If an amp is desired for the Yukon XL and the original speakers are to be retained, a maximum of 200 watts should be used since the speakers are not likely to be capable of handling more. If higher performance or better quality speakers are desired, then the amp rating depends on the speakers.
To install an amp in a Yukon XL, the radio must be accessed first. Remove the lower dash covers on the driver's side. Remove the screws on the bottom side of the dash front reveal molding. Use a common screwdriver and carefully pop the front off the cover that covers the speedometer, radio and heater controls. Remove the cover by lowering the tilt steering column as far as possible and disconnecting all electrical connectors. Remove the screws holding the radio in, pull the radio out and disconnect the electrical connector and antennae. Look at the back of the radio and see if it has recesses for RCA plugs for speaker output for an amp.
Most amps only accept RCA plugs for speaker input. If there are no RCA receptacles, it is better to replace the radio with an after-market stereo with hook-ups for an amp, such as RCA jack recesses and a wire for a remote to turn the amp on and off. An amp uses RCA jacks for input from the radio and individual speaker connections for the output to the speakers. It also needs a separate power wire, a ground and a connection for a remote to turn the amp on and off.
If the stock radio had the RCA ports or a new radio is installed with these provisions, locate the amp where it can stay cool and unrestricted. Connect the RCA jacks to the radio and run the wires under the carpet to the amp. Connect the speaker wires to the amp speaker output and run them under the carpet to the radio. Split the wires for the speakers coming out of the radio and attach the new wires to the harness side of the radio harness going to the speakers. These can be denoted by four different pair of wires, one a solid color and one the same color with a black stripe. Use wire connectors to connect these.
Run a 16-gauge wire from the remote on the amp to the remote on the radio. Lastly run two 10-gauge wires from the amp through the firewall to the battery and attach them to the terminals in the right polarity. Install the radio and the retaining screws. Install the dash panel fascia.
