Jeep Liberty Radiator Repair Manual
Summit Racing
Reinie answered 2 years ago I've been driving with P1491 for a couple of months and haven't had any overheating, but it is winter in Chicago. P1491 means the powertrain control module (PCM) can't communicate with the fan relay circuit. The service manual says to check for an open or a ground between the two. My guess it could also be that the relay is fried which can happen if the radiator fan pulls too much current (40amps) causing the fan relay to overheat and fail. If you replace the relay and it fails again chances are the fan itself needs to be replaced too, and a new fan may also be bad so check its resistance! Thejeepdoctor - too much resistance in the fan won't cause the fan relay to fail.
2004 Jeep Liberty Radiator
It's too little resistance that causes the failure.