What is triggering my p0420 code?

What is your question?

Hello, I have a 2003 Toyota Camry that is throwing a p0420 code. However, it doesn't always do this. Interestingly, it only does it when I've been using the air conditioner. If I don't use it for a while, my check engine light goes off and doesn't turn back on until I use the AC again. Any thoughts about what is going on? I'm having trouble making the connection between the AC and the catalytic converter. Thanks

How long has your 2003 Toyota Camry had this problem?

A couple of years

Visitor

in Charlottesville VA

Jun 22, 2019

2 Replies

Popular Answer

DaveJMon Jun 22, 2019

There is no correlation at all. Have testing performed to monitor the oxygen sensor before and after the catalytic converter. If you find the exhaust gas measurement does not change, then the catalyst is not functioning and must be replaced. P0420 codes are typically never erroneous or related to any other theoretical failure.

pushrodon Jun 22, 2019

I don’t think emissions testing is required in that area - Virginia’s annual ‘safety inspection’ procedure doesn’t include nor is it concerned with the check engine light.. There is a trick or two that can be helpful with this code - especially for a 2003 year model vehicle. Just saying..

pushrodon Jun 22, 2019

Air conditioner is adding a continuous load on the engine which can alter idle speed as well as various operating system conditions - that may be the relationship between the a/c being engaged and the light turning on as this would certainly have an effect on exhaust gases .. Will be more pronounced if another operating system problem exists. There is a slim possibility the downstream 02 sensor is causing this problem - however if scan tool readings reveal upstream and downstream sensors are switching simultaneously and showing the same values with engine on - catalyst HAS been depleted.. Some code readers have the capability of live sensor data readings. Good luck!

Reply in Thread

Join the conversation!

What are the best Toyota repair shops?

RepairPal Certified shops can diagnose and repair your 2003 Toyota Camry. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.