Catalyst System Efficiency Below Threshold (Bank 1)
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
Catalyst System Efficiency Below Threshold (Bank 1)
Ok, this little code has been annoying me for quite some time. About a year ago it would trip the check engine light once every few months. Now it has tripped it 3 times in the last month and its getting annoying. The car has no symptoms and I cannot figure out how to test for what the problem may be...
Here is what causes the code:
A code P0420 may mean that one or more of the following has happened:
-Leaded fuel was used where unleaded was called for
-An oxygen sensor is not reading (functioning) properly
-The engine coolant temperature sensor is not working properly
-Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
-Retarded spark timing
-The oxygen sensors in front and behind the converter are reporting too similar of readings
I have been paying attention to the conditions when the check engine light trips and its at about 150F oil temp and right after or during heavy acceleration. It has happened right after the ASR goes on too. It can also happen under normal driving conditions but for the last few it was under hard acceleration (at least 1 gear drop).
Any Ideas?
Here is what causes the code:
A code P0420 may mean that one or more of the following has happened:
-Leaded fuel was used where unleaded was called for
-An oxygen sensor is not reading (functioning) properly
-The engine coolant temperature sensor is not working properly
-Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
-Retarded spark timing
-The oxygen sensors in front and behind the converter are reporting too similar of readings
I have been paying attention to the conditions when the check engine light trips and its at about 150F oil temp and right after or during heavy acceleration. It has happened right after the ASR goes on too. It can also happen under normal driving conditions but for the last few it was under hard acceleration (at least 1 gear drop).
Any Ideas?
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,008
From: Texas
Either the aft o2 sensor on bank 1 is bad or the cat is going bad. Swap the rear o2 sensors side to side and see if the code follows. If it does, you know it's the sensor. If it doesn't, you know it's the cat.
Thread Starter
Safety Car
Joined: Dec 2008
Posts: 3,588
Likes: 10
From: North New Jersey
