you have too much of a load on your radios outputs (this could be ohm load or one channel is shorted out),my first question is;did you replace front speakers, and did you have concert sound(total of 4 speakers up front?)if you did ,aftermarket speakers are 4 ohm (which are louder BUT is more of a load)the lower the ohm rating,the more of a load on the radio it is.factory speakers are 10 ohm,so radio saw 5 ohm(dashand door speaker) per left and right sides, this would make aftermarkets speakers show 2 ohm (only high current amps can handle this kind of load )if this is the case,take it to a stereo shop and have them wire left speakers in SERIES and right as well.this will put ohm load in acceptable range(should then show 8 ohm per set)
if not heres a simple test to see what channel(s) are shorting out;
use your fader/balance controls and play one channel at a time( ie;fade all the way to front and also balance all the way to left)then turn up volume(this should be only speaker working )now and see if it cuts out like before..do this for all 4 channels and make notes of which speakers(s)had this problem...this will tell you which speaker to pull out and double check the wiring and make sure wiring is not touching each other or body(ground)if no shorts found try another speaker in its place to see how it plays.....if you do have a multi meter check ohms on each channel(at the radio,this test wiring too),you dont want anything LOWER than 4 ohms....
if i striked out here take to a stereo shop and have every thing checked....