Long story short I have until next Wednesday to get this fixed. Freaking Atlantic Tire quoted me 1270 on a Cat alone and said with labor it would be close to 2k. I laughed at him and said I can get one 270 bucks at Autozone, and we have the equipment to replace it. However, if I can avoid this, as I don't really know if it's the Cat or if the O2 Sensor is going south.

So my ideas are I can shotgun the parts a it, but would rather not, or try and diagnose the issue. It's said that there's two O2 sensors..but when I'm under the car I only see the one right in the middle of the Cat unit...so is there an upstream an downstream on the Fit or not? I can't tell..Autozone shows a up and downstream when I look them up, At 200-300 a pop at that....I google it and see a Boch for 54 bucks. How can I test the O2 sensor? I have an ODB scanner that will give me real time data, and I've read you have to watch the voltage move up and down but not sure what I should be seeing. Also, is it possible to 'clean' the O2sensor?

Thanks,

C.D.

 

Look at the data stream for both o2 sensors. If the readings are mirroring eachother then the cat is bad. This is some good info for the o2 diag

 

So there are 2 sensors? Where is the other, since the one is obviously right there in the middle of the cat? I assume farther up towards the manifold? I can't get up under there right now to get a good look.

 

Off the exhaust manifold

Where is bank 1 O2 sensor? - Honda-Tech

 

Thanks speed! I'm going after the O2 sensors first, but from what I've heard it seems it could be unlikely...but hard to say. The code is not calling out the OS sensor..but the OS sensors are what is telling the ECU something is up...ugh.

 

Your welcome, not sure how many miles are on your car but the cat should be under warranty for 8year/ 80,000 miles

 

You have two O2's, one is in the cat or just before and the second in the S pipe/secondary cat pipe.The one in the cat is a Air fuel ratio sensor which is usually the first issue and most expensive $150+ second one is just a regular O2 or the down stream cat . if you have a code reader that shows you live data you can monitor the current it should be at between the two cats to see a issue (I can get voltage when i get to work tomorrow ) but depending on the voltage at the primary or secondary cat you can see if one or the other is going bad ....

the second one is to check air fuel ratio it sometimes leans it out like my scion tc did look at fuel trims if its a combined total of more than 10% your cat is not working
EXAMPLE
long term fuel trim
+40%
short term
-17%

another question do you have a K&N intake ?????? if so disconnect your battery take off your MAF sensor off the intake and unplug it grab some brake cleaner if it is covered in dirt spray it down air dry completly and then reinstall had that issue on my old honda and scion tc gave it a P0420 code and a lean code at the same time

 

Past that, unfortunately, right at about 95k.

 

Not quite sure what I should be reading on the scanner. It's a little Actron CP9575. It has the O2S reading but when I'm watching it's displaying O2S12(V) - Which I would take to mean O2 Sensor 1 and 2 voltage..but it fluctuates rather wildly between about .9 and .13..give or take, need to really watch it again. I don't know what it should be reading since it's giving me a single reading for (I assume) both sensor outputs.

K&N Intake? You mean filter? It's got a K&N Filter in it...but just the stock intake assembly?

 

yea the K&N filters have a oil based filter what happens is the oil gets sucked into the intake track covering your mass air flow meter . it then attracts dirt which could lead to a false code being thrown try cleaning than reset the code make sure to unplug and then clean it and give it a good 15 mins or so to dry after spraying it with brake cleaner

off to work will get you the correct current

 

Well, one problem here...doesn't appaer to have a MAS sensor, it's got a MAP sensor, which I did pull out and clean as it can cause the same kind of issue..but it didn't look dirty from what I could see...but did it anyways.

 

So a slight turn of events... I flashed my Actron to newer firmware now I have another OS sensor output, it seems. Theres O2S12(V) and OS211(Ma) The 12(V) runs around .7 to .9 as previously stated.. the OS211(Ma) Runs a lot lower, sometimes even dropping negative...curious. And my dam AIT senor, which I initially pulled out when looking for the MAS now is throwing a code for high input. Can't imagine I actually damaged it, it's nearly all solid plastic with nothing really exposed...oi.

 

So, I may be in the clear if I can get the Evap control cycle to complete. I cleared the codes again and this time the first Drive cycle everything completed within 15 mins or so or driving, the only thing left that is hanging me up (Assuming I don't throw another P0420) is the evap control cycle..which I have no idea how long that takes. Was told it checks when the tank is between 1/2 and 3/4s full? There's also and ECU update I'm likely to get done, there's a TSB out on the P0420 error that was put out in 2010 that calls this code out. Says it mis reads info at idle and mistunes things. Not sure if it applies to the 2008, however.

 

DTC P0420: Catalyst System Efficiency Below Threshold

NOTE:

• Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
• If some of the DTCs listed below are stored at the same time as DTC P0420, troubleshoot them first, then recheck for DTC P0420.

P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S (Sensor 2) heater

• P0300: Random misfire
• P0301-P0304: No. 1, No. 2, No. 3, or No. 4 cylinder misfire detected
• Poor quality fuel may cause this DTC.

1. Turn the ignition switch ON (II).
2. Clear the DTC with the HDS.
3. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on.
4. Test-drive under these conditions:

1. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the screen indicate EXECUTING?

YES - Go to step 6.

NO - If the screen indicates OUT OF CONDITION, go to step 4 and recheck. If the screen indicates PASSED, intermittent failure, the system is OK at this time. If the screen indicates FAILED, go to step 8.

1. Continue the test-drive until a result comes on.
2. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the screen indicate FAILED?

YES - Go to step 8.

NO - If the screen indicates PASSED, intermittent failure, the system is OK at this time. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 4 and recheck.

1. Turn the ignition switch OFF.
2. Replace the TWC.
3. Turn the ignition switch ON (II).
4. Reset the ECM/PCM with the HDS.
5. Do the ECM/PCM idle learn procedure.
6. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on.
7. Test-drive for about 10 minutes , varying the vehicle speed.
8. Check the CATA MONITOR CONDITION in the DATA LIST with the HDS.

Is the temperature OK?

YES - Go to step 16.

NO - Go to step 13 and recheck.

1. Test-drive under these conditions:

1. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the screen indicate EXECUTING?

YES - Go to step 18.

NO - Go to step 16 and recheck.

1. Continue the test-drive until a result comes on.
2. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0420 indicated?

YES - Check the fuel quality, then go to step 1.

NO - Go to step 20.

1. Monitor the OBD STATUS for DTC P0420 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?

YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 19, go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check the fuel quality, then go to step 1. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION, go to step 13.

 

i thought you had a GE for some dumb reason checked your profile and saw 08 fit lol but this is the diag steps to try

 

Thanks for the info, I'll see about giving it a try. It looks like it goes through 3 cycles before turning the MIL light on. I cleared the codes again today after cleaning the MAP sensor etc. and drove it around, mostly highway..then at the end of the third drive cycle it threw the error again, two of them..which is has always done..it's in there twice so I don't know if it was holding onto the code before making the call or what. Right now I'm in the lobby of a place waiting for my ECU to be flashed. There's a TBS out on this code and it calls for an ECU update. The scanner, at least, is not saying there's a problem with the O2 Sensors or anything else... so I'm wondering if all else fails I can boost the octane to get it to go stable long enough to pass inspection and I can working on root cause when I'm not in a time crunch.

 

Welp, starting to think I'm hosed unless the DA will let me extend the issue which I doubt. ECU update didn't fix it, it seems a little less forgiving now if anything..certainly changed some of the drive cycle stuff but still having the code pop up around the third drive cycle. I've noted right now it's already got the code in the memory but the MIL light is not on, guess is it pops it up after two checks, yes? That would explain why before it was showing two codes in the memory.

I'm still puzzled about the O2 sensor voltage. I took a video of the scanner and I'm guessing the O2S12(V) is the rear sensor and the O2S11(Ma) is the front? Or do I have that backwards? I suppose they could be fouled or just worn out. I do have nearly 100k on it and they've never been replaced but I would think that if they were giving out they would be throwing different codes.

Come Monday I'm either going to have to pay to get it analyzed to find out for certain and then either bite the bullet and (assuming it's the cat) buy a $1200 Honda cat or gamble on getting a cheap after market one. Ugh...just paid this darn thing off too and though I was scott free!