Had my manifold replaced, basically P0420 came up with very poor/no response from throttle at stop to go. Today I found a loose nut at the stud connecting the exhaust pipe to the manifold. Seemed to be an easy fix, just tighten a nut? Did a test run nailed the gas from a dead start now able to lay rubber. Question is do I have reset the CEL to clear the code or will it reset itself? Would rather not reset as it has to pass smog test and it seems to take for ever to complete the monitor tests. Thanks Greg
Code P0420
- Thread starter pell
- Start date
The "Manifold Leak" is right at the bottom a long list of causes for setting the P0420 Code. The Article linked below is a very comprehensive breakdown of the symptoms, causes and things to focus on during Diagnostics.
Having dealt with the Loose Exhaust Pipe Fastener, the only way to find out if the CEL will stay off is to clear it with capable Scanner and then thrash out the situation afterwards if it resets, well in advance of the Smog Test in order to have time to investigate, repair the issue and ensure that the CEL stays Off:
www.700r4transmissionhq.com
Having dealt with the Loose Exhaust Pipe Fastener, the only way to find out if the CEL will stay off is to clear it with capable Scanner and then thrash out the situation afterwards if it resets, well in advance of the Smog Test in order to have time to investigate, repair the issue and ensure that the CEL stays Off:
P0420 Chevy Trailblazer OBDII Code Definition and Diagnosis | Drivetrain Resource
This page is meant to help you troubleshoot the Chevy Trailblazer P0420 trouble code. It covers the P0420 code's meaning, symptoms, causes, and possible solutions. P0420 is the most common OBDII code and is virtually never a breakdown risk. A failing oxygen sensor or bad catalytic converter are...
www.700r4transmissionhq.com
Mooseman
Moderator
Yes, clear the codes and see if it comes back. May take a day or two to have the I/M readiness indicators set for the smog test. Just drive it normally and they should eventually set. Most jurisdictions allow one of them to not be set during the smog check as the EVAP usually takes a while set. Most scanners are able to tell you the status of the I/M readiness.
So after not getting P0420 code to clear, I decided to change the down stream sensor. Much to my surprise the "mechanics" that replaced the manifold actually cut a section of cat pipe, welded in but didn't weld the top. (looks like they tried to patch with JB weld or something else). When I saw this I left the sensor in. So basically I used a piece of aluminum with boiler gasket and two large hose clamps to seal the cut on the top. No more codes! I did clean the throttle body and the fuel injectors trying to correct the code and this truck runs great. It moves by itself when you take your foot off the brake which I never had that happen before. Thanks for the help everyone
