P0420 code after Protect and Restore

[rvsarch]

I received a notice from Acura soon after purchasing a 2011 Acura TSX Wagon, warning about oil consumption, extending the warranty and offering to replace the piston rings if oil consumption became excessive. They also suggested using only top tier gas and letting the car warm up before hard acceleration. Oil consumption has remained fairly constant at about 1 qt every 3k miles, so no warranty fix. I shortened OCI from the maintenance minder to 7,500 miles right away and then to 5,000. I did my last oil change using Valvoline 0w20 Protect and Restore for the first time and got a P0420 code for catalytic converter low system efficiency about a week later. I checked my oil and found that it had gone completely dark, so I drained it and put in 0w20 Kirkland. I suppose the “restore” part of the oil package loosened up a lot of carbon and I’m thinking it might have fouled the converter or sensors. I suppose the oil burning over 125,000 miles has not been good for them either. The car runs great and freeze frame at the time of the code shows a lambda of 1.009, short term fuel trim at 3.1%, and long term at -0.8 %.

I put in a bottle of Cataclean in a quarter tank of gas and drove 20 miles. Filled the tank and went on a trip of 100 miles at 70 to 80 mph, occasionally holding the transmission in 4th gear at about 3,600 rpm. No hesitation or drivability issues so converter is not clogged. Then I replaced upstream and downstream sensors with Denso, anticipating that I'd want new ones anyhow, in the event that I have to replace the catalytic converter. I cleaned the throttle plate and MAF sensor even though they looked pretty good. No evidence of exhaust or vacuum leaks and very smooth idle. I erased pending and confirmed codes, so CEL is off but permanent code is still there, because it's permanent. Fingers crossed.

 

[BMWTurboDzl]

I would have continued with the Valvoline product.

 

[ripcord]

I'd chalk it up to coincidence, not the oil. Could have been a lazy downstream O2 sensor.

 

[SC Maintenance]

I agree with your initial analysis. Hopefully the cataclean works for you.

2.4 or 3.5 in that? Would a thicker oil slow oil usage maybe?

 

[cptbarkey]

Your diagnosis and conclusions are lacking, but thank you for sharing the anecdote.

 

[rvsarch]

I would have continued with the Valvoline product.

Never had oil go so dark in a week and only about 50 miles, so I treated it like an engine flush.

 

[rvsarch]

Your diagnosis and conclusions are lacking, but thank you for sharing the anecdote.

Well, the P0420 code is generated by the downstream sensor readings in relation to the upstream sensor and other parameters in order to monitor the efficiency of the converter. My engine burns oil, so possibly a poisoned converter. I thought the protect and restore might have done some aggressive cleaning, since the oil turned so dark, so quickly. Maybe a coincidence. That's why I used a cleaner right after the CEL. Then I figured at 125k miles, it was not a bad idea to change the sensors in case they were fouled or just sluggish. They didn't look bad when I took them out, but Mass air flow rate at idle changed from bouncing between .05 and .04 to a steady .04 lb/min. Seems like short term fuel trim may have gotten a bit closer to zero, but hard to say. Just hoping CEL does not come back.

 

[rvsarch]

I agree with your initial analysis. Hopefully the cataclean works for you.

2.4 or 3.5 in that? Would a thicker oil slow oil usage maybe?

The 2.4 was the only engine choice for the wagon. A lot of opinions pro and con about using a thicker oil to combat consumption. I have also been reluctant to try an engine flush out of concern for the seals. I have zero leaks and colored concrete pavers where I park.

 

[John105]

Well, the P0420 code is generated by the downstream sensor readings in relation to the upstream sensor and other parameters in order to monitor the efficiency of the converter. My engine burns oil, so possibly a poisoned converter. I thought the protect and restore might have done some aggressive cleaning, since the oil turned so dark, so quickly. Maybe a coincidence. That's why I used a cleaner right after the CEL. Then I figured at 125k miles, it was not a bad idea to change the sensors in case they were fouled or just sluggish. They didn't look bad when I took them out, but Mass air flow rate at idle changed from bouncing between .05 and .04 to a steady .04 lb/min. Seems like short term fuel trim may have gotten a bit closer to zero, but hard to say. Just hoping CEL does not come back.

Here’s a question, and I know lots of people get that code and think CAT.

Is it cumulative? Meaning, at the time a P0420 is thrown, was the reading from that instant, or is a discrepancy building up and at a threshold, it’s thrown?

 

[SubieRubyRoo]

Well, the P0420 code is generated by the downstream sensor readings in relation to the upstream sensor and other parameters in order to monitor the efficiency of the converter. My engine burns oil, so possibly a poisoned converter. I thought the protect and restore might have done some aggressive cleaning, since the oil turned so dark, so quickly. Maybe a coincidence. That's why I used a cleaner right after the CEL. Then I figured at 125k miles, it was not a bad idea to change the sensors in case they were fouled or just sluggish. They didn't look bad when I took them out, but Mass air flow rate at idle changed from bouncing between .05 and .04 to a steady .04 lb/min. Seems like short term fuel trim may have gotten a bit closer to zero, but hard to say. Just hoping CEL does not come back.

Oil color doesn’t change from “cleaning” in 50 miles. It changes that quickly due to aminic antioxidants that are temperature-dependent.

 

[Drew7a]

Why would you use a 0w-20 in these known oil burners. These engines do great with 0w-40.

Look into a flush followed by HPL EC or Rislone for a few OCIs.

 

[SubieRubyRoo]

These engines do great with 0w-40.

Name an engine that doesn’t do great with 0w40. I’ll wait…

 

[SC Maintenance]

Here’s a question, and I know lots of people get that code and think CAT.

Is it cumulative? Meaning, at the time a P0420 is thrown, was the reading from that instant, or is a discrepancy building up and at a threshold, it’s thrown?

It takes multiple cycles to throw that code. It actually takes multiple cycles just to get a pending code so it’s usually not a one time event.

 

[burbguy82]

I received a notice from Acura soon after purchasing a 2011 Acura TSX Wagon, warning about oil consumption, extending the warranty and offering to replace the piston rings if oil consumption became excessive. They also suggested using only top tier gas and letting the car warm up before hard acceleration. Oil consumption has remained fairly constant at about 1 qt every 3k miles, so no warranty fix. I shortened OCI from the maintenance minder to 7,500 miles right away and then to 5,000. I did my last oil change using Valvoline 0w20 Protect and Restore for the first time and got a P0420 code for catalytic converter low system efficiency about a week later. I checked my oil and found that it had gone completely dark, so I drained it and put in 0w20 Kirkland. I suppose the “restore” part of the oil package loosened up a lot of carbon and I’m thinking it might have fouled the converter or sensors. I suppose the oil burning over 125,000 miles has not been good for them either. The car runs great and freeze frame at the time of the code shows a lambda of 1.009, short term fuel trim at 3.1%, and long term at -0.8 %.

I put in a bottle of Cataclean in a quarter tank of gas and drove 20 miles. Filled the tank and went on a trip of 100 miles at 70 to 80 mph, occasionally holding the transmission in 4th gear at about 3,600 rpm. No hesitation or drivability issues so converter is not clogged. Then I replaced upstream and downstream sensors with Denso, anticipating that I'd want new ones anyhow, in the event that I have to replace the catalytic converter. I cleaned the throttle plate and MAF sensor even though they looked pretty good. No evidence of exhaust or vacuum leaks and very smooth idle. I erased pending and confirmed codes, so CEL is off but permanent code is still there, because it's permanent. Fingers crossed.

View attachment 216208

I assume you have a 3L engine?
The scan looks good

 

[ripcord]

Name an engine that doesn’t do great with 0w40. I’ll wait…

Detroit Series 71

 

[Drew7a]

Name an engine that doesn’t do great with 0w40. I’ll wait…

That was the obligatory 0w-40 post, waiting for try HPL post.

 

[ctechbob]

I assume you have a 3L engine?
The scan looks good

2.4 K Series is all that ever came in the wagon TSX

 

[burbguy82]

2.4 K Series is all that ever came in the wagon TSX

well then the scan might not be good..............

the MAF sensor should be reading aprx, real close to engine displacement at idle, in grams per second......you scan shows 3, after the conversion to grams per second.

You might pull the sensor and clean it. Then recheck. If the MAF is reporting high it can cause calculation problems in fueling. Clean the sensor, and the connections.

 

[rvsarch]

well then the scan might not be good..............

the MAF sensor should be reading aprx, real close to engine displacement at idle, in grams per second......you scan shows 3, after the conversion to grams per second.

You might pull the sensor and clean it. Then recheck. If the MAF is reporting high it can cause calculation problems in fueling. Clean the sensor, and the connections.

That is after cleaning. I was wondering about the value being on the high side using rule of thumb. Does the upstream sensor compensate for this with fuel trim or does it end up running too rich?

 

[SC Maintenance]

That is after cleaning. I was wondering about the value being on the high side using rule of thumb. Does the upstream sensor compensate for this with fuel trim or does it end up running too rich?

You need to be looking at your long term fuel trim - not short term. Short term fuel trim is a meaningless number. Well it has some uses in high performance / high RPM but not here.

What is the LTFT at idle, and also while driving at constant speed under load, so steady speed at like 30mph?

My math gives me 3 grams / second which is quite high. The fuel trims would compensate for it but as you accelerate / decelerate there is a constant lag which means at anything other than constant speed its out of whack.