5.0Edition

The code says Catalyst system efficiency below threshold (Bank 1). Is that the o2 sensor before or after the cats. I don't understand why it came on. I have the Slp x-pipe with cats.

tbirdscwd

Thats because your catted x from SLP doesn't clean up the exhaust as well as the stock 4 cats did. Most of the time they will work well enough to keep your MILs from throwing a code, but not always. Do you have a tuner? If so, just turn off your MILs. If not, you will need MIL eliminators to get rid of the CEL.