help p0420 code
help p0420 code I got this code. I went to and got my emission tested with the service engine soon light on. The car passed the emission test so would it be the cat or the o2 sensor? I figure the if it was the cat it would fail the test. I apperciate any help.
Tim
Tim
DTC P0420 or P0430
In order to maintain 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 oxidizestheHC and CO in the exhaust gas. This reaction converts these chemicalsinto harmless water vapor andcarbondioxide. The catalyst alsoreduces NOx, converting the NOx tonitrogen. The powertrain control module (PCM)monitorsthisprocess using Bank 1 HO2S #2. Bank 1HO2S #2, located inthe exhauststream past the 3-way catalytic converter, produces anoutput signal which indicatestheoxygen storage capacity of the catalyst.This determinesthe catalyst's ability to effectively convert theexhaust emissions. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signalwill be far less active than the signal produced by Bank 1HO2S #1. This indicates that the 3-way catalyticconvertersoxygen storage capacity is below an acceptable threshold.
When the Conditions for Running this DTC are met, the following conditions occur:
• The PCM captures the current rear HO2S rich-to-lean status.
• The Air/Fuel ratio transitions from rich to lean, or from lean to rich, depending on the capture rear HO2S rich-to-lean status.
• The Air/Fuel ratio transitions a second time opposite the first Air/Fuel ratio transition.
• The PCM captures the response time of the front and rear heated oxygen sensors when the Air/Fuelratio transitions occurred. The response time is the time during which the HO2S goes from below 300 mV to above 600 mV, and from 600 mV to below 300 mV.
• The PCM measures the time for the rear HO2S voltage to cross a reference rich-to-lean threshold, minus the time for the front HO2S voltage to cross the same rich-to-lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of thecatalyst. This DTC setsif the time exceeds a predetermined threshold.
Conditions for Running the DTC
• DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0332, P0335, P0336, P0341, P0342, P0343, P0351-P0358, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449 , P0500,P0502, P0506, P0507, P0704, P0801, P0803, P1258, P1336, P1415, P1416, and P1441 are not set.
• The engine is operating for more than 450 seconds.
• The ECT is between 75°C (167°F)-120°C (248°F).
• The IAT is between -18°C (64°F)-80°C (176°F).
• Since the end of the last idle test, the engine speed is more than 1,000 RPM for a minimum of 37 seconds for a manual transmission
• Since the end of the last idle test, the engine speed is more than 1,000 RPM for a minimum of 44 seconds for an automatic transmission
• The BARO is more than 74 kPa.
• The fuel system is operating in closed loop.
Conditions for Setting the DTC
The PCM determines that the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.
In order to maintain 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 oxidizestheHC and CO in the exhaust gas. This reaction converts these chemicalsinto harmless water vapor andcarbondioxide. The catalyst alsoreduces NOx, converting the NOx tonitrogen. The powertrain control module (PCM)monitorsthisprocess using Bank 1 HO2S #2. Bank 1HO2S #2, located inthe exhauststream past the 3-way catalytic converter, produces anoutput signal which indicatestheoxygen storage capacity of the catalyst.This determinesthe catalyst's ability to effectively convert theexhaust emissions. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signalwill be far less active than the signal produced by Bank 1HO2S #1. This indicates that the 3-way catalyticconvertersoxygen storage capacity is below an acceptable threshold.
When the Conditions for Running this DTC are met, the following conditions occur:
• The PCM captures the current rear HO2S rich-to-lean status.
• The Air/Fuel ratio transitions from rich to lean, or from lean to rich, depending on the capture rear HO2S rich-to-lean status.
• The Air/Fuel ratio transitions a second time opposite the first Air/Fuel ratio transition.
• The PCM captures the response time of the front and rear heated oxygen sensors when the Air/Fuelratio transitions occurred. The response time is the time during which the HO2S goes from below 300 mV to above 600 mV, and from 600 mV to below 300 mV.
• The PCM measures the time for the rear HO2S voltage to cross a reference rich-to-lean threshold, minus the time for the front HO2S voltage to cross the same rich-to-lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of thecatalyst. This DTC setsif the time exceeds a predetermined threshold.
Conditions for Running the DTC
• DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0332, P0335, P0336, P0341, P0342, P0343, P0351-P0358, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449 , P0500,P0502, P0506, P0507, P0704, P0801, P0803, P1258, P1336, P1415, P1416, and P1441 are not set.
• The engine is operating for more than 450 seconds.
• The ECT is between 75°C (167°F)-120°C (248°F).
• The IAT is between -18°C (64°F)-80°C (176°F).
• Since the end of the last idle test, the engine speed is more than 1,000 RPM for a minimum of 37 seconds for a manual transmission
• Since the end of the last idle test, the engine speed is more than 1,000 RPM for a minimum of 44 seconds for an automatic transmission
• The BARO is more than 74 kPa.
• The fuel system is operating in closed loop.
Conditions for Setting the DTC
The PCM determines that the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.
Launching!
Joined: Feb 2004
Posts: 254
Likes: 0
From: Waterford, MI
Twort
It all has to do with how GM calibrated to the standard that CARB set.
Auto companies are allowed a set standard by CARB before they have to turn the light on. However GM calibrated to less than the standard. The diagnostic is running exactly as it should (i.e. you get the light when it's out of range) but you can think of it as your window is just smaller than it needs to be. The result: you set the light but still pass emissions because you are still within the CARB / EPA range.
It all has to do with how GM calibrated to the standard that CARB set.
Auto companies are allowed a set standard by CARB before they have to turn the light on. However GM calibrated to less than the standard. The diagnostic is running exactly as it should (i.e. you get the light when it's out of range) but you can think of it as your window is just smaller than it needs to be. The result: you set the light but still pass emissions because you are still within the CARB / EPA range.
Last edited by ICEBOX; Apr 11, 2005 at 07:17 AM.
