CEL P0420
#2
RE: CEL P0420
This trouble code is a couple of things:
An O2 sensor (either one in front of or the one behind the catalytic converter) isn't working properly
Bad coolant temp sensor
Damaged/Bad/Leaking exhaust manifold, catalytic converter, muffler(s)
Some suggested steps for troubleshooting a P0420 code include:
[ul][*]Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.[*]Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).[*]Inspect the downstream heated oxygen sensor (HO2), replace if necessary[*]Replace the catalytic converter [/ul]
If it is heating up, you could have a plugged catalytic converter, but my bet would be a bad coolant temp sensor. That would be the cheapest way to go. (I believe) Good Luck!
An O2 sensor (either one in front of or the one behind the catalytic converter) isn't working properly
Bad coolant temp sensor
Damaged/Bad/Leaking exhaust manifold, catalytic converter, muffler(s)
Some suggested steps for troubleshooting a P0420 code include:
[ul][*]Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.[*]Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).[*]Inspect the downstream heated oxygen sensor (HO2), replace if necessary[*]Replace the catalytic converter [/ul]
If it is heating up, you could have a plugged catalytic converter, but my bet would be a bad coolant temp sensor. That would be the cheapest way to go. (I believe) Good Luck!
#3
RE: CEL P0420
I throw an occational p0420 code. I have a 3" downpipe and Magnaflow high flow cat. ZZPerformance also found a #4 cylinder misfire.
My guess is that you have lots of miles on the car. The code says catalytic convertor inneficiency. Bad cat's don't usually throw a code, but will affect performance SERIOUSLY! Shifting, also. It's not the temp sensor. ?????? Maybe a tune up is in store. I replace the coil for the #4 cylinder, and ordered the other 2 (FACTORY COILS ONLY!) Wires are next, if this doesn't help. I DO know my milage is now better.
My guess is that you have lots of miles on the car. The code says catalytic convertor inneficiency. Bad cat's don't usually throw a code, but will affect performance SERIOUSLY! Shifting, also. It's not the temp sensor. ?????? Maybe a tune up is in store. I replace the coil for the #4 cylinder, and ordered the other 2 (FACTORY COILS ONLY!) Wires are next, if this doesn't help. I DO know my milage is now better.
#4
RE: CEL P0420
P0420 code is the catalityc converter. What year is it? If it's an '01-'02, check this post https://montecarloforum.com/m_12459/tm.htm
That was the problem with mine.
That was the problem with mine.
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