OBD-2 Code Definition

[Ranger379]

hey guys, i got a CEL the other day and hasnt went off. i bought a cheap scan tool at walmart (one i bought and returned while ago cause it didnt work on my moms 95 lol) anyway i got the code P0420. cleared it and here i am now. i looked in the book to find this: P0420 Catalyst System Efficiency Below Threshold (Bank 1). what does this mean? i have been looking for a while and can just find that. what would be wrong?
thanks for the help.

 

[dogfriend]

 

[dogfriend]

In English, it means that the PCM is comparing the reading from the O2 sensor before the Cat and the O2 sensor after the cat and based on the readings has decided that the Cat is no longer working.

 

[Ranger379]

so its my cats? i just reaplaced the exhaust with catback gibson. exhuast was horrible. the cats wherent that great looking either lol nothing to worry about then? could it be a bad 02 sensor? thanks for the reply

 

[ExplorerDMB]

It would be best to look at the live data stream from your vehicle, but since you don't havethe resources, it's pretty safe to say that your 02 sensor is working. Like stated above, you probably need a cat (s)

-Drew

 

[Ranger379]

lol wouldnt be ther cheaper of the two with my luck. i was hoping it was 02 sensors cause cats are pretty expensive lol. well i guess they will stay the way they are till i get more money lol. thanks everyone for your help

 

[paroxysm419]

i just replaced both of my o2 sensors because i was getting a code for them, and now that catalyst test won't reset. the o2 test and the o2 heater test ran, and didn't give me codes, but for some reason the catalyst test won't reset. any ideas why that would be?

 

[dogfriend]

i just replaced both of my o2 sensors because i was getting a code for them, and now that catalyst test won't reset. the o2 test and the o2 heater test ran, and didn't give me codes, but for some reason the catalyst test won't reset. any ideas why that would be?

IIRC, you must complete a certain number of drive cycles before the "ready" status is set. So, you might just need to drive more.