P1781 4x4 Switch Out Of Range. Didn't know you had a 4 wheel drive, did you? Some aftermarket scanners produce erroneous codes. This could be what happened here.
Based on your symptoms, it sounds like you might have a charging system problem. Start by measuring battery voltage while the engine is running. All you need is an inexpensive digital voltmeter. You must find between 13.75 and 14.75 volts. If it is low the battery will not fully recharge while driving. Some simple additional tests will narrow down the cause. If it is within that range, remeasure it with as many electrical accessories turned on as possible or have your mechanic perform a load test on the alternator. Although rare on Chrysler products, if one of the six output diodes is shorted, you will only be able to get very close to one third of the alternator's rated capacity. That could mean less than 30 amps from a 90 amp unit. 30 amps is just barely enough to run the head lights / running lights, fuel pump, injectors and all of the computers leaving nothing left over to run the heater fan, radiator fan, radio, and recharge the battery. That means the battery will discharge as you drive.
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Saturday, April 16th, 2011 AT 11:59 PM