What is the catalyst system - 1997 Chevrolet C1500

The diagnostic trouble code (DTC) P0420 "Catalyst System Efficiency Below Threshold" is one possible outcome following the Catalytic Converter Monitor (test). This monitor is one of the last tests to be performed by the powertrain control module (PCM) because other failures in the system could compromise this test's result. Catalyst efficiency is tested by observing the oxygen sensor signals both before and after the catalyst. Before the catalyst, the signal should appear as a sine wave as it switches back and forth between rich (0.9 volts) and lean (0.1 volts). After the catalyst, the signal should be flat-lined on the rich side (about 0.7 volts). This is because a healthy catalyst will store oxygen and therefore remove the "lean" portion of the signal/waveform. If the signal after the catalyst still appears as a sine wave, the PCM concludes that the catalyst can no longer store oxygen and should therefore be replaced. In your specific scenario where a downstream (post-cat) O2 sensor was just replaced, I would theorize that this sensor had failed and was flat-lined. Then when it was replaced two things happened: 1.) the oxygen sensor began to work properly which allowed the oxygen sensor monitor (test) to complete, and 2.) the catalyst monitor then ran and used the new (accurate) sensor data to determine that the catalyst efficiency was below threshold. You can read more here: https://www.yourmechanic.com/article/p0420-obd-ii-trouble-code-catalyst-system-efficiency-below-threshold-bank-1-by-jamahl-walker

Got it scanned and it's P0420: Catalyst efficiency below thresholdbank 1. They said it could be a bad catalytic converter or oxygen sensor. I borrowed a scanner and tried to measure the oxygen sensor readings over time.Sep 8, 2011


civic - Check Engine code P0420 Catalyst efficiency below ...

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P0420 Error Code: Catalyst System Efficiency Below ...

www.obd-codes.com/p0420
P0420 OBD-II Trouble Code. Technical Description. Catalyst System Efficiency Below Threshold (Bank 1). What does that mean? This diagnostic trouble code ...

P0420 Code Fix How Its Done Catalyst Efficiency Below ...

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Here is a tutorial on P0420 code fix catalyst efficiency below threshold How To Diagnose a p0420 code ...

P421=Warm up catalyst system efficiency below threshold, bank 1
P431=Warm up catalyst system efficiency below threshold, bank 2
Sounds like you may have clogged or damaged catalyst converters or bad 02 sensors.
Those codes I think are taking from after the catalyst by the sensors in the exhaust pipes. Be careful taking it to a mechanic for further checking since the catalyst converters are not cheap through them. If you need to replace the converters, shop around and get prices on aftermarket parts. Don't be ripped off by a hungry mechanic or especially a dealer.

EXHAUST RELATED ERROR CODES

There are 711 possible PO generic DTC error codes. Only 7 of the 711 codes are exhaust related.

PO401: Insufficient EGR Flow

PO402: Exhaust Gas Recirculation (EGR) Excessive Flow Detected

PO410: Secondary Air Injection System Malfunction

PO420: Catalyst System Efficiency Below Threshold (Bank 1)

PO421: Warm-Up Catalyst Efficiency Below Threshold (Bank 1)

PO430: Catalyst System Efficiency Below Threshold (Bank 2)

PO431: Warm-Up Catalyst Efficiency Below Threshold (Bank 2)

THINGS TO ASK YOURSELF OR YOUR CUSTOMER

Have there been any driveability or performance issues with the vehicle, have there been any recent repairs or tune-up work performed, if so was the check engine light reset and were the codes recorded on previous repair orders.

Do not rely on scan tool data alone. In most applications, the customer will have the check engine light reset prior to repair. If the original cause of converter failure is intermittent, only the catalyst failure code may show up

Hi there:

DTC P0422 - Main Catalyst Efficiency Below Threshold (Bank 1)
A vehicles' catalytic converter (catalyst) helps improve tailpipe emissions by oxygenating the exhaust gasses. It helps convert hydrocarbons (HC), Carbon Monoxide (CO), and oxides of Nitrogen (NOx) into water vapor (H20), Carbon Dioxide (CO2), and Nitrogen (N).

The PCM (Powertrain control module) monitors the catalyst efficiency by means of a post-catalyst Oxygen sensor. This sensor is used primarily for this purpose. It should switch much slower than the front oxygen sensors. If at any point the PCM detects that the post-catalyst o2 sensor is switching too rapidly (indicating no change between the inlet and outlet of the catalytic converter) it interprets this as a catalyst that isn't functioning properly.

Bank 2 is the side of the engine that has cylinder #1.


Symptoms of a P0422 DTC may include:
Increased tailpipe emissions
MIL (Malfunction Indicator Lamp) illumination


Potential causes of a P0422 code include:
Bad or non-functional catalyst
Engine operating out of optimal air:fuel ratio

Possible Solutions:
Catalytic converters contain precious metals like platinum, palladium, rhodium among others. Basically, the cheaper the cat, the less precious metals used. It should be noted that there are some automobile makes that are very finicky when it comes to catalytic converters and the logic that the PCM uses to monitor them. Just because the parts guy says it will work doesn't mean that it will. The reason is that the engineering of the vehicle was done with a high quality catalyst in mind and it can't be replaced with a low cost catalyst. There are also different kinds of catalysts. Some makes will allow for a cheaper catalyst while others simply will not. Toyotas & Subarus are the most notorious for this. Subarus require CARB certified catalysts to keep the check engine light off and won't tolerate an aftermarket catalyst, no matter how expensive.

So basically if you have a recurrence of this code after replacing the catalyst with an aftermarket catalyst, this may be your problem. If you have this code and haven't replaced the cat, there's basically two likely causes: The catalyst is no good, or the engine is running out of optimal air:fuel ratio. A tune up or engine repair may correct it. Otherwise you'll need to replace the catalyst.


DTC P0455 - Evaporative Emission Control System Leak Detected (no purge flow or large leak)
This indicates a fuel vapor leak or lack of purge flow in the EVAP control system. It means a large leak has been detected. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

A code p0455 most likely means one or more of the following has happened:
A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
Other leak or damaged piece in EVAP system

Possible Solutions: with a p0455, the most common repair is to:
Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
Otherwise, replace the gas cap, and/or
Inspect the EVAP system for cuts/holes in tubes/hoses (you may hear a vacuum noise or smell fuel), repair if necessary


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Intervention Regeneration Strategy - EVIC
Message Process Flow (Catalyst Full Message)
(6.7L Diesel Engines Only)

Your new Cummins 6.7L diesel meets all EPA Heavy
Duty Diesel Engine Emissions Standards, resulting in the
lowest emitting diesel engine ever produced.
To achieve these emission standards your vehicle is
equipped with state of the art engine and exhaust system.
The engine and exhaust aftertreatment system work
together to achieve the EPA Heavy Duty Diesel Engine
Emissions Standards. These systems are seamlessly integrated
into your vehicle and managed by the Cummins
6.7L engine Powertrain Control Module (PCM). The PCM
manages engine combustion to allow the exhaust system's
catalyst to trap and burn Particulate Matter (PM)
pollutants, with no input or interaction on your part.
Additionally, the overhead console in your vehicle has
the ability to alert you to additional maintenance required
on your truck or engine. Refer to the following
messages that may be displayed on your Electronic
Vehicle Information Center (EVIC):

WARNING!
A hot exhaust system can start a fire if you park over
materials that can burn. Such materials might be
grass or leaves coming into contact with your exhaust
system. Do not park or operate your vehicle in areas
where your exhaust system can contact anything that
can burn.

Perform Service
The 6.7L Cummins engine utilizes a Closed Crankcase
Ventilation (CCV) system, EGR Valve and a EGR Cooler.
This system filters and recycles gasses produced in the
crankcase during the normal combustion process. Perform
Service will be displayed on the overhead console of
your vehicle if the CCV filter, EGR Valve and EGR Cooler
is due for required maintenance. The CCV filter is located
on the top of the engine valve cover. For additional
information, see your local authorized dealer.
Catalyst Full See Owner Manual
Catalyst Full See Owner Manual will be displayed on the
overhead console of your vehicle if the exhaust particulate
filter reaches 80% of its maximum storage capacity.
Under conditions of exclusive short duration and low
speed driving cycles, your Cummins engine and exhaust
aftertreatment system may never reach the conditions
required to remove the trapped PM, if this occurs Catalyst
Full See Owner Manual will be displayed on the
overhead console in your vehicle. If this message is
displayed you will hear one chime to assist in alerting
you of this condition.
Catalyst Stat::::::::::80%
Catalyst Stat::::::::::80% will replace the message Catalyst
Full See Owner Manual after it is displayed for one
minute. The engine Powertrain Control Module (PCM)
will continue to monitor the amount of particulate matter
trapped in the particulate filter. This message indicates
the percentage of the particulate filter capacity that has
been used.

By simply driving your vehicle at highway speeds for as
little as 45 minutes you can remedy the condition in the
particulate filter system and allow your Cummins engine
and exhaust Aftertreatment system to remove the
trapped PM and restore the system to normal operating
condition.
Catalyst Stat:::::::::::80%, 90%, 99%
Catalyst Stat:::::::::::80%, 90%, 99% If you are unable to
drive your vehicle under these conditions for an extended
period of time after the initial warning notification,
the Engine PCM will continue to monitor the
particulate filter and will display the progression of
particulate filter usage (80, 90, 99%) on the EVIC message
center.

CATALYST FULL SERVICE REQD
If the particulate filter reaches 99% of it's capacity the
overhead console in your vehicle will chime twice and
display the message CATALYST FULL SERVICE REQD.
At this point the engine PCM will register a fault code,
the instrument panel will display a MIL light and the
engine PCM will derate the truck reducing its horsepower
and torque output.
The PCM derates the engine in order to limit the likelihood
of permanent damage to the aftertreatment system.
If this condition is not corrected and a dealer service is
not performed, extensive exhaust aftertreatment damage
can occur. In order to correct this condition it will be
necessary to have the truck serviced by your local
authorized dealer.

Hi and welcome to FixYa!

Code p0420 means Catalyst System Efficiency Below Threshold (Bank 1). This will surely needs attention to resolve the problem.

Hope this helps and thank you for using FixYa! Have a good one!

P0420 TW (Two-Way) Catalyst System, Bank 1
P0430 TW Catalyst System, Bank 2 . most likely a new catalytic converter.

Thanks. keep updated for any more query.you can rate this solution and show your appreciation.

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 :)

If you have an exhaust leak before or after the catalytic convertor, then the response of the of the sensor could be slowed.

An excerpt from Wikipedia:
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Location of the probe in a system
The probe is typically screwed into a tapped hole in the exhaust, located after the branch manifold of the exhaust system combines, and before the catalytic converter. New vehicles are required to have a sensor before and after the exhaust catalyst to meet U.S. regulations requiring that all emissions components be monitored for failure. Pre and post-catalyst signals are monitored to determine catalyst efficiency. Additionally, some catalyst systems require brief cycles of lean (oxygen-containing) gas to load the catalyst and promote additional oxidation reduction of undesirable exhaust components.
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It's a good article about the two-sensor system and oxygen sensors in general and is available here:

http://en.wikipedia.org/wiki/Oxygen_sensor