well a couple weeks ago i get off work and proceed to start my car. As soon as i turn the ignition on it starts then stumbles, backfires and dies. it seems to be doing this more and more lately. I used my hand held tuner and got trouble codes "P0420- cat system efficiency below threshold." i have an offroad pipe on it.
"P0340- Cam position sensor A circuit (Bank 1 or single sensor)

ok now the first one i kinda understand but the second one has left me completly baffled. any help would be greatly appreciated.

its an 03 mustang gt 5 speed with 70,xxx miles

 

you have an issue with the right side cam sensor or wiring. check the connections and wiring for damage

 

ah ok, thanks for the help. ill go and check now.

edit--
cant seem to find any frayed or loose wires. ill get it up on my friends lift tonight and see if i can find anything. thanks again for the help

 

i was just looking at the pinpoint for this code, locate the suspect sensor( right bank of engine) unplug connector and measure the resistance of the sensor. it needs to be between 250-1000 ohms. if not replace sensor. if that passes the test its a wiring issue and gets more complex to diag. good luck