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Discussion Starter #1
1996 Toyota Camry LE, 4 door sedan, auto, 5S-FE (4 cylinder)

Problem
Check Engine Light (CEL) is on. P0420 code. Currently, Camry runs fine and gas mileage is okay so still driving car daily with CEL on. Unfortunately, this is not the first time to work on emission system.

Background
March, 2012 @ mileage 161654 – P0420 problem – so I installed new Magnaflow 50801 cat along with both upstream and downstream Denso oxygen sensors from RockAuto. Problem fixed.

August 2014 @ mileage 177540 CEL is on again (I don’t have DTC from this repair). Local automotive shop installs new EGR vacuum switching (control?) valve. Problem fixed. (I was not available to work on car at this time.)

October 2014 @ mileage 178250 CEL is on again - P0303. No 3 fuel injector failed. I replaced all injectors with re-manufactured injectors from RockAuto.

(Currently) October 2017 @ mileage 198114. It is a little over 5 years and 36450 miles since last cat and oxygen sensors installed and P0420 code is back. Only P0420 code is present – no other codes retrieved.

Camry is driven by elderly women daily on short, low speed, in-town trips (10 miles or less), which I already understand contributes to dirty engine problem. Car is run on regular (cheap) gas. Camry is regularly maintained by me since 2012. I change plugs, synthetic oil and filter, air filter on a regular basis (five thousand mile mark). Camry was not truly well maintained prior to 2012.

I guess the above failed components are not necessarily unusual given that the Camry is driven daily on lots of short, in-town trips. That’s been the driving environment of the car since new.

I’m reading about emission systems to hopefully get smarter on this topic. I recently bought Innova 3140d scanner but not well versed on using it yet, so reading more about what I can detect with this scanner.

Questions for Fellow Forum Members
(1) Does replacing cat for second time at almost 200K seem unusual?
(2) Since I’m retrieving only P0420 code, I’m not aware of any other issues with engine. Car starts and runs fine. I’m thinking about cleaning/replacing idle air control valve, which has never been done. What should I be looking for or doing at this point given above repair history?
(3) Did I create problem buying Magnaflow catalytic converter instead of OEM cat in 2012?
(4) What don’t I know?


Haven’t bought any new repair parts just yet. Hope to hear from wiser forum members first. Any guidance is greatly appreciated.
 

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It's either the aftermarket CAT was cheaply made or something made it to go bad again. The fact that the original CAT went bad something had to make it go bad so first find the reason. Did you check the fuel trims? Does it run lean or rich? Most common reason to kill the CAT.

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1995 Camry LE Wagon
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Short trips may not allow CAT to heat up enough to burn off rich burn on cold start - engine may not even go into closed loop. Not sure if that year has heated O2 sensors.

If you have a laser temperature probe you can test the temp of the CAT on full warm up. If it's not getting to full operational temp that could be your problem.

I think there is a YouTube vid on flushing the CAT with solvent, maybe look at that - but no recommendation from me. You can also pull the O2s to check their condition.
 

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At this point, I would try the Lacquer Thinner trick. At one gallon of lacquer thinner to 10 gallons of gasoline and take a 200 miles highway trip to clear up the CAT. Scotty killer swears by it and it won't heart anything but my fix your problem if the fuel trims are in range. Find his YouTube video, that explains the procedure

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1994 Camry V6 XLE-J
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agree...use oem cat, especially if you need to pass emissions, and drive it on a trip every now and then, plus run some techron and/or cataclean through it to clean stuff up a bit.
don't understand about the IAC valve. it does need to be cleaned as part of routine maintenance but it won't cause this code. also the egr valve, modulator, temp sensor if equipped, and egr vsv need to be cleaned/inspected/replaced as necessary if not within haynes/fsm specs, along with associated vacuum hoses for the egr system and other hoses as well.
shoot us the short and long term fuel trims at closed loop idle and 1500 rpm, along with maf g/s to see if you have a driveability problem. if you got a cel now, also post the freeze frame data. note that unless all 6 monitors are 'ready', you won't have a complete picture of the health of the system.
tony
 

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Discussion Starter #6 (Edited)
Okay, now I have marching orders. That's what I was looking for. Thanks much to everyone.

Will gather data as requested. Haven't done any of this before; am in process of learning how to use new scanner. Will probably take several days to get organized and report back. Don't have laser temp probe, but not opposed to buying one if it ultimately helps correctly diagnose problem. I know enough to know that "upstream" problems often kill the cat, so all the comments about various readings (check this, check that) and inspection of emission components are helpful to me. (That's basically why I am posting and asking questions instead of just immediately replacing the cat again.)

Regarding idle air control valve . . . agreed, not primary source of P0420 code . . . its just that it might be a small contributor to dirty engine problem, along with how car is driven (short frequent trips). That's why I mentioned it.

Tony, not sure what this phrase means:
"unless all 6 monitors are 'ready . . ." Please note that I am currently reading user manual about new scanner, so I guess I will know shortly what you reference or may have to ask you to explain. And yes, CEL is currently on - but you wouldn't know it by how the car runs (car starts and runs great).

For now, will not go the lacquer thinner route until I have exhausted all other inspection and data gathering steps mentioned. Will report back as soon as I can.

All check this, check that comments are most helpful at this point.

 

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Discussion Starter #7
Scanner data as requested. No MAF data available, either car or scanner doesn't provide, or I don't know what I am doing yet. Haven't had time to research MAF data; posting what is immediately available. Still in learning mode about scanner and emission systems.


Live data - idle (755 RPM): STFT B1(%) = -0.8 LTFT B1(%) = 5.5
Live data - 1593 RPM: STFT B1(%) = -2.3 LTFT B1(%) = 1.6

Freeze frame data for P0420 DTC is attached.
 

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Everything looks fine to me. If lacquer thinner doesn't work, you have a degraded cat. Can try installing a sensor spacer on the downstream sensor which will eliminate the code. Of course, you do this at your own risk and accept all liability...it won't pass visual at smog time if they know what they're looking for.
 

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The fuel trims are very good so next I would just make sure that the CAT is clogged before you try the LT. For this you need a $30 laser heat gun from Amazon. While the car is in closed loop or up to a normal operational temperature get down and point the laser heat sensing gun at the exhaust pipe near the CAT. Measure the temperature before the CAT and after the CAT. The results should be very close. If the CAT is clogged the temperature before the CAT will be much hotter than after the CAT. You can also go to any repair shop and have them measure the pressure in the same spots by drilling holes before and after the CAT. If the pressure before the CAT is much higher from the after the CAT this will be the definite diagnosis of clogged CAT.
 

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1994 Camry V6 XLE-J
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+1 on isb's assessment of your freezeframe data. looks great for 200k miles. seems a bad cat would give higher long term trims. If a vacuum gauge hooked to manifold vacuum doesn’t hold idle vacuum when rpm’s are increased to 2500 (aka the pressure drops lower or to zero as the rpm’s increase), then you have a clogged cat or other exhaust restriction such as pinched pipe, etc.

if you eliminate the cat as a problem, then you might have a defective up or downstream o2 sensor that's giving the ecu bad input info, causing the ecu to throw an errant cat code. have you replaced any of the sensors? if so, which one(s) and at what mileage.
tony
 

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Discussion Starter #11 (Edited)
First, appreciate all the valuable input.

Glad to know nothing bad showed up in scanner results so far.

It’s time I upped my repair game. Will need to purchase infrared temp gun and vacuum tool to perform diagnostic tests as recommended. So, will need more time to order tools and perform tests.

Both O2 sensors were replaced in March 2012 @ 165K miles, which was 36450 miles ago when I installed Magnaflow cat (currently on car). Bought new Denso sensors at that time.

For now, will pass on lacquer thinner and sensor spacer option. Don’t have to pass emissions test until March of next year, so have this fall to diagnose and fix things correctly.

I definitely want to inspect-test EGR components and vacuum hoses per mcgowaw’s earlier suggestion (even though I don’t yet have indication anything is bad except the cat).

I think new scanner provides data about O2 sensors directly, but I need to learn how to run test and read results. So, will work on that.

Will report back results as I get them.

One last general maintenance question for now. . . . Does it make sense to rip-and-replace all/most vacuum hoses on Camry nearing 200K mileage/21 year age mark? We still want to drive our "old" Camry without problems for a few more years.




 

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re: replacing all vacuum hoses. you could for sure. however, if the current ones are still supple and not hard, then you could also just snip the ends and reconnect after verifying there's no holes/slits in them. don't forget to check the accordian creases in the intake snorkle for cracks too while you're at it. the pcv and other components cause also cause vacuum leaks if that's what you're worried about but so far we've seen no signs you have any.

note that the 420 code will trip when the cat goes below about 90 percent efficiency so it's probably your cat won't fail either the temp or the manifold pressure testing described above.

if that's the case and you need to pass emissions, run a couple of bottles of autozone's cataclean through an almost empty tank per bottle instructions and then drive until the 6 systems are 'ready' and you should be good to go.
tony
 

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Discussion Starter #14
Tony: What I basically understand is that scan results so far don’t indicate much wrong other than cat failure/partial failure – and that cataclean or equivalent might clear up problem for awhile. If it is as you suggest, a marginal problem, then additional testing may not reveal much. Appreciate that insight.

Regardless, I’m going to buy additional diagnostic tools and teach myself some new tricks. If nothing else, I hope to confirm that nothing unusual is going on with Camry.

Stillrunning: posted video seems spot on, thanks. Just bought Haynes Techbook OBDII manual. So, will read and hope to teach myself more about emission systems soon.

Will post back to this thread after further testing completed.
 

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Discussion Starter #15 (Edited)
NOV 2018 UPDATE - Problem remains

Nov 2018, Update to thread: Temporary P0420 DTC remains. Ran various tests and sharing results below.

Recent Tests and Visual Observations
Mileage: 206K, car driven about 8K annually.
CEL Status: Last time I posted, CEL was on - P0420 DTC. Now CEL is off, again.
Dry Compression Test: Cyl 1 = 232 PSI, Cyl 2-4 = 230 PSI. Turned engine over about 10-12 times (5-6 seconds). Ran tests twice with virtually identical results. Compression seems too high.
Vacuum Test: idle (~750 rpm) – 21 in Hg with steady needle, 1500 & 2500 rpm – 22 in steady. No indication of any major problem.
Hard Acceleration Vacuum Test: Under hard acceleration, vacuum drops to about zero, swings back to ~25 in, and then almost immediately settles back to 21/22 in Hg at idle. No exhaust restriction problem.
Spark Plugs: Visual observation, plugs look okay.
Catalytic Converter Heat Test: Inflow (top) = ~425-450 Fahrenheit. Outflow (bottom) = ~300-325 Fahrenheit. So, about 100-125 degree difference. Not good. Maybe StillRunning is right, maybe CAT is not getting hot enough. I thought CAT should be closer to 600 degrees operating temp, don't know if 450 degrees is within range (at idle sitting in driveway).
Recent Scanner Results:
O2 Upstream Sensor: O2SB1S1 voltage from .105 to .88 in constant switching pattern at idle. About the same readings at 2500 RPM (of course, switching pattern occurs more rapidly). All seems normal.
O2 Downstream Sensor: O2SB1S2 voltage from .3 to .825 in constant switching pattern at idle. At 2500 RPM switching pattern occurs more rapidly. I get different results at different times, but always a switching pattern, which means the CAT is trending bad. (I say trending because the CAT must still be within acceptable limits since the CEL is off.)

Broken Air Intake Hose (very recent problem) Air intake hose cracked recently on manifold end. Immediately after temporary repair, LTFT = +10, and STFT = ~0 (to be expected under this abnormal operating condition). After OEM hose permanent repair, STFT and LTFT hovering around zero again.

What I don’t understand: I just realized after discussing this matter more with car owner/driver that the last two times the “intermittent” P0420 DTC occurred is just after I performed maintenance tasks (oil, filters, plugs) on car. (Twice in last year.) A few drive cycles after maintenance is done, the CEL is on. About a month later the CEL is off (~40 OBD2 drive cycles; I understand OBD2 drive cycles). I know with new plugs I’m affecting the exhaust gases and triggering the P0420. But I must admit I cannot truly explain why this cycle of events is happening. (Using NGK GP Platinum BKR6EGP plugs.)

Car is currently running “fine.” If I never looked at the results of various test I would think everything is great with the car. But tests suggest the CAT is going bad, the compression is too high (carbon build up), and performing maintenance (changing plugs, etc.) triggers a temporary P0420. And yet with all that said the fuel trims are okay. Don't know what to think about this engine.

Questions
Are dry compression numbers too high? 232/230/230/230. Indicative of engine carbon problem?

Again, don’t truly understand why bi-annual maintenance tasks are triggering a P0420. What is this telling me?

Any comments? Suggestions?
 

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Discussion Starter #16 (Edited)
10/18/12019 Update: This post contains final, wrap-up comments by author of this thread; posting these comments assuming it may help forum members.

Restating Problem: Intermittent P0420 DTC for last two years, and recently, from December 2018 to March 2019, CEL is on constantly (P0420 DTC). Car must pass state inspection March 2019, so I undertake repair tasks described below.

Problem resolution: I replaced primary CAT (catalytic converter), O2 sensors, and second CAT under engine/car (non-monitored, second CAT on 5SFE). I also replaced a number of upstream components described below. This is a one owner garage parked car, it remains in family, and is driven daily. Accordingly, I made conservative decision to not only replace CATS but also various upstream components that will help to extend life of engine.

Car runs great given many new components installed in last year.

What I Learned Over Time, and Probably What is Important to Pass On (key points):
  • CAT is normally killed/degraded by upstream problem(s). It is important to maintain engine so CAT is not degraded. Extreme problems like radiator fluid contamination (through head gasket) or an engine burning too much oil, for whatever reason, will quickly cause CAT problem.
  • OEM CATS are best because EPA mandates that certain critical emissions components on new cars (CATs fall into this category) must be covered by manufacturer’s warranty. Long story short: OEM CAT contains more precious metals than third-party CAT; third-party CAT sold in automotive aftermarket is not held to the same operating standard or warranty period by EPA (the law).
  • Given previous facts, I would always install an OEM CAT on younger car, or a car that I intended to keep for some time.
  • CAT is suppose to last life time of car if engine is well maintained (that’s the goal anyway). However, O2 sensors may need to be changed around 100K mileage mark. O2 sensors will likely NOT last life time of car.
  • After installing new third-party CAT, and after inspecting the old CAT closely, I believe I likely had an O2 sensor problem, and not necessarily a CAT problem, which turned on the (intermittent) check-engine-light. I didn’t test/replace sensors independent of CAT. This was my rookie mistake in not fully understanding that O2 sensors may fail well before and independent of CAT.
  • I watch fuel trims now like a hawk. Anytime I work on car, maintenance or repair work, the scanner goes on the car. I check fuel trims and watch O2 sensor values to make sure car is operating properly. If you are going to work on your vehicle you need a scanner; it will make a difference - there's just too much useful data available from a scanner not to own one. You also need a digital multimeter. Optionally, a clamp multimeter (amperage readings) and a carbon pile battery load tester are useful.
  • Toyota Nation Forum members are a great resource, and the Haynes Techbook OBD-II and Electronic Engine Management Systems manual contains a wealth of practical information. If you have a scanner, and I do, read your scanner operators manual, its informative also. I read a lot about emission systems and watched several useful videos as recommended by forum members. Until recently, I was not sensitive enough to the inter-relationships of emission control subsystems and what the PCM (computer) was doing with all its sensor inputs. Now, after much reading and learning, things make a lot more sense these days.
Upstream Components Replaced
Since upstream components cause CAT problems I took that message to heart because we intend on driving this car for several more years and I want it to run reliably. Thus I replaced several upstream components as described below.

Ignition System and Other Emission Stuff: In December 2018, replaced spark plugs, plug wire set (Denso), rotor and distributor cap. Also replaced PCV valve, grommet, and hose (OEM parts). Air intake hose cracked this month, so replaced it with OEM hose.

Vacuum Hose: Replaced most but not all vacuum hoses (leaving EVAP subsystem alone for time being). No vacuum problem with this Camry, steady at 22 Hg. Happy about that.

MAP System: March 13, 2019. Replaced MAP sensor, electrical connector, vacuum line, and related gas filter. Accidentally broke vacuum hose nipple on sensor removing vacuum hose – that’s the only reason for replacing this EXPENSIVE sensor. When replacing sensor also broke electrical connector. Dang. These older plastic parts are really brittle.

EGR System: March 14, 2019. Replaced EGR VSV (left in original position). Also replaced EGR valve and modulator, including vacuum hoses running down to VSV. Cleaned EGR tube, installed new ferrules, gasket, etc. (In case you’re wandering, EGR valve exhaust passage was 55% closed off due to nasty thick oil residue.)

Conclusion
Exhaust-Emission Repair.
April 23, 2019. Installed exhaust parts: CAT (Magnaflow), O2 sensors (NTK), and secondary CAT (Walker Exhaust). I’m normally proponent of using OEM parts, but the OEM CAT and exhaust parts (if available) are expensive. Due to age of Camry, I reluctantly decided to go with certain aftermarket exhaust parts.

Have run scanner, compression test, vacuum test, and various electrical system tests on car at 214K mileage. Everything tests good. No reason for this Camry not to join 300K mileage club. The GEN3s are well built vehicles.

Rest of this post is of a general nature, maybe helpful for some.

EGR System:

  • Regarding ERG valve tube compression nuts: I purchased Snap-on 24MM 3/8 crowfoot wrench to remove bottom compression nut. (Couldn’t break it loose with crescent wrench.) This crowfoot wrench worked wonderfully (wonderfully expensive also). Used liberal amount of PB Blaster on compression nuts.
  • So that you know: you can pull new vacuum hoses from modulator and valve to VSV inside the original protective sleeve (on back side of engine). I taped new vacuum hose to original hose, and then pulled original hose from underneath engine (one hose at a time). These hoses did slide thru the protective sleeve without too much trouble.
  • I removed and installed VSV and bottom compression nut on valve tube with front end of car on steel ramps. Of course, it’s necessary to remove splash guard to gain access to VSV, but I did not remove front passenger-side tire while performing VSV replacement. Used my Craftsman creeper to slide around under car.
 

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Discussion Starter #17 (Edited)
if you eliminate the cat as a problem, then you might have a defective up or downstream o2 sensor that's giving the ecu bad input info, causing the ecu to throw an errant cat code. have you replaced any of the sensors? if so, which one(s) and at what mileage.
tony
Update: 10/23/2019 - - So that other forum members benefit from this thread . . . After much reading, after much learning, after inspecting CAT, which I did replace even though it did not look bad, after learning that O2 sensors do fail independent of CAT and are generally only good for about 100K miles, I believe Mr mcgowaw was correct in his assertion that I may have a bad O2 sensor. I realize visually inspecting CAT is a non-scientific approach, but the CAT looked really clean, so much so that I just knew instantly I should have replaced the O2 sensors first.

Even though both O2 sensors were replaced 40K+ miles earlier, this Camry is driven on so many short, slow speed, in-town trips (car never sees interstate), that I would not be surprised to see sensors or CAT go bad early. This Camry engine exhibits high carbon buildup condition (revealed in compression test), which basically can go hand-in-hand with emission problems like P0420 DTC.
 
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