P0420 GMC - Catalyst System Low Efficiency Bank 1
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Possible causes
- Three way catalyst converter Bank 1
- Exhaust tube
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Powertrain Control Module (PCM)
What does this mean?
Tech notes
As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first.
What does this mean?
When is the code detected?
If a condition exists which causes the Powertrain Control Module (PCM) to detect excessive Bank 1 HO2S #2 activity outside of an acceptable range for an extended period of time, the PCM will set the P0420 code. This indicates that the three-way catalytic converters oxygen storage capacity is below a threshold considered acceptable.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P0420 GMC Description
In order to maintain a reasonably low emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), the engine controls system uses a three-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and Carbon Dioxide. The catalyst also reduces NOx, converting it to Nitrogen. The Powertrain Control Module (PCM) monitors this process using Bank 1 HO2S #2. Bank 1 HO2S #2, located in the exhaust stream past the three-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signal will be far less active than that produced by Bank 1 HO2S #1.
SOURCE: check engine!
normally you need to change the converter if you have smog test you have no choise if not disconnect the battery for a minute and try it out hopefully it will not come back hope its a fixya thanks for the post pierre
SOURCE: 2001 gmc yukon xl 1500
Check to see if the power steering pump is still turning. If you have a broken drive belt (serpentine belt or "fan" belt), and the pump doesn't turn, you have no power assist. If the pump is still turning, check the fluid level in the reservoir.
SOURCE: 2002 YUKON DANALI XL I THINK I RAN OUT OF GAS
try to put 2 gal of gas.
if you run out of gas, the system require little more than a gal of gas to get from the pump in the tank through the filter to the injector. Approximately 1gal just to pressured the fuel rail.
SOURCE: receiving engine code p0420 on my 2005 altima 2.5 s
A p0420 code indicates a Catalytic System efficiency failure, Bank 1.
Basically, the computer is seeing reduced efficiency of the catalytic converter or one of it's components (such as an 02 sensor)
There may be a few root causes, such as a faulty oxygen sensor, faulty coolant temperature sensor, faulty converter, Large exhaust leak, or retarded (slow) timing.
SOURCE: 2002 GMC YUKON XL 1500 MOTOR DIES AFTER GOING
Check the fuel cap!! If the vacuum relief is not working it can impede the fuel flow and cause the engine to shut down or not restart after a stop. Waiting usually gives things a chance to stabalize and the engine will restsrt. When this happens again try loosening the cap and see if the engine will restart.....If it restarts immediately, REPLACE the fuel cap..Do Not leave it loose because this will cause other problems. If it is not the fuel cap the problem may be the filter, the fuel pump, or aome other fuel system malfunction.
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