GMC Yukon 2000–2006

▸Known issuesP0420 / P0430 on a new or just-replaced catalytic converter (break-in not completed)1

1. Manufacturer communication2002–2006 GMC YUKON DENALI ・ 2019-04-08(4 earlier editions of this document folded here)

   Service Engine Soon Lamp at Low Mileage

   1. 1Fault

      • Warning light
      • Check engine / Service Engine Soon
      • P0420
      • P0430
      • An SES light may come on on low mileage vehicles or vehicles that recently had the catalytic converter replaced, with DTCs P0420 and/or P0430 stored.
      ↓→

   2. 2Finding the cause

      • Catalytic Converter: failed

      Possible causes

      • On a new vehicle, catalytic converter efficiency DTCs P0420 and P0430 are disabled for the first hour of engine run time to allow break-in of the catalytic converter.
      • 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.
      • If the DTCs set shortly after the catalytic converter is replaced, it may be because the engine run time restrictions are no longer in place since the vehicle is no longer new.
      • As a result, the catalytic converter may not have completed a thorough break-in cycle after replacement, possibly resulting in a false DTC P0420 and/or P0430.

      Steps to confirm (in the document’s order)

      1. On a new/low mileage vehicle with these DTCs, use the Tech 2 to verify engine run time on the Engine Hour Meter in the IPC Data Display/Data 1 List.
      2. Finally, restart the engine and operate the vehicle at the conditions for running the DTC P0420/430 tests, and make sure the vehicle passes them.
      ↓→

   3. 3Correction

      Repair

      1. Clear the DTCs and perform the drive cycle given in the document.
      2. Drive cycle step: drive the vehicle at sustained highway speed for 25 to 30 minutes.
      3. Drive cycle step: restart the engine and resume highway speed for an additional 10 to 15 minutes.
      4. If the diagnostics do not pass, perform SI diagnostics and repair as necessary.
   Read the sentences of the record

   From the manufacturer’s document

   • Applies to：Applies to GMC Yukon models, 2002 - 2018, with a V8 engine.
   • Condition：An SES light may come on on low mileage vehicles or vehicles that recently had the catalytic converter replaced, with DTCs P0420 and/or P0430 stored.
   • Cause：On a new vehicle, catalytic converter efficiency DTCs P0420 and P0430 are disabled for the first hour of engine run time to allow break-in of the catalytic converter.
   • Confirm：On a new/low mileage vehicle with these DTCs, use the Tech 2 to verify engine run time on the Engine Hour Meter in the IPC Data Display/Data 1 List.
   • Cause：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.
   • Cause：If the DTCs set shortly after the catalytic converter is replaced, it may be because the engine run time restrictions are no longer in place since the vehicle is no longer new.
   • Cause：As a result, the catalytic converter may not have completed a thorough break-in cycle after replacement, possibly resulting in a false DTC P0420 and/or P0430.
   • Repair：Clear the DTCs and perform the drive cycle given in the document.
   • Repair：Drive cycle step: drive the vehicle at sustained highway speed for 25 to 30 minutes.
   • Repair：Drive cycle step: restart the engine and resume highway speed for an additional 10 to 15 minutes.
   • Confirm：Finally, restart the engine and operate the vehicle at the conditions for running the DTC P0420/430 tests, and make sure the vehicle passes them.
   • Repair：If the diagnostics do not pass, perform SI diagnostics and repair as necessary.

   Open the manufacturer’s document (PDF) ↗ The points above were read from this document.

   Remedy

   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.