Some 2006 Chevy Cobalts and HHRs with 2.2-liter engines (VINs D and F) may turn on the check engine light and log one or more of the following trouble codes in computer memory: P0128, P0326, P0420, P0604, P0717 and P2431.
GM says it's unlikely that any drivability symptoms will be present when the check engine light illuminates, and it attributes the condition to software issues in the PCM.
Flashing the module with updated calibration files is the only remedy.
Check with a dealer for the specifics of the reprogramming job.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via email at [email protected].