Some 2009 1500-series Dodge Ram Trucks built before Oct. 30, 2008 and Jeep Grand Cherokees and Commanders built before Oct. 28, 2008 (all with 5.7-liter engines) may exhibit spark knock or pinging under acceleration.
According to Chrysler, the noise is most noticeable in the 1800-2500 rpm range, and is caused by too much spark advance being dialed in by the PCM. Reprogramming the module with updated software is the only sure-fire fix.
Check with a dealer for the specifics of the flash.
"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 e-mail at [email protected].