CEL Question?

[4ever4d]

First off Merry Christmas everyone,now to the problem couple days ago on my way home cel comes on go to my brother in law ,has a body/auto repair shop yea i am lucky does most my stuff for parts cost+lunch,scans my x a 97 4x,4.0 sohc comes back"right bank catalyst above threshold" after conversing about it, my x needs plug change, he suggest change plugs and injector cleaner may clear up problem if not cat converter or o2 sensor behind cat could need replacement i dont want to randomly change parts gets expensive, so what you think most likely cat or o2 sensor any help will be appreciated !

 

[2000StreetRod]

P0420?

Was the DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)? I'm not aware of a code for efficiency above threshold.

How many miles do you have on the odometer? The catalytic converters frequently last more than 200,000 miles if the engine is maintained in proper tune.

If you're not getting any mixture related codes (bank too rich) then it could be your rear O2 sensor. If you want to be sure, you could swap sensors between banks and see if the DTC changes banks. That might be a lot of work depending upon the sensor location and accessibility.

Make sure that you don't have any of the following:
P0136 02 Sensor Circuit Malfunction (Bank I Sensor 2)
P0137 02 Sensor Circuit Low Voltage (Bank I Sensor 2)
P0138 02 Sensor Circuit High Voltage (Bank I Sensor 2)

 

[4ever4d]

Yes you are correct my bad, brain fart below was what i should have said!

 

[4ever4d]

Yes you are correct my bad, brain fart, below was what i should have said, have 176k miles, no other codes,he is leaning toward o2 sensor problem,he has mitchell and alldata loaded on his computer they brought up possibility of cat problem, thanks for the info!