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

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 Sensor(s) 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

The starter is computer controlled by way of a relay ! When you turn the key to the start position a low voltage signal is send to the BCM - body control module , the BCM then sends a message over the GMLAN serial data network to the PCM for starter engagement , The PCM energizes the starter relay sending B+ voltage to the starter solenoid ,if there are no anti-theft system problems. The codes you have listed are emission related codes !
DTC P0455: Evaporative Emission (EVAP) System Large Leak
You must mean P0442 , because there isn't a code P0422 .
DTC P0442: Evaporative Emissions (EVAP) System Small Leak Detected
None of these would cause vehicle to shut down > Your best bet would be to take your vehicle to qualified repair shop an have diagnostics run on it .

large evap leak --check gas cap that it is on --look under truck at rear of fuel tank by spare tire and check the evap canister and hoses the following link will assist you
https://www.obd-codes.com/p0455 How to Fix Check Engine Light P0455 Emissions Purge Valve Replacement How to Fix Check Engine Light P0455 Emissions Purge Valve Replacement

Hi.

P0455 is for a evap system large leak detected, and P0422 is main catalyst efficiency below threshold.

Get the cat checked out, this could be the cause of both codes. Failing that a smoke test is your best bet to determine exactly where the evap system is leaking from.

You may need a shop manual or a shop to fix it.
Code 455 is a large leak in the EVAP system, and code 422 is a problem with the catalytic converter.
The EVAP leak could be any number of things including the gasket on top of the tank for the fuel pump. The gas tank needs to be pressure tested to look for the leak and that takes special equipment.
And the computer does not think the cat is performing within specs based on the readings from the O2 sensors.

What code ? P0442 or P0456 or p0455
DTC EVAP P0442 P0455 P0456
EVAP Leaks P0442 and P0455

Wells EVAP Training with Sgt Tech P0440 P0441 P0442 etc

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


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P0422 Buick - 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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First of all, these codes are what are called "Powertrain Trouble Codes' (that's what the "P" means P=Powertrain). TCM Request (Transmission Control Module = TCM). The request was to turn on the 'Check Engine" light.
P0720 - output speed sensor circuit malfunction
P0715 - Input speed sensor (turbin speed) circuit malfunction
P0442 - Evaporative Emission System Leak (Small Leak)
P0455 - Evaporative Emission System Leak (Large Leak)
Check fuel filler cap problems - for Evap Emiss leaks
Replace the pulse generators & have the trans fluid replaced/flushed.
The Main Catalyst System Efficiency Bank 1 Is P0420, not P0442
If you had P0420 code, the catalytic converter is shot... and that's an expensive component.

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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