Keyless Remote

I have a 2004 Jeep Grand Cherokee and the keyless remote is not working very well

From the drives side of the car it will unlock / lock the doors if you are within one foot of the car

From the passengers side it will work from about 10 feet away it also seams better from the front than the rear

I have installed new batteries a couple of times in the remote and checked the voltage and they are ok

I have also tried different remotes

Can someone tell me if there is a sensor that can be cleaned and where it would be.