Intermittent P0420 code

[Vindictus]

This started Monday night. Out to the store and CEL came on. I rest it, went to work Tuesday (60 miles) all was good. Went out after work it came on again. reset it and came on, on my way home to night. I replaced both cat's and O2 censors about 3 years ago. O2's are motorcraft cat's are from Eastern Catalytic. Shouldn't they last longer?? Could anything else besides a bad cat cause this? Like an exhaust leak of some kind? Thanks everyone

 

[DILLARD000]

OBD2 TroubleCode p0420 = Catalyst Efficiency Below Threshold Bank1\RightSide
Either a bad CatCon or OxSensor? I'd try cheaper option of a new OxSensor first.

 

[Craig0320]

Check your rear o2 sensors on a scanner and they should be mostly solid non moving if you have a good functioning set of cats. In park at operating temperature have the engine at a constant 2000 rpms. Using a digital thermometer take the inlet cat temp and the exit cat temp. The temperature should be hotter coming out the back by at least 200 degrees even a little less won't through a code. This lets you know the cat is doing what it's supposed too.

 

[Vindictus]

Check your rear o2 sensors on a scanner and they should be mostly solid non moving if you have a good functioning set of cats. In park at operating temperature have the engine at a constant 2000 rpms. Using a digital thermometer take the inlet cat temp and the exit cat temp. The temperature should be hotter coming out the back by at least 200 degrees even a little less won't through a code. This lets you know the cat is doing what it's supposed too.

I did check them with my scanner and they are not moving very much. My scanner is showing both cat's almost identical temp's. I'll bring a temp gun home from work and check this weekend. Thanks for the help

 

[Vindictus]

OBD2 TroubleCode p0420 = Catalyst Efficiency Below Threshold Bank1\RightSide
Either a bad CatCon or OxSensor? I'd try cheaper option of a new OxSensor first.

i ordered new O2's the cats still have warranty. Thanks

 

[Vindictus]

I had a chance to look at this p0420 code some more. Code reader list these as possible causes.
Incorrect fuel grade used
fault Bank 1 Sensor 1 Oxygen sensor
Fault Bank 1 Sensor 2 Oxygen sensor
Faulty Engine Coolant Temperature (ECT) sensor
Damaged or Leaking exhaust system
Excessively retarded spark timing

Why can't it be easy

 

[Vindictus]

Changed O2 sensors and CEL still throws 420 code. I will check inlet and outlet temps of cat when i get to work in the morning

 

[Vindictus]

Check your rear o2 sensors on a scanner and they should be mostly solid non moving if you have a good functioning set of cats. In park at operating temperature have the engine at a constant 2000 rpms. Using a digital thermometer take the inlet cat temp and the exit cat temp. The temperature should be hotter coming out the back by at least 200 degrees even a little less won't through a code. This lets you know the cat is doing what it's supposed too.

I checked my cat's temp's this morning. The inlet temp is 445F the outlet temp is 285F with a difference of 160F so looks like I need a new cat I wonder if it's worth doing warranty through rockauto?

 

[Craig0320]

I would reach out to them first. That is definitely not doing it's job effectively.

 

[19Walt93]

First, the "rear O2", isn't an oxygen sensor, it's called a cat monitor. Ask an experienced Ford counterman for a rear O2 and he'll look at you like you're an idiot. I agree with trying the cheap stuff first but I have never seen a PO420 fixed by replacing anything but a cat. We replaced darn few, almost exclusively with OEM parts or Walker direct fit cats if the customer gasped at the OEM price.