Chrysler Repair: emissions, radiator fan, chrysler town

Question
My 1999 Chrysler Town&Country did not pass emissions and wanted to know what does diagnostic code p1491 mean

Answer
P-1491 RADIATOR FAN CONTROL RELAY CIRCUIT

Set Condition: The intake air sensor circuit voltage at PCM cavity 37 goes above 4.9 volts.
POSSIBLE CAUSES
IAT SENSOR DEFECTIVE
IAT SENSOR SIGNAL CIRCUIT OPEN
SENSOR GROUND CIRCUIT OPEN
IAT SENSOR WIRING HARNESS INTERMITTENT DEFECT
IAT SENSOR WIRING HARNESS OBSERVABLE DEFECT
PCM DEF (IAT SENSOR)