TSB's

Cat converter break-in

This TSB applies to 2004-2012 Cadillac Escalade and Escalade Hybrid, 2004-2012 Chevy Avalanche, Express, Silverado, Silverado Hybrid, Suburban, Tahoe and Tahoe Hybrid, 2004-2012 GMC Savana, Sierra, Sierra Hybrid, Yukon and Yukon Hybrid, 2003-2009 Hummer H2 and 2008-2009 Hummer H3 vehicles. This TSB relates to catalytic converter break-in information to prevent DTCs P0420 and/or P0430.

A SES light may be experienced on low mileage vehicles or vehicles that have recently had the catalytic converter replaced.

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. The following scenarios may allow a DTC to set after this hour of engine run time has expired.

  1. If these DTCs are found on a new/low mileage vehicle, use the Tech 2 to verify engine run time on the Engine Hour Meter in the IPC Data Display/Data 1 List. 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. This may allow the catalyst efficiency diagnostics to run before one hour of engine run time has been achieved. If this occurs, the catalytic converter may not have completed a thorough break-in cycle, causing a false DTC P0420 and/or P0430 to set. If this occurs, clear the DTCs and perform the following drive cycle.
  2. If the DTCs set shortly after the catalytic converter is replaced, it may the a result of the engine run time restrictions no longer being 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. If this occurs, clear the DTCs and perform the following drive cycle.

In order to achieve proper catalytic converter temperature and allow the mat material to out-gas (break-in), perform the following drive cycle:

  1. Drive the vehicle at sustained highway speed for 25 to 30 minutes.
  2. Bring the vehicle to a stop.
  3. Shut off the engine for one minute.
  4. Restart the engine and resume highway speed for an additional 10 to 15 minutes.
  5. Bring the vehicle to a stop.
  6. Shut off the engine for one minute.
  7. Restart the engine and operate the vehicle at the conditions for running the DTC P0420/P0430 tests and assure that the vehicle passes these diagnostic tests. If the diagnostics for DTCs have passed, return the vehicle to the customer. If the diagnostics do not pass, perform SI diagnostics and repair as necessary.
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