Some 2009 1500-series Dodge Ram Trucks built before Oct. 3, 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.
Some 2002-07 S-Type, 2003-06 XK8, 2004-07 XJ and 2007 XK models may produce a chirping noise from the front of the engine. Jaguar says the noise usually occurs during a cold start, and attributes it to the serpentine drive belt not tracking correctly among the various pulleys.
The fix depends on whether the engine is naturally aspirated or supercharged. For conventional engines, replace the original idler pulley and drive belt with upgraded designs, part No. C2C 37064 and part No. C2C 37063, respectively. For supercharged engines, replace the following with updated parts: belt tensioner (part No. C2C 37057), idler pulley (part No. C2S 46862), idler pulley bracket (part No. C2C 37056) and drive belt (part No. C2C 37055).