check engine light question
Dec 11, 2006, 08:00 AM
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check engine light question
i just checked my cel at my local autozone and came up with this...
P0421...catalist temp bellow treshold Bank 1!!!
Does anyone has an idea on what this is?
P0421...catalist temp bellow treshold Bank 1!!!
Does anyone has an idea on what this is?
Dec 11, 2006, 08:04 AM
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P0420, P0421 Codes - “Without Guidance, We are Lost”
As a byproduct of laboratory research, we often see the same problem in several different vehicles. Looking at these three catalyst efficiency codes, we see the same codes occur on three clean vehicles. If the OBD II system really works, why do these vehicles indicate an emission problem?
In some of our other laboratory vehicles, the MIL illumination was caused by conditions not seen during the Federal Test Procedure (FTP) emission test. Could this be the case for these vehicles? Let’s look at these vehicles and see.
Background
These vehicles all came into our lab with lit Malfunction Indicator lamps (MILs). As part of our OBD II research, we tried to identify vehicles that had the potential to fail an emission test, so by and large the cars entering our study had an illuminated MIL. These vehicles did not generally have drivability problems, and showed no obvious underhood defects.
After scanning these vehicles, we determined they all had catalyst efficiency codes, either a P0420 or P0421. After scanning, we performed a Federal Test Procedure (FTP), in order to determine tailpipe emissions of each vehicle. In each case, the vehicles came out of the test with clean exhaust (see chart 1). OBD II systems are designed to illuminate the MIL only in cases where exhaust emissions exceed 1.5 times the standard the vehicle was built to meet (for tier 1 vehicles). If the catalyst efficiency of these vehicles were truly low , we would expect the emissions to be high, particularly for hydrocarbons, the pollutant OBD II catalyst monitors are designed to evaluate.
Where to Turn?
At this point, short of evaluating the software of the vehicles computer, we had three choices:
1) Use shop grade equipment to evaluate the catalyst efficiency.
2) Check for Technical Service Bulletins (TSBs).
3) Replace the catalyst based on the OBD II code.
Each choice has its own pros and cons. While there are shop grade tests that will provide a catalyst efficiency number (in percent), the accuracy of these tests
©Colorado State University-NCVECS OBD II Case Study 7
cannot approach the accuracy of the FTP. In other words, using a shop grade
test will not tell us anything we don’t already know based on the FTP. The FTP has said the catalyst performance looked good, so condemning this catalyst with a less accurate test would be an exercise in futility.
Checking for TSBs also has pros than cons. When there is a TSB, we know engineers with data and access to OBD II software have studied at the problem and developed a repair. The TSB must pass review from the EPA, typically within the warranty coverage period. The only real downside to a TSBs occurs when you can’t find one. In that case, your choices are replacing the catalyst or turning off the MIL. We have found that if you clear the codes and extinguish the MIL on an OBD II equipped vehicle, it will sooner or later come back.
The final choice, replacing the catalyst, should only be performed if the car exceeds the emission warranty of OBD II equipped cars- 8 years or 80,000 miles. In fact, replacing a factory catalyst with an aftermarket cat before the emissions warranty expires is a violation of federal statute. Therefore, this option should only be used when a vehicle is outside of the 8 and 80 warranty, at which point the odds are pretty good the catalyst efficiency is low.
Read that, its Helps to Search in the Future.
As a byproduct of laboratory research, we often see the same problem in several different vehicles. Looking at these three catalyst efficiency codes, we see the same codes occur on three clean vehicles. If the OBD II system really works, why do these vehicles indicate an emission problem?
In some of our other laboratory vehicles, the MIL illumination was caused by conditions not seen during the Federal Test Procedure (FTP) emission test. Could this be the case for these vehicles? Let’s look at these vehicles and see.
Background
These vehicles all came into our lab with lit Malfunction Indicator lamps (MILs). As part of our OBD II research, we tried to identify vehicles that had the potential to fail an emission test, so by and large the cars entering our study had an illuminated MIL. These vehicles did not generally have drivability problems, and showed no obvious underhood defects.
After scanning these vehicles, we determined they all had catalyst efficiency codes, either a P0420 or P0421. After scanning, we performed a Federal Test Procedure (FTP), in order to determine tailpipe emissions of each vehicle. In each case, the vehicles came out of the test with clean exhaust (see chart 1). OBD II systems are designed to illuminate the MIL only in cases where exhaust emissions exceed 1.5 times the standard the vehicle was built to meet (for tier 1 vehicles). If the catalyst efficiency of these vehicles were truly low , we would expect the emissions to be high, particularly for hydrocarbons, the pollutant OBD II catalyst monitors are designed to evaluate.
Where to Turn?
At this point, short of evaluating the software of the vehicles computer, we had three choices:
1) Use shop grade equipment to evaluate the catalyst efficiency.
2) Check for Technical Service Bulletins (TSBs).
3) Replace the catalyst based on the OBD II code.
Each choice has its own pros and cons. While there are shop grade tests that will provide a catalyst efficiency number (in percent), the accuracy of these tests
©Colorado State University-NCVECS OBD II Case Study 7
cannot approach the accuracy of the FTP. In other words, using a shop grade
test will not tell us anything we don’t already know based on the FTP. The FTP has said the catalyst performance looked good, so condemning this catalyst with a less accurate test would be an exercise in futility.
Checking for TSBs also has pros than cons. When there is a TSB, we know engineers with data and access to OBD II software have studied at the problem and developed a repair. The TSB must pass review from the EPA, typically within the warranty coverage period. The only real downside to a TSBs occurs when you can’t find one. In that case, your choices are replacing the catalyst or turning off the MIL. We have found that if you clear the codes and extinguish the MIL on an OBD II equipped vehicle, it will sooner or later come back.
The final choice, replacing the catalyst, should only be performed if the car exceeds the emission warranty of OBD II equipped cars- 8 years or 80,000 miles. In fact, replacing a factory catalyst with an aftermarket cat before the emissions warranty expires is a violation of federal statute. Therefore, this option should only be used when a vehicle is outside of the 8 and 80 warranty, at which point the odds are pretty good the catalyst efficiency is low.
Read that, its Helps to Search in the Future.
Last edited by Spooldyou; Dec 11, 2006 at 08:06 AM.
Dec 12, 2006, 09:51 AM
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Another one of these threads?
Guys I think there's like a few of these in the Lancer portion of the site already.
https://www.evolutionm.net/forums/sh...d.php?t=239150
https://www.evolutionm.net/forums/sh...d.php?t=214514
Guys I think there's like a few of these in the Lancer portion of the site already.
https://www.evolutionm.net/forums/sh...d.php?t=239150
https://www.evolutionm.net/forums/sh...d.php?t=214514
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