How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Travis Your Own Question
Travis, Technician
Category: Car
Satisfied Customers: 980
Experience:  7+ years of GM dealership experience, GM ASEP trained, Assoc. Degree in Auto. Tech.
Type Your Car Question Here...
Travis is online now
A new question is answered every 9 seconds

i have a 2004 saturn ion that kicked a P0420 code what does

Customer Question

i have a 2004 saturn ion that kicked a P0420 code what does that mean
Submitted: 7 years ago.
Category: Car
Expert:  Travis replied 7 years ago.

Thanks for the question.


A three-way catalytic converter (TWC) controls exhaust emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The catalyst within the converter promotes a chemical reaction which oxidizes the HC and the CO that is present in the exhaust gas. This process will convert the HC and the CO into water vapor and carbon dioxide (CO2), and will reduce the NOx, converting the NOx into nitrogen. The catalytic converter also stores oxygen. The engine control module (ECM) monitors this process by using a heated oxygen sensor (HO2S) which is in the exhaust stream past the TWC. The HO2S produces an output signal which indicates the oxygen storage capacity of the catalyst. This in turn indicates the catalysts ability to convert the exhaust emissions effectively. The ECM monitors the catalyst efficiency by first allowing the catalyst to heat, then waiting for a stabilization period while the engine is idling. Then, the ECM adds and removes fuel while monitoring the reaction of the HO2S. When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the HO2S 1. When the HO2S 2 response is close to that of the HO2S 1, the oxygen storage capability or efficiency of the catalyst may be degraded below an acceptable threshold. If the ECM detects the degraded condition DTC P0420 sets.


Basically, the catalyic converter has failed and needs to be replaced.


If you have any questions, please let me know.




Related Car Questions