My Service Engine Soon light is on. Truck has 150K, just tunes about 20K ago, truck starts and runs like a new one. Had code read and tech said it reads: "Catalyst Deficiency Below Threshold Bank 1". Now he told me 90% of the time this means an o2 sensor, but those sensors are NOT effecting the air fuel or the way the truck runs because they are down stream and are for polution.

Does this sound about right or anyone with a similar issue?

Kenny

 

Would that be P0420? You need a new cat, passenger side. That's "efficiency", not "deficiency". It's not the O2 sensor, it's fine, it's doing its job and reporting that the cat isn't up to snuff.

 

GLC,
Thanks for help. He didn't give a number for error code, his scanner just told what it was. I assume that if the CAT is bad after a while it may create backpressure? Funny thing like stated before the truck run like new, idles at 650 and smouth all the through the gears till cruising. What effects will this have on my truck?

Thanks Again,

Kenny

 

It depends if it's starting to clog or not. If not, you will never notice the difference except the CEL won't go off and you won't pass an emissions inspection. If it's starting to clog, the backpressure can cause problems.

 

He has a 650 rpm idle so somethings definitely wrong, that's about 100 rpm out.

A deficiency code would prove the sensor worthy, -so it not the O2. Faulty HO2S sensors do not produce the DTCs P0420 and P0430. The sensors must all be tested and shown to be reliable before the Catalyst Monitor can be called by the Executive. Bad Circuit or Sensor DTC's are usually 150 & 60 series DTC's.

With the idle being that low, I would think one of the 4 converters are plugging up. Make sure you don't have an exhaust leak. That could thro efficiency out as well.

 

My motor from new has always idled at that speed it couldn't be running smoother. Gonna have to get it reread and copy the exact code #. Also gonna check wires to HO2S, read about checking that too.
Thanks Guys.

 

No, 650 rpms is NOT the installed program, smooth has absolutely nothing to do with it lol.. Whatever- The program parameters are 720 - 750 rpms.

 

His tach could easily be off. They are not precision instruments...The scan tool should be able to read the engine speed accurately to see if the tach is accurate.

Cat efficiency codes can result from other faults, notably bad O2 sensors or mild misfires that dump excessive fuel into the cat causing it to degrade over time. Again, the scan tool can diagnose whether the cat is functioning. All the technician has to do is to watch the switch rates of the up and down stream O2 sensors and it will be obvious to a trained eye if the cat is working or not.