# P0420 on the 2012 GMC Sierra

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

Nobody has written a description of this code yet.

## Bulletins for this model year that name P0420

- [10156912](https://open.wenmarpro.com/bulletins/10156912), 2019-04-08: This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that may have a Service Engine Soon Malfunction Indicator Lamp on at low mileage. Technician may find Diagnostic Trouble Codes P0420 and or P0430 stored. Technician should be advised that the catalytic converter efficiency Diagnostic Trouble Codes P0420 and P0430 are disabled for the first hour of engine run time to allow break\-in of the catalytic converter. Technician will need to use a Tech2 to check the verify engine run time on the Engine Hour Meter in the Instrument Panel Cluster Data Display/Data 1 List in the scan tool match. If the engine run time is less than one hour, the battery may have been disconnected, or another vehicle power loss event may have occurred, during vehicle manufacturing. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle. If the catalytic converter was replaced and the Diagnostic Trouble Codes set it may be a result of the engine run time restrictions no longer being in place since the vehicle is no longer new. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle.
- [10125973](https://open.wenmarpro.com/bulletins/10125973), 2017-12-22: This Preliminary Information communication provides information to the technician about vehicles that may have Malfunction Indicator Lamp on. Technician may find Diagnostic Trouble Code P0420, P24A0 and or P2463. Technician should follow published Service Information diagnostics for the Diagnostic Trouble Codes that are set. If the diagnostic leads to diagnosis or replacement of the Q57 Indirect Exhaust After\-treatment Fuel Injector, document all of your test results. If Diagnostic Trouble Codes P0420, P24A0 and/or P2463 are found, inspect the inlet and outlet of the Diesel Oxidation Catalyst for signs of damage, if damage is found replace the Diesel Oxidation Catalyst.
- [10114614](https://open.wenmarpro.com/bulletins/10114614), 2017-08-15: This Preliminary Information communication provides information to the technician of additional information while diagnosing a diagnostic trouble code P0420. Check for a possible leak in the exhaust system behind the bank one number 2 oxygen sensor. If a leak is found or there is an aftermarket utility bed or trailer hitch installed. Check for a minimum clearance of 1.5 to 2 inches of the exhaust system. Install a new clamp and torque it to 40.5 foot pounds.
- [10114599](https://open.wenmarpro.com/bulletins/10114599), 2017-08-15: This Preliminary Information communication provides information to the technician with additional information while diagnosing a diagnostic trouble code P0420. Check for a possible leak in the exhaust system behind the bank one number 2 oxygen sensor. If a leak is found or there is an aftermarket utility bed or trailer hitch installed. Check for a minimum clearance of 1.5 to 2 inches of the exhaust system. Install a new clamp and torque it to 40.5 foot pounds.
- [10113325](https://open.wenmarpro.com/bulletins/10113325), 2017-08-15: This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that may have a Service Engine Soon Malfunction Indicator Lamp on at low mileage. Technician may find Diagnostic Trouble Codes P0420 and or P0430 stored. Technician should be advised that the catalytic converter efficiency Diagnostic Trouble Codes P0420 and P0430 are disabled for the first hour of engine run time to allow break\-in of the catalytic converter. Technician will need to use a Tech2 to check the verify engine run time on the Engine Hour Meter in the Instrument Panel Cluster Data Display/Data 1 List in the scan tool match. If the engine run time is less than one hour, the battery may have been disconnected, or another vehicle power loss event may have occurred, during vehicle manufacturing. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle. If the catalytic converter was replaced and the Diagnostic Trouble Codes set it may be a result of the engine run time restrictions no longer being in place since the vehicle is no longer new. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle.
- [10113059](https://open.wenmarpro.com/bulletins/10113059), 2017-08-15: This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that may have a Service Engine Soon Malfunction Indicator Lamp on at low mileage. Technician may find Diagnostic Trouble Codes P0420 and or P0430 stored. Technician should be advised that the catalytic converter efficiency Diagnostic Trouble Codes P0420 and P0430 are disabled for the first hour of engine run time to allow break\-in of the catalytic converter. Technician will need to use a Tech2 to check the verify engine run time on the Engine Hour Meter in the Instrument Panel Cluster Data Display/Data 1 List in the scan tool match. If the engine run time is less than one hour, the battery may have been disconnected, or another vehicle power loss event may have occurred, during vehicle manufacturing. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle. If the catalytic converter was replaced and the Diagnostic Trouble Codes set it may be a result of the engine run time restrictions no longer being in place since the vehicle is no longer new. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle.
- [10112995](https://open.wenmarpro.com/bulletins/10112995), 2017-08-15: This Preliminary Information communication provides information to the technician of additional information while diagnosing a diagnostic trouble code P0420. Check for a possible leak in the exhaust system behind the bank one number 2 oxygen sensor. If a leak is found or there is an aftermarket utility bed or trailer hitch installed. Check for a minimum clearance of 1.5 to 2 inches of the exhaust system.
- [10112974](https://open.wenmarpro.com/bulletins/10112974), 2017-08-15: This Preliminary Information communication provides information to the technician about vehicles that have a Service Engine Soon Malfunction Indicator Lamp on. Technician will find Diagnostic Trouble Code P0420. Technician will need to follow published Service Information diagnostics. Technician will check for a possible leak in the exhaust system behind the bank 1 sensor 2 O2 sensor. Technician will need to reposition the exhaust clamp or replace with a wider band clamp.
- [10112842](https://open.wenmarpro.com/bulletins/10112842), 2017-08-15: This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that may have a Service Engine Soon Malfunction Indicator Lamp on at low mileage. Technician may find Diagnostic Trouble Codes P0420 and or P0430 stored. Technician should be advised that the catalytic converter efficiency Diagnostic Trouble Codes P0420 and P0430 are disabled for the first hour of engine run time to allow break\-in of the catalytic converter. Technician will need to use a Tech2 to check the verify engine run time on the Engine Hour Meter in the Instrument Panel Cluster Data Display/Data 1 List in the scan tool match. If the engine run time is less than one hour, the battery may have been disconnected, or another vehicle power loss event may have occurred, during vehicle manufacturing. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle. If the catalytic converter was replaced and the Diagnostic Trouble Codes set it may be a result of the engine run time restrictions no longer being in place since the vehicle is no longer new. Technician will need to clear the Diagnostic Trouble Codes and perform a drive cycle.
- [10112733](https://open.wenmarpro.com/bulletins/10112733), 2017-08-15: This Preliminary Information communication provides information to the technician that engineering is asking for additional information if SI diagnosis leads to replacement of the Indirect Fuel Injector for a P0420 Diagnostic Trouble Code. Technician should follow published Service Information diagnostics for Diagnostic Trouble Code P0420. Technician will need to also gather quantity of fuel flow measured, engine hours, type of vehicle, and estimated percentage of time the vehicle spends at idle.