Where is this located on engine code P0400?

Question

Three codes came up. Would like to know where these are located on engine. Codes are P0400, P0325, P0170

Answer 1

P0400 Exhaust gas recirculation malfunction

P0325 Knock sensor circuit malfunction

P0170 Fuel trim lean Bank 1

When the fuel trim is lean this is a condition of the engine  where more air is taken in than fuel ratio. The fuel trim condition should be done first, this can be all related to just one cause, a lean condition will and does set a knock sensor code, Look for any vacuum hose that may have disconnected or ruptured.