Make sure there are no items, especially metallic, stored on the dash board and at the base of the windshield on the drivers side. This could interfere with the remote transmitter signal to the wireless control module.
Since these vehicles are only 2 years apart in age the remote transmitters should be the same style. Swap the batteries between the 2 transmitters. If the good battery from the 2002 vehicle fob is placed in the fob transmitters for the 2004 vehicle and the 2004 vehicle now will have its doors unlock from a distance of 25 - 30 feet, then you know the problem is attributable to a weak battery. If you have a volt-ohm meter you can check the voltage of the battery and it should be close to 3.0 volts. If less then the battery life is suspect. Also make sure there is no corrosion on the battery positive and negative poles and the battery contacts inside the remote transmitter. Any corrosion will lessen voltage and signal. strength.
If the battery swap does not fix the problem then there is a transmitter problem but I suspect you have a weak battery in the transmitter.
I looked at a service manual for a 2003 Neon (which should be similar) and it indicates the transmitter fob uses two Panasonic CR2016 or equivalent coin style batteries. Service manual indicates battery life to be in the range of 1 - 2 years. Battery life is certainly variable in all types of applications.
Since these vehicles are only 2 years apart in age the remote transmitters should be the same style. Swap the batteries between the 2 transmitters. If the good battery from the 2002 vehicle fob is placed in the fob transmitters for the 2004 vehicle and the 2004 vehicle now will have its doors unlock from a distance of 25 - 30 feet, then you know the problem is attributable to a weak battery. If you have a volt-ohm meter you can check the voltage of the battery and it should be close to 3.0 volts. If less then the battery life is suspect. Also make sure there is no corrosion on the battery positive and negative poles and the battery contacts inside the remote transmitter. Any corrosion will lessen voltage and signal. strength.
If the battery swap does not fix the problem then there is a transmitter problem but I suspect you have a weak battery in the transmitter.
I looked at a service manual for a 2003 Neon (which should be similar) and it indicates the transmitter fob uses two Panasonic CR2016 or equivalent coin style batteries. Service manual indicates battery life to be in the range of 1 - 2 years. Battery life is certainly variable in all types of applications.