bad remote signal from toyota corrola

I installed an alarm system in to my friends toyota corrola 1997 model,the alarm system has very bad signal in this car.I have the same system in my car and it works quite fine.okay,I have switch modules.plucked mine into his loom and his into my loom.his module works 100% in my car with wide range.my systems signal is bad in his car.this is what I tried.moved the module all over under the dash (all over),made sure its not against thick bare metal,exteded the antenna wire,removed it from the loom and wired a chassis and 12 wire from engine bay to the inside of the car incase there was something wrong with the loom wiring.but stil the same.it only get signal when you stand next to the car.but if you stick the module outside the car it works 100%.that's where I discovered that there's nothing wrong with the system.what can it be interupting the signal of this module.first time something like this is happening.Mr signal

Try changing the remote.

I did that already,I took that module out of his car and plucked it into my car and the remotes work quite fine in my car.Mr signal

Bad unit, needs swapping.

did that aswell,swapped the units with a new one,the new one also doesn't get signal from his car.Mr signal