Regards John The ignition timing would not be adjustable. Code 420 is for a weak catalytic converter, which can be caused by a defective cat, or a fuel problem, or the O2 sensors. The only time ignition timing is a possible cause is when you have a distributor or something has happened to the ignition module and the timing is delayed. Repair Help & Product Troubleshooting for 2004 Toyota Corolla Repair Help & Product Troubleshooting for 2004 Toyota Corolla Tips for a great answer: - Provide details, support with references or personal experience . - If you need clarification, ask it in the comment box . - It's 100% free, no registration required.
