Uart module 4 doesn't produce a signal

Hello,

I am trying to use UART4 for one of my applications, but can't make it work. 

I don't receive any data trough the terminal. Scoping the signal I notice that the TX pin level is constant high.

Here is my code:

#include <stdint.h>
#include <stdbool.h>
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"
#include "driverlib/gpio.c"
#include "driverlib/pin_map.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "inc/hw_gpio.h"
#include "utils/uartstdio.c"
#include "driverlib/uart.c"

void UartSetup(void);

int main ()
{
	int i;
	SysCtlClockSet(SYSCTL_SYSDIV_5| SYSCTL_USE_PLL | SYSCTL_OSC_INT | SYSCTL_XTAL_16MHZ);
	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);

	UartSetup();

	while(1)
	{
		for (i = 0; i < 1000; i++)
		{
			UARTprintf("\rHello Riko %d!", i);
			SysCtlDelay(40000);
		}
	}
}

void UartSetup(void)
{
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);
    SysCtlDelay(3);

    GPIOPinConfigure(GPIO_PC4_U4RX);
    GPIOPinConfigure(GPIO_PC5_U4TX);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_UART4);
    SysCtlDelay(3);

    GPIOPinTypeUART(GPIO_PORTC_BASE, GPIO_PIN_4 | GPIO_PIN_5);
    UARTClockSourceSet(UART4_BASE, UART_CLOCK_PIOSC);
    UARTStdioConfig(4, 9600, 16000000);
}

It compiles but I don't get the output. I tried with UART0 and it worked just fine, but with UART4 don't have same outcome.

Please help. Thank you!