Code P0420

[hasteyoman]

my po420 code is on, on my 2006 buick lucerne. even if i clear it it comes within 2-4 days. really getting irritated. changed the catalytic converter and a 02 sensor .. please help

 

[MelsRegal]

Here are a number of other causes

P0420 Catalyst System Efficiency Below Threshold

How to diagnose, repair, and info on symptoms and causes of a P0420 engine code which means the catalytic converter is no longer performing at a normal level.

www.obd-codes.com

 

[2007LucerneCXL]

On the code if a shop or if you are doing the repairs. There's two O2 sensors and it's possible, depending on sequence of repairs that the harness / O2 sensor may have been damaged or it's a poor quality aftermarket O2 sensors. A O2 sensor extender may resolve the problem, the type of catalytic converter may also be the cause. How many miles and what type of driving, highway or city, since installing?

Another site that may help.

Part 1 -How to Test Trouble Code P0420 (GM 3.8L)

Page 1 of 4: P0420 Catalyst Efficiency Below Threshold (Bank 1). How to Test Trouble Code P0420 (GM 3.8L). Symptoms of a P0420. What Causes the Catalytic Converter to Fail. Excessively Rich condition

troubleshootmyvehicle.com