Question about 1996 Chevrolet Blazer

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My check engine light came the code is p0420 - 1996 Chevrolet Blazer

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Technical Description

Catalyst System Efficiency Below Threshold (Bank 1)
What does that mean?

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms

You will likely not notice any drivability problems, although there may be symptoms.
Causes

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

Possible Solutions

Some suggested steps for troubleshooting a P0420 error code include:

* 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

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

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Posted on Sep 07, 2010

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Catalyst system efficiency below threshold bank one. That is a code that sets when your catalytic convertor for cylinders 1,3 & 5 is plugged. But if you have only one convertor it is a sign that you may have a fuel pressure regulator or fuel injector leak under the intake plenum. Check your fuel pressure. It should hold constant. If it slowly drops you will need to pull upper intake (plenum) & see which is leaking.

Posted on Sep 07, 2010

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Po420 >Catalyst System Efficiency Below Threshold (Bank 1)
If that is the only code and you have no drivibility problems then replacement of the Bank 1 converter is your only option.
Bank 1 is the side of the engine inwhich cylinder number1 is located.
Be advised the computer uses Bank1 upstream and downstream oxygen sensors to check the catalytic converter

Posted on Sep 07, 2010

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SOURCE: 2003 toyota camry

P0420 is a cat code. Sometimes, you can replace the upstream & downstream air/fuel & O2 sensors, run some good fuel injection cleaner thru it, and that might fix the problem. If not, you may need to replace the cat. Note that the cat is covered under warranty for 8 yrs/80,000 miles. Toyota will replace it if it has gone bad, for free.

Posted on Sep 16, 2008

  • 1201 Answers

SOURCE: need info on codes PCM.P0134 and P0420

Both codes are for the oxygen sensors.
P0134 oxygen sensor on bank #1, sensor #1 is bad.
P0420 oxygen sensor on bank #1, the sensor down by the catalytic converter, is also bad.

Posted on Mar 26, 2009

  • 1 Answer

SOURCE: Check Engine Light came on with code p0420. Dealer wants $3900 to fix "b2 manifold and front pipes. Does this make sense. Are their better alternatives. I left the dealership without fixing it and the

if u r have lexus or v 6 or v8 so change or check u r leak of exhouse bank #1 driver side if u all want any question send me mail malikume@eim.ae

Posted on Jul 25, 2009

  • 495 Answers

SOURCE: 2003 nissan murano with check engine light codes

P0420 is Catalyst System Efficiency Below Threshold - Bank 1
and
P0456 is EVAP Control System Very Small Leak (Negative Pressure Check)

Posted on Nov 22, 2009

bschilz
  • 2049 Answers

SOURCE: check engine light-on OBD code's P0420 &

The codes are Catalyst System Efficiency Below Threshold (Bank 1)&(Bank 2).

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

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
Some suggested steps for troubleshooting a P0420 code include:
  • 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
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem.

Posted on Oct 06, 2009

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TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
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Code P0420


P0420 Catalyst System Efficiency Below Threshold (Bank 1)

There is one 02 sensor in front of the catalytic converter (called upstream), and one behind it (downstream). When the engine is warmed up and running normally the upstream oxygen sensor reading fluctuates and the downstream one is fairly steady. In the case where both readings are fairly steady, a P0420 check engine light code is set.

Possible Causes:
Oxygen (O2) sensor not working correctly
Damaged or leaking exhuast (pipe, manifold, catalytic converter)
Damaged catalytic converter

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