Question about 1997 Jeep Grand Cherokee

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My abs light won't go off and diagnostics results show issues with catalyst monitoring and oxygen sensor monitoring. What does this mean and how to cure it?

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The abs light has nothing to do with the cat or the o2 sensors but the check engine light would, the cat problem may be a bad cat, these jeeps are famous for cats, if you replace the cat i would also replace the 02 sensors. the abs problem on these is related to a bad speed sensor, theres one in the rear diif and the other in the trany housing.

Posted on Oct 04, 2010

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What is code P0420, check engine light, 2004 Iszuzu Rodeo


Catalyst System Efficiency Below Threshold I have put together the following information about the P0420 fault code. I have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code
  • OBD II P0420
Fault Code Definition
  • Catalyst System Efficiency Below Threshold
Symptoms
  • Check Engine Light will illuminate
  • In most cases, there are no adverse conditions noticed by the driver
  • In some cases, there may be some performance problems noticed by the driver such as a lack of power from a restricted and/or damaged Catalytic Converter
Common Problems That Trigger the P0420 Code
  • Inefficient Catalytic Converter(s)
  • Defective Front or Rear Oxygen Sensor(s)
  • Misfiring engines
Common Misdiagnoses
  • Oxygen Sensors
Polluting Gases Expelled
  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog
  • Most of the aftermarket Converter companies are re-working their designs so they can be certified for use in OBD-II vehicles in California
The Basics
The Catalytic Converter looks like a muffler. It is typically a stainless steel housing over a ceramic honeycomb core. The catalyst itself is made of platinum, palladium, or rhodium, all rare metals, which is why Catalytic Converters are so expensive. These elements reduce the toxicity of harmful exhaust gases that are expelled from the tail pipe. Catalytic converters are quite efficient, but if engine maintenance is neglected or an engine is allowed to "run rough," damage could occur, resulting in costly repairs. To replace the Catalytic Converter, the vehicle is raised to gain access to its underside. The converter is removed from the exhaust system and the new Catalytic Converter is installed.
Want to Learn More?
The Catalytic Converter is a sophisticated after-burning device designed to complete combustion of the exhaust gases that pass through it. It is a stainless steel container with an inlet and outlet pipe that looks similar to a muffler. Inside, the Catalytic Converter is a ceramic monolithic structure that has honeycomb-like passages running though it. This structure has several sections called beds that are thinly coated with rare metals, which react with the compounds in the exhaust gases to complete the combustion process, thereby cleaning the exhaust of harmful emissions.
  • The first section of the Catalytic Converter is called the reduction bed and is coated with rhodium. It is called the reduction bed because its purpose is to reduce the NOx gases back into harmless nitrogen and oxygen.
  • The next section of the Catalytic Converter is the oxygen storage bed, which is coated with cerium. Its purpose is to maintain an ideal level of oxygen for use by the rear of the converter. It does this by storing and releasing the oxygen that gets released from the reduction of NOx in the previous reduction bed.
  • The oxygen is then available for use in the final oxidizing bed, which is coated with platinum and palladium. The purpose of the oxidizing bed is to complete the combustion of CO by adding oxygen. The oxidizing bed also uses oxygen to burn any of the raw HCs that still remain in the exhaust gases.
P0420 Diagnostic Theory for Shops and Technicians
The P0420 code is set when the Catalyst monitor sees a decrease in voltage from the rear Monitoring Oxygen Sensor(s) and an increase in switching activity-from rich to lean to rich, etc.-that closely resembles the front Oxygen Sensor(s) during the time the computer is activating the Catalytic Converter monitor test. The voltage threshold is usually a minimum of 650 millivolts, which indicates a low level of oxygen. When the voltage goes too far below the 650 millivolt minimum, it indicates a higher level of oxygen. This means that not all of the oxygen is being consumed by the combustion process or by the afterburning effect of the Catalytic Converter. When the oxygen level gets too high, it means that the Cerium or Oxygen storage bed has degraded to the point where it is no longer able to store oxygen created by the reduction of NOx (nitrogen and oxygen). This oxygen is essential for the rear Oxidation bed to complete the conversion of CO into CO2 and HCs into H20 and CO2.
Common Tests for Diagnosis of the P0420 Code
  • Retrieve the code and write down the freeze frame information to be used as a baseline to test and verify any repair.
  • If there are any misfires, ignition, fuel and/or intake problems, these must be repaired before the Catalyst code is addressed. Any misfire, ignition, and/or fuel system problem will quickly ruin a Catalyst. They are often the cause for code in the first place.
  • Test drive the vehicle at or near the freeze frame conditions to verify that the rear Catalyst Monitoring Oxygen sensor is either mirroring the front Oxygen sensor and/or is not reaching the 650 millivolt threshold during 55-60 MPH cruise conditions. If either of theses conditions can be easily verified, then the Catalytic Converter is defective.
  • If there is any doubt about the condition of the front and/or rear Oxygen sensors, then check the Mode 6 data for all the Oxygen sensor monitor tests. If any of the front or rear Oxygen sensors barely pass their Mode 6 tests, then clear all codes and perform a drive cycle to see how well the front and rear Oxygen sensors pass their Mode 6 tests. They need to pass the Mode 6 tests with flying colors or they will confuse the OBD-II diagnostic software and possibly trigger a false code P0420. This is an important concept because if the front Oxygen sensor is slow and barely passes its monitor tests, it can fool the computer into thinking that the Catalyst has failed because the computer just watches how closely the switching speed of the front Oxygen sensor compares to the switching speed of the rear Monitoring Oxygen sensor. If the rear Monitoring Oxygen sensor is losing bandwidth and not able to easily reach the 650 milli volt threshold-but still barely passes its monitor tests-then it, too, can fool the computer into setting a P0420 code.
  • If the Catalyst has failed, be sure to check for any software updates for the power-train computer. Many of the OBD II-equipped vehicles require software updates whenever the Catalyst is replaced

Jun 17, 2014 | 2004 Isuzu Rodeo

1 Answer

Vehicle will not turn over, Catalyst Monitor,Oxygen Sensor Monitor, Oxygen Sensor Heater Monitor, Exhaust Gas Recirculation (EGR) Monitors not completing diagnostics...


if the engine does not spin ck your battery and starter as well as connections, diagnostics on those components cant be completed without the engine running

Aug 31, 2013 | 1997 Chevrolet Tahoe

1 Answer

My check engine light came on with P0422 and P0455 codes. Any suggestions as to the cause.


P0422 - Catalyst below threshold.

Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



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Aug 04, 2010 | 2008 Saturn VUE

1 Answer

2006 Jeep Commander inefficient catalyst


most likely the oxygen sensors (lambada) ,they need changing ,their are two one before the cat and one after,do not think you need a new cat unless it has a min of 150.000 miles on the clock

Jul 02, 2010 | 2006 Jeep Commander

1 Answer

The check engine lamp on my vw jetta 3 is ''on'', i put a diagnostic reader on and it showed the following codes:P0422,P0411,P0300B,P0301B,P0302 and P00172B, what do they mean and how can i solve the...


P0422 - Catalyst below threshold.

Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



Thanks for using FixYa - a 4 THUMBS rating is appreciated for answering your FREE question.!@#$%

May 06, 2010 | 1996 Volkswagen Jetta

1 Answer

I have a 1997 hyundai elantra and i have three code problems what are they and what do i need to do to fix them. p0422, p0442,p0446


P0422 - Catalyst below threshold.

Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



Thanks for using FixYa - a 4 THUMBS rating is appreciated for answering your FREE question.#$@!

Feb 20, 2010 | 1997 Hyundai Elantra

1 Answer

Vsc and check engine light is on . Had it read and code p0420 came up. Autozone said it could be an air leak in exhaust, AF sensor error, fuel system fault or faulty catalytic converter. Is there a cheap...


DTC P0420: Catalyst System Efficiency Below Threashold (Bank 1)

The ECM uses sensors mounted before and after the three-way catalyst (TWC) to monitor its efficiency. The first sensor, and Air Fuel ratio (A/F) sensor, sends pre-catalyst A/F ratio information to the ECM. The second sensor, a heated oxygen sensor (O2S), sends post-catalyst information to the ECM. The ECM compares these two signals to judge the efficiency of the catalyst and the catalyst's ability to store oxygen. During normal operation, the TWC stores and releases oxygen as needed. The capacity to store oxygen results in a low variation in the post-TWC exhaust stream as shown below.
If the catalyst is functioning normally, the waveform of the heated oxygen sensor slowly switches between RICH and LEAN. If the catalyst is deteriorated, the waveform will alternate frequently between RICH and LEAN. As the catalyst efficiency degrades, its ability to store oxygen is reduced and the catalyst output becomes more variable. When running the monitor, the ECM compares sensor 1 signals (A/F sensor) over a specific amount of time to determine catalyst efficiency. The ECM begins by calculating the signal length for both sensors (for the rear oxygen sensor, the ECM uses the output voltage signal length). If the oxygen sensor output voltage signal length is greater than the threshold (threshold is calculated based on the A/F sensor signal length), the ECM concludes that the catalyst is malfunctioning. The ECM will turn on the MIL and a DTC will be set.
Hope this helps :)

Oct 19, 2009 | 2005 Toyota Highlander

1 Answer

1999 beetle P0422 which O2 is bad the o2 before the cat or after


P0422 - Catalyst below threshold.

Catalytic converter is clogged or out of medium.

Replace it.


ACTUAL DIAGNOSTIC:

Fault Code Definition
Code P0422 indicates that the Bank 1 Main Catalytic Converter's emissions efficiency has fallen below the minimum allowable limit. This threshold is tracked by a Catalyst Monitoring Oxygen Sensor located on or near the outlet of the Catalytic Converter.

Symptoms

* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed

Common Problems That Trigger the P0422 Code

* Defective Catalytic Converter
* Engine misfires have damaged the Catalytic Converter
* Internal engine damage resulting in high oil consumption and/or a leaking Head gasket has damaged the Catalytic Converter

Common Misdiagnoses

* Oxygen Sensors are replaced when the real problem is a damaged Catalyst
* Catalyst is replaced when the real problem is internal engine damage, which is producing elevated emissions levels
* Catalyst is replaced when a misfiring engine is the real problem



Thanks for using FixYa - a 4 THUMBS rating is appreciated for answering your FREE question.

Jan 27, 2009 | 1999 Volkswagen Beetle

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