The thermostat may fail to close completely, causing the Check Engine Light to illuminate. This problem will prevent the engine from reaching normal operating temperature; a new thermostat should be installed.Google+
Car Problem Reports
Jeep Grand Cherokee Check Engine Light Due to Failed Thermostat
Jeep Grand Cherokee Problem
Engines Affected: 3.7L V6, 5.7L V8 HEMI
Average Mileage: 60,000 mi (52,000 mi - 68,000 mi)
Visitor, 2009 Jeep Grand Cherokee, 3.7L V6, 68,000 mi
Changed thermostat 3 times already due to first overheating. Second time the engine does not warm up to right temperature causing check engine to come on. Thermostat replaced 2nd time and engine still did not operate right causing check engine lamp to come on again. Replaced thermostat again and now waiting to see if it will operate correctly this time.
This problem began at 68,000 miles. My jeep only has 72,000 now.
Visitor, 2006 Jeep Grand Cherokee, 5.7L V8 HEMI, 52,000 mi