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My Journey to solve the P0420 error - NOT RESOLVED!
My wife's IS350 (175K miles) has been throwing the dreaded P0420 trouble code (Catalyst System Efficiency Below Threshold (Bank 1)) for a few weeks now.
To date, I've done the following: - Replaced the 1st o2 sensor (under the battery inside the engine bay)
- Tried the Scotty Kilmer lacquer thinner cleaning trick:
- Checked the exhaust piping near the y-pipe, just after the heat shields
Code still exists. I inspected all my exhaust piping looking for some of the wear that I've seen people posting here, but the exhaust looks to still be in good shape. See pics below.
In order to diagnose this properly you need to compare the AF reading to the O2 reading on each bank. First, make sure that the AF and the O2 are operating within the appropriate ranges by performing an active test to force the mixture +25% and -25%. Once the sensors are confirmed to be operating as designed you can compare the readings. Post-cat oxygen levels should be much lower than pre-cat. Therefore, you should see much less of a change in oxygen content past the cat if it's doing it's job. If the AF and O2 are "dancing" together you are guaranteed to have a bad catalytic converter.
In order to diagnose this properly you need to compare the AF reading to the O2 reading on each bank. First, make sure that the AF and the O2 are operating within the appropriate ranges by performing an active test to force the mixture +25% and -25%. Once the sensors are confirmed to be operating as designed you can compare the readings. Post-cat oxygen levels should be much lower than pre-cat. Therefore, you should see much less of a change in oxygen content past the cat if it's doing it's job. If the AF and O2 are "dancing" together you are guaranteed to have a bad catalytic converter.
Not to thread jack, but this is for leoferus.
Denso Spark Plugs #3473 I have installed were pregapped at .038" VS OEM Gap is at .043". Since I was having a coil pack issues. I decided to get new coil packs, and it solved my problem. Since people say the plugs come pregapped. I then checked the new ones I ordered, and they also checked at .038". I've now corrected the gap on Bank 1 to .043". This weekend I plan to open up bank 2 to install new coils, and plugs. So that everything starts off fresh from 80k. My old plugs already have 30k on them as of now.
So my question is will a gap of .005" make a difference?
Denso Spark Plugs #3473 I have installed were pregapped at .038" VS OEM Gap is at .043". Since I was having a coil pack issues. I decided to get new coil packs, and it solved my problem. Since people say the plugs come pregapped. I then checked the new ones I ordered, and they also checked at .038". I've now corrected the gap on Bank 1. This weekend I plan to open up bank 2 to re gap the plugs.
So my question is will a gap of .005" make a difference?
You just taught me something! I replaced mine about 10k ago. There's no evidence that they had an impact on performance. That's not exactly proof and I'll probably gap them next time I replace them but I won't be pulling them just to gap them.
That's good to know, I used the Denso IKBH20TT plugs which are .04 gapped and on the forums they said a .002 gap will not make a difference. I guess somewhere between .002 and .005 it starts mattering.
Even if your FT was out of wack if your cat is healthy it will eat oxygen. Therefore, if there are ten oxygen molecules at the AF there should be x less at the O2. So, the ECM would see 10-x when rich and 7-x when lean... you get the point. In my experience with Toyotas, that is. Besides, if your FTs are jacked you'd set codes for them. In Toyota products P0420 is almost always a sensor failure, a cat failure, or a ECM.
In Toyota products P0420 is almost always a sensor failure, a cat failure, or a ECM.
I have to disagree, at least with this car. In the vast majority of cases with the 2IS (mine, my former colleague with an IS350, dozens of people on this forum, etc.), the P0420 (and/or P0430) is caused by an exhaust leak, usually at the Y-pipe under the heat shield. The OBD2 cat efficiency test is run just as the car warms up after a cold start. An exhaust leak bleeds hot exhaust gasses such that it takes longer for the cats to get hot enough to light off. If they haven't lit off by the time the cat efficiency diagnostic runs, you get the P0420/P0430 code.
I have to disagree, at least with this car. In the vast majority of cases with the 2IS (mine, my former colleague with an IS350, dozens of people on this forum, etc.), the P0420 (and/or P0430) is caused by an exhaust leak, usually at the Y-pipe under the heat shield. The OBD2 cat efficiency test is run just as the car warms up after a cold start. An exhaust leak bleeds hot exhaust gasses such that it takes longer for the cats to get hot enough to light off. If they haven't lit off by the time the cat efficiency diagnostic runs, you get the P0420/P0430 code.
You're quite right. I overlooked that fact. A leak would certainly be able to cause this condition. Smoke test.
So, connected my OBD2 reader to pull the O2 information. I've attached it here. What I find interesting is that SHRTFTB1S2 shows "N/A."
Also, under engine load (2500 to 3000 RPM drive on the highway), I noticed that the B1S2 O2 sensor was always running at a higher voltage when compared to bank 2 (which has been problem-free), but the voltage always stayed between 0.35 and 0.8 Volts.
10-07-18, 08:15 PM
My Journey to solve the P0420 error - NOT RESOLVED!
