Help, does anyone know what these codes are? I have a 1998 Discovery, which has not had any problems until now, it failed emissions testing with the state. Any help anyone can give me would be greatly appreciated. Should I take this to the dealer or a local mechanic?

 

The P1316 - Excessive misfires detected possibley causing cataylst damage (excessive Emisions)

P1187 - Oxygen Sensor Heater Circuit Short Upstream

P1193 - HO2S Heater Circuit Inferred Open Circuit, Downstream Sensors