14390 - SPECIAL COVERAGE. ON SOME 2012-2014 MODEL YEAR CHEVROLET TAHOE VEHICLES EQUIPPED WITH RPO PPV OR 5W4, UNDER CERTAIN OPERATING CONDITIONS, SOME POLICE PACKAGE VEHICLES HAVE EXPERIENCED INFREQUENT ENGINE-IDLE PROBLEMS AND MOMENTARY POOR LOW-SPEED ENGINE PERFORMANCE. THESE PERFORMANCE ISSUES CAN BE TRIGGERED IF BOTH OF THE FOLLOWING CONDITIONS ARE SATISFIED: (I) THE VEHICLE IS OPERATED IN AMBIENT TEMPERATURES THAT EITHER EXCEED 100 DEGREES FAHRENHEIT IN A LOW-HUMIDITY ENVIRONMENT OR THAT EXCEED 85 DEGREES FAHRENHEIT IN A HIGH-HUMIDITY ENVIRONMENT; AND (II) THE VEHICLE IS OPERATED AT IDLE FOR A LONG PERIOD OF TIME, AT IDLE AFTER HEAVY POWERTRAIN USAGE, OR WITH A HEAVY ELECTRICAL LOAD. THE CONDITION CAUSES ENGINE-IDLE RPM FLUCTUATIONS (450-1000 RPM) AND HESITATION DURING ACCELERATION. WHILE GM HAS RECEIVED SOME FIELD REPORTS OF ENGINE STALLS AT IDLE, GM HAS NOT BEEN ABLE TO CONFIRM THESE REPORTS. GM HAS ONLY BEEN ABLE TO DUPLICATE A SIMILAR STALL BY OPERATING A TEST VEHICLE AT A TEMPERATURE THAT IS AT THE LIMIT OF THE FUELÂ’S HIGH-TEMPERATURE SPECIFICATION. IF SUCH A STALL DID OCCUR, THE STALL WOULD BE AT IDLE OR LOW SPEED, AND ALL ELECTRICAL AND SAFETY SYSTEMS WOULD CONTINUE TO FUNCTION AS DESIGNED. IF THE CONDITION OCCURS WITHIN THE SPECIAL COVERAGE TERMS, DEALERS ARE TO UPDATE THE ENGINE CONTROL MODULE (ECM) AND BODY CONTROL MODULE CALIBRATIONS.
