Check engine light on???
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 3,028
Likes: 226
From: Locust Valley NY USA
Check engine light on???
My check engine light came on. the only code i found is
10 pcm p0420 TWC system Low Efficiency Bank 1.
What does that mean??? Car is not running rough or anything unusual.
Fred
10 pcm p0420 TWC system Low Efficiency Bank 1.
What does that mean??? Car is not running rough or anything unusual.
Fred
Race Director
Joined: Sep 2002
Posts: 10,668
Likes: 0
From: You should probably lurk more.
Possible bad catalytic converter?
DTC P0420 Catalyst System Low Efficiency Bank 1
Circuit Description
In order to maintain a reasonably low emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), the engine controls system uses a 3-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and Carbon Dioxide. The catalyst also reduces NOx, converting it to Nitrogen. The PCM monitors this process using Bank 1 HO2S #2. Bank 1 HO2S #2, located in the exhaust stream past the 3-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signal will be far less active than that produced by Bank 1 HO2S #1. This indicates that the 3-way catalytic converters oxygen storage capacity is below a threshold considered acceptable.
The PCM performs this diagnostic at idle when the conditions for running this DTC are met, the following occurs:
The PCM captures the current rear HO2S rich/lean status.
The Air Fuel ratio transitions from rich to lean or lean to rich depending on the capture rear HO2S rich/lean status.
The Air Fuel ratio transitions a second time opposite the first Air Fuel ratio transition.
The PCM captures the response time (the time the HO2S goes from below 300 mV to above 600 mV and from 600 mV to below 300 mV) of the front and rear Heated Oxygen sensors when the Air Fuel ratio transitions occurred.
The PCM measures the time it takes the rear HO2S voltage to cross a reference rich/lean threshold minus the time it takes the front HO2S voltage to cross the same rich/lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of the catalyst. This DTC sets if the time exceeds a predetermined threshold.
Circuit Description
In order to maintain a reasonably low emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), the engine controls system uses a 3-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and Carbon Dioxide. The catalyst also reduces NOx, converting it to Nitrogen. The PCM monitors this process using Bank 1 HO2S #2. Bank 1 HO2S #2, located in the exhaust stream past the 3-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signal will be far less active than that produced by Bank 1 HO2S #1. This indicates that the 3-way catalytic converters oxygen storage capacity is below a threshold considered acceptable.
The PCM performs this diagnostic at idle when the conditions for running this DTC are met, the following occurs:
The PCM captures the current rear HO2S rich/lean status.
The Air Fuel ratio transitions from rich to lean or lean to rich depending on the capture rear HO2S rich/lean status.
The Air Fuel ratio transitions a second time opposite the first Air Fuel ratio transition.
The PCM captures the response time (the time the HO2S goes from below 300 mV to above 600 mV and from 600 mV to below 300 mV) of the front and rear Heated Oxygen sensors when the Air Fuel ratio transitions occurred.
The PCM measures the time it takes the rear HO2S voltage to cross a reference rich/lean threshold minus the time it takes the front HO2S voltage to cross the same rich/lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of the catalyst. This DTC sets if the time exceeds a predetermined threshold.
