Just got a CEL today on the way home and when I pulled the code it was a P0420. I've read this could be due to switching the sensors by mistake (front to rear). I checked twice but I'll look again tomorrow. Could this have anything to do with my new exhaust (200 cell cats)? No sure if a cat inefficiency code is different but I can't see that happening with the 200 cell cats. Any advice appreciated. Thanks

 

That code is : Catalyst System Low Efficiency......So yes it could have to do with the new cats , it would be an issue if the banks are in reverse order

 

Do the banks have to be reversed to get this code?

 

I've read its not from getting the banks switched (not sure if thats even possible as the wires aren't long enough to go to the wrong side of the car), but from switching the primary o2 sensor for the after-cat sensor.

 

My question was wheather you can get that fault code without having the O2 sensors hooked up incorrectly.

 

here is the info i found

 

Thanks for the info Colorinc!
Looks like a need a dataloger to eval the code. I get it very intermittantly after installing sport exhaust with 200 cell cats. I have cleared it twice but it continues to come on every week or so. I suspect if O2 sensors reversed the code would be constant? Maybe an O2 sensor is getting weak (aged)? I doubt its the valve lift problem since it is temporally related to the sport exhaust installation...

 

MBailey, yes that is my question also, is this possibly related to cat inefficiency (ie high flow cats that don't clear up as much emissions as the stock units). It sounds like your problem is very similar to mine if you keep getting the code and the sensors aren't switched. You can actually just stick your head under the rear of the car and see if the sensor with the grey sleeve is in the front or rear position. I think its actually due to the aftermarket cats though. Most people probably don't notice though as they have a tune to go along with their exhaust that may eliminate the CEL.

 

check your wires look for cracks or a small short also corrosion where they plug into the harness thats what i ran into

hope this helps

tim