P0420 GMC - Catalyst System Low Efficiency Bank 1
P0420 GMC Possible Causes
- Faulty Three-way Catalyst Converter Bank 1
- Exhaust Tube
- Intake Air Leaks
- Faulty Oxygen (O2) Sensor
- Faulty Fuel injector(s)
- Leaking Fuel Injector (s)
- Faulty Spark plugs
- Improper Ignition Timing
- Faulty Engine Control Module (ECM)
- Dirty Air Filter
How is the P0420 GMC code repair?Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
What is the cost to diagnose the P0420 GMC code
Labor: 1.0The cost to diagnose the P0420 GMC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
How much do you know about cars?
Take the AutoCodes.com automotive tests and turbo-charge your car repair knowledge
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.
- Engine Light ON (or Service Engine Soon Warning Light)
P0420 GMC MeaningIn 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.
More InformationNeed more information on how to fix the P0420 GMC code?
Get Access to Factory Service Manuals