I've been having the P0420 code for a while and it would go away randomly. Combine with the cluster not able to report all the lights correctly, it does make it hard to notice when I get any error lights. What I noticed now is that the OBD2 scanner still read the code and when I turn the car to on position, the SES light would turn on, so its not that the light completely die, but it won't stay on even when there is a code. Any solution or from what I read, I'll have to resolder the board?

 

It might be completely normal though, the SES light only turns on when the 2-trip requirements are met. A single trip will store the code but not turn on the SES light.

 

2 trip requirement? can you explain what it is? I never heard of it. It has been a week since I found out there is a code and the light still won't light up.

 

Basically it had to trigger the same fault TWICE for it to illuminate the SES for most codes, if it only pings a single fault it stores it as a hidden code.

You need to keep in mind how much data is going through the computer, sets of data for each sensor many times per second, there are occasionally going to be discrepancies as the machine wears but it it has 1 fault value out of 100,000 values over the course of an hour or so of data per sensor that's not going to be a good reason for the customer to take their car to the service department. Thus the 2trip requirement for the light to actually turn on since the recommended course of action when the light turns on is to stop the vehicle and/or drive immediately to the service department.

 

Ahh, never knew they would hide the code like that. Only found this out since the cluster is messed up.