I have a 2009 gmc sierra, where is the wiper relay location.

The PCB wiper relays are soldered directly to circuit board inside the under hood fuse box.
The windshield wiper/washer switch signal circuits are inputs to the body control module (BCM) and the BCM controls wiper motor low speed operation, washer pump and high speed operation. The windshield wiper/washer switch is provided a low reference from the BCM and each of the switch signal circuits is supplied 12 volts through a resistor and monitored within the BCM. During LOW or INTERMITTENT operation the wiper switch low signal circuit is closed to the low reference circuit through a series of resistors within the switch assembly and the signal circuit voltage monitored by the BCM will depend on the switch contact location to the resistor assembly. During HIGH or WASH operation the high and wash switch signal circuits are closed directly to the low reference circuit within the switch assembly and nearly all the signal circuit voltage will be dropped across the BCM resistors. The BCM controls the wiper motor through the WIPER CONTROL PCB Relay and the WIPER SPEED PCB Relay. During any wiper motor function that uses low speed the BCM supplies the voltage to energize the WIPER CONTROL PCB Relay and battery voltage will be supplied from the WIPER CONTROL PCB Relay through the de-energized WIPER SPEED PCB Relay to the wiper motor low speed control circuit. During high speed wiper motor operation the WIPER CONTROL PCB Relay is energized as in low speed and the BCM provides a ground to energize the WIPER SPEED PCB Relay and the battery voltage is supplied to the wiper motor high speed control circuit. Wiper motor park operation is controlled by the BCM using an input from the park switch within the wiper motor assembly. The BCM supplies the park switch signal circuit 12 volts through a resistor then monitors the circuit. Whenever the wiper motor is out of the park position the park switch signal circuit is closed to ground and nearly all the signal circuit voltage will be dropped across the BCM resistor. When the wiper switch is turned to the OFF position while the wiper motor is somewhere in mid-cycle, the BCM will continue to operate the motor until the wipers reach the park position. If the ignition is turned OFF while the wipers are in mid-cycle, the wipers will stop immediately where they are and the BCM will park the wipers the next time the ignition is cycled ON.

DTC B3715 02: Front Wiper Relay Drive Circuit Short to Ground
DTC B3875 00: Wiper High Speed Relay Circuit
DTC B3922 00: Front Wiper Function Select Circuit
Have it checked for DTC'S - diagnostic trouble codes .

The body control module (BCM) controls the wiper motor based on input from the windshield wiper washer switch. The BCM monitors the wiper washer switch through three separate signal circuits and a ground circuit. The windshield wiper switch high signal circuit is used to determine high speed wiper operation, the windshield wiper switch low signal is used to determine low speed, intermittent, and mist operation through the use of a resistor ladder, and windshield washer switch signal circuit is used to determine washer operation.
The BCM controls the windshield wiper motor through two output controls, controlling two relays which determine the desired wiper speed, high or low.
Your best bet , take your vehicle to a qualified repair shop or dealer . Hooking up a factory scan tool to see what the wiper switch inputs to the BCM are correct and outputs to relays are good .