KevMaster

So wife reported SES on my 04 maxima. Scanned the code and there it is P0420. I am like no dyamn don't need catalytic converter repair right now. I then thought lets read all O2 sensor readings.

Car is in park mode. RPM = 1500
Here are the sensor behaviors:
Bank 1 Sensor 1 - switch fine between 0.2x to 0.8x Volts
Bank 1 Sensor 2 - switch fine between 0.2x to 0.8x Volts
Bank 2 Sensor 1 - Always stays at 0.6x or 0.7x Volts
Bank 2 Sensor 2 - switch fine between 0.2x to 0.8x Volts

Does this Bank 2 Sensor 1 appears to be OK? Does this bank 2 sensor 1 is throwing P0420 code?

That's strange because the sensor is at bank 2 while P0420 is belongs to Bank 1 catalytic converted.

Has anyone seen something like this? can an expert chime in?

Edit:
Here is the scanner screen capture.

NIKV69

Try a gallon of Lacquer thinner. Whenever I get that code it always works. I run a gallon through my fuel and exhaust 3 to 4 times a year.

KevMaster

I heard about Lacquer thinner but not to confident to use in gas tank. I kind of worry about seals and gaskets. Have you used this in your 6th ten maxima?


Today I drove the car to record O2 sensors behavior and here is what I noticed.

Here is graph I had set to observe:
--------------------------------------
|Bank1 Sensor1 | Bank1 Sensor2 |
--------------------------------------
|Bank2 Sensor1 | Bank2 Sensor2 |
--------------------------------------

Bank 1 Sensor 1 - stayed at 0.3x volts (except when at full stop it spikes to > 0.8x/1.2x volts) while Bank 1 Sensor 2 was switching fine between 0.2x to 0.8x volts.
Bank 2 Sensor 1 - stayed at 0.6x volts (except when at full stop it spikes to > 0.8x/1.2x volts) while Bank 2 Sensor 2 was switching fine between 0.2x to 0.8x volts.

Bank 1 Sensor 1 and Bank 2 sensor 1 were following each other.
Bank 1 Sensor 2 and Bank 2 Sensor 2 were following each other.

I am not sure how O2 sensor works and switches but posting this here anyway that might help someone.
All I am trying to see if it's an o2 sensor before worry about catalytic converter.
At the end a good repair shop can diagnose this better.

i8acobra

Bank 1 cats are very common. In all my time at Nissan, I've done maybe 1 Bank 2 cat and many Bank 1 cats. If I had to guess, I'd say the Bank1 cat gets a bit too hot due to it's location. The Bank 2 cat has good airflow around it due it it's location in front of the motor.

Voltage is important, but the frequency is what needs to be monitored. Consult 2 has a scope feature. Also, I'd monitor your bank 1 and 2 Alphas. If the Alphas are normal, it's almost certainly the cat.

KevMaster

Yeah bank 1 cats are known to go out in our cars. I was aware of this and was hoping for not to see it but ohh well….

As far as alphas in terms I understand the differences of switching patterns, the upstream sensors on both banks alphas are sync with each other with kind of jitter pattern except for the voltage level. B1 S1 stays at 0.3x volts and B2 S1 stays at 0.6x volts. Both do now show any swathing patterns except on full stop I can see both upstream sensors on bank 1 and bank 2 spikes to 1.x volts at the same time and then goes back to 0.3x volts for B1 S1 and 0.6x volts for B2 S1 and stays there.

Regarding to downstream sensors on both banks, the alphas are not syncing with each other all the time. I can see difference between both banks downstream sensors switching patterns. B1 S2 seems to producing uniform swathing pattern. B2 S2 kind of follow B1 S2 swathing patterns but not syncing completely. There are differences in swathing patterns.

Thanks for your help though…

Quick question, if exhaust leaks presents before Y pipe catalytic converter from long time cause pre-cats to gives-up considering car might have run rich? This is what I understood after speaking with an expert.

i8acobra

Bank 1 S2 is what sets this code. It's either the sensor or the cat, but unless sensor 2 is locked at a voltage and not moving at all, it's probably the cat.

KevMaster

Dyamn.....Bank 1 S2 is switching fine so in my case it's cat. Crap that's gonna hurt the wallet really bad.

Any recommendation? Cattman headers or simply get ebay/magnaflow cat?

i8acobra

Not familiar with either of those, so I'll defer.

NIKV69

Yep first time I got the low efficiency code that you are getting I did it and it cleared up immediately. I then did it a few months later as a precaution. Then didn't do it for awhile and code came back this past October. Put a gallon in and it fixed it again.

I think it's safe, can't be any more harsh than any over the counter fuel system cleaners they sell.

KevMaster

How did you follow the process? 1 gallon into full tank and kept driving until tank gets empty? or kept driving day by day till tank get empty? You're inviting me to try this even though I hardly use any additive.

NIKV69

I think you should. Scotty Kilmer suggests a tank that is just a little under half but I let my tank run almost out. I put one gallon pure Lacquer thinner and drive on highway at 70MPH for at least 100 miles. Works like a charm.

KevMaster

At this point I have no clue if rear cat is just clogged-up or melted/damaged. Car is still running fine and not losing any power. No metal rattling noise at start-up telling me cat has not started breaking-up yet.

I might dump lacquer thinner and burn the hell out of it until tank is empty (I mean until tank empty indicator turns on) then fill 3-4 gallon gas and burn that out as well and then fill the tank full to avoid excessive lacquer thinner resides in tank.

If it clears up code then I might buy some extra time to save-up and buy new cats. If it never come back then that's my luck. If it does not fix anything then I will have to slide plastic and pay off slowly. If it damage anything then I know I will be responsible.

What brand and where did you buy lacquer thinner from?

NIKV69

Remember you can get the low efficiency code even if the cat loses just a little efficiency. So you won't see you engine run any different. Go to Home Depot and buy one gallon of Lacquer thinner. When your tank gets to a quarter full pour the whole thing in and drive on the highway non stop for 100 miles.

KevMaster

Driving it daily now. Work commute is short distance so it will take two weeks to get to 1/4 tank. Not in hurry to burn gas elsewhere to get to 1/4 tank. Meanwhile looking at magnaflow at the end to replace if nothing helps. No SES as of now and hope to see one before I burn paint thinner.

ACee

This will be interesting... I saw the scotty kilmer lacquer thinner you tube video but decided to handle things a different way. My precats were bad so I installed shorty headers vs running the thinner.

Has anyone else ran thinner before?

KevMaster

NIKV69 claimed he did. I am saying i'll do it soon but that may change.

NIKV69

Yep twice and jus as Scotty Kilmer said it cleaned out my CAT and trouble code went away. It works!

po8pimp

I wanna see this done. Post a video of how to. With the original opening of the thinner and codes pulled before and after.

NIKV69

Not much to it. If you get that code (Cat efficiency below threshold) go buy a gallon. Wait till your tank is 1/4 full, get a funnel and put it in. Drive 100 miles all highway speed. Very simple.

KevMaster

Even though Eric tried to prove Scotty wrong (matter of fact he used less amount of thinner and wrong amount of fuel in tank), but at least he tried thinner in his car means he didn't feel anything wrong using thinner in tank and drive 100 miles or so.

If cat us burnt/melted, no thinner is going to help. If cat is clogged-up (sea foam could be one reason) then thinner might clean-up cat.

Fizeau

I wanted to add my experience. Having issues I found the lacquer thinner trick, but could not find someone who posted experience miles after the fact.

I have a 2003 with 170,000 miles on it. I have codes for rear/downstream O2 sensors on and off for a year or so. Then I got 0420 as well. Since the car tends to drink a little oil I figured the cat may be clogged and the lacquer thinner might work.

I put the gallon of lacquer thinner into half a tank and at first put a stick on the accelerator to get RPM's up to 2500. Within minutes the catalytic convertor began to smoke slightly. This resolved shortly.

After 20 min I drove the car for about 100 miles. No problems with acceleration or Performance noted. I ran the tank down and filled it up, cleared the codes and waited.

No codes for 500 miles. Then I got the same ear/downstream O2 sensor codes I had been getting. I then changed the sensors figuring 10 years was a good run.

Since then (another 250 miles) no codes whatsoever. No noticeable difference in performance. It certainly did not cure my O2 sensors, but may have helped the catalytic convertor.

KevMaster

Before dumping lacquer thinner I had two P0420 codes.
1. Pending P0420
2. Stored P0420

Dumped lacquer thinner and drove 100 miles until empty gas light came on. Refilled gas just enough to drive 100 miles back until empty gas light came on.

Later filled full gas tank and scanned codes again...
1. No Pending code, cool !!!
2. Stored P0420

Cleared the stored P0420 and I will report back if I get P0420 code again.

$20 lacquer thinner
$25 gas to drive forth and back

Worth a shot.

NIKV69

Well done sir!

KevMaster

Thanks NIKV69

Its been only 70 miles driven after burning lacquer thinner so it will be interesting to find how long car stay out of P0420 code. Car indeed gained pretty good response. Must be clogged cats got cleared

NIKV69

Do it again whether you have the code or not. I do it every 4 months or so.

KevMaster

100+ miles and P0420 came back ON.

It was a great ride burning lacquer thinner

Oh well not happy but gotta get repaired done soon.

NIKV69

That was quick, mine took awhile to come back on. Try it again.

KevMaster

Nah man....just got the magnaflow for $230 shipped.

NIKV69

Cool, is that the pre cat? Take some pics of the job! I may have to do it one day.

KevMaster

Yeah it's a pre cat. Don't want to upgrade whole exhaust as timing chain or transmission issue may be ticking on clock, have not seen yet at 166k miles though.

Went to dealer last night and they offered 2014 rogue basic model for $19k minus trade in for maxima (I am sure they will low ball) on spot if I go though finance with them. Damn if it wasn't for maxima then I might have traded in on the spot

Ludxima

iTrader: (1)

I don't know about the magnaflows, but I bought the racingline hfpc hoping it would get rid of the code. It did for only a month. Hope you get better results!

KevMaster

Once magnaflow get installed then I am going to beat the hell out of this car for three months. I will put as much miles as possible. If it does not break within three months then my luck but if it does break and throw P0420 again then I can throw magnaflow back to store for warranty replacement. Yes I will be out of pocket for labor but a reputable shop that I know for long only charging me $90 to get it installed anyway.

Yes magnaflow went down with quality and uses low grade material now days thats all the information I gathered from online but I can't say this for sure.

Also I do not require to check emission every year. The only reason I am replacing cat it to avoid catastrophic engine failure if honey comb get sucked back in engine.

The other alternative is to hollow out cat and install back again. However I hate the idea of back pressure will going to be different for front and rear cat unless I hollow out the front one as well for no reason.

I will update ya how this go.....

maxlk

I was about to order some racing line hfpc... Guess I'll try the lacquer thinner first now

KevMaster

It's strange after turning SES off it comes back exactly after little over 100 miles. It happened 4 times so far. May be this is normal for car to throw P0420 code.

Getting replaced cat this Saturday. Mine was not clogged but damaged or burnt/melted cat I guess.

KevMaster

Received the Magnaflow. However I am not too impressed with the quality. I was unable to find the close-up images for magnaflow rear cat converter so I gambled. Here are some snaps to look at it close. Its tiny than what I was thinking. I tool pictures with 11 x 8.5 standard size paper to compare the size of this cat. Also the honeycomb material is not uniform and kind of already broke off as you can see in picture 4 and 5. Is this normal or should this cat go back to store again? I hardly deal with exhaust so I am not sure this is normal looking cat inside. Any feedback will be appreciated.

NIKV69

Wow very interesting, keep us posted!

KevMaster

Exhaust leak. That was diagnosed by shop.

I used to get P0420 and I was clearing that code OFF however after 100 miles it was coming back. Burnt lacquer thinner and SES came back after 100 miles again. So I bought the cat to replace and I was waiting for SES to show up again.

This time around after 130 miles SES did not turn ON. Regardless I went to shop to replace the cat. They jacked up the car and diagnosed exhaust leak at flex joint (that was repaired else where long ago).

Its kind of surprised because I did not hear exhaust leak while driving. Probably a small crack to notice. Shop said they are confident the leak was throwing P0420 so they advised to wait and watch.

Paid $40 to fix exhaust leak and drove another 30 miles and still no SES light. Car also ran little smooth after shop fixed the leak so that tells me leak was there but it just I didn't knew about it and I thought the noise while driving the car is normal due to age of the car.

Interesting.......I am still holding on to the cat I bought just in case SES light comes back on again.

I will keep update ya'll on progress.

KevMaster

Thought update you with miles driven.

100 miles - No SES
200 miles - No SES

Ludxima

iTrader: (1)

Wow! That's great news! I'm going to have to check mine for leaks as well.

wanna_be

Want to thank everyone in the thread that mentioned the lacquer thinner trick. I had the CEL and bank 2 code for the last 4 months and put in a can of lacquer thinner and now the code is gone and I have driven 300 miles. Was able to pass my emission test without a hitch