P1491 DODGE - Radiator Fan Relay Circuit Condition Possible causes Faulty Radiator Fan Control Relay Radiator Fan Control Relay harness is open or shorted Radiator Fan Control Relay circuit poor electrical connection What does this mean? When is the code detected? The Powertrain Control Module (PCM) has detected an open or shorted condition in the radiator fan relay circuit Possible symptoms Engine Light ON (or Service Engine Soon Warning Light) P1491 Dodge Description With the key on or engine running, system voltage over 10v, fan relay commanded on, the Powertrain Control Module (PCM) detects a shorted or open condition in the relay control circuit. Test the fan relay resistance (it should be 30-70 ohms). Refer to code repair chart in other manuals or media.