UART4 configuration

Hi
Has anybody had problem with configuring UART4 of STM32L162VD?
I initialized USART1,USART2,USART3 and UART5 but not able to do for UART4!
I checked it with second board to make sure no hardware problem. Is it possible to debug UART 4 and 5 in Keil?

below is my code:

void uart4_configuration(void)
{
        USART_InitTypeDef USART_InitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4,ENABLE);

  GPIO_PinAFConfig(GPIOC, GPIO_PinSource10|GPIO_PinSource11, GPIO_AF_UART4);

  /* Configure UART4 pins:  Rx and Tx ----------------------------*/
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_10|GPIO_Pin_11;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(GPIOC, &GPIO_InitStructure);

  USART_InitStructure.USART_BaudRate = 9600;
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;
  USART_InitStructure.USART_StopBits = USART_StopBits_1;
  USART_InitStructure.USART_Parity = USART_Parity_No;
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
  USART_Init(UART4, &USART_InitStructure);

  USART_Cmd(UART4,ENABLE);
//        /* Enable RXNE interrupt */
  USART_ITConfig(UART4, USART_IT_RXNE, ENABLE);
//    /* Enable USART1 global interrupt */
  NVIC_EnableIRQ(UART4_IRQn);
}