Try the paperclip jumping technique.
Passenger side: underneath the kickpanel at floor level, you will find your ecu, just above that there will be a blue plug hidden by a green sleeve. Pull it out of the sleeve. There are two wires leading to this plug, they pin into the plug, connect the two sides with a paperclip or piece of wire. Now turn the ignition on, the CEL will give you the codes. A long blink counts as the first slot.. short counts as the second slot
so for example, 5 long and 4 short blinks = 54. The codes will be seperated by a long pause. Try this first, before you go replacing parts that dont need it.