Drive Accord Honda Forums banner
1 - 14 of 14 Posts

·
Registered
Joined
·
39 Posts
Discussion Starter · #1 ·
Driving on highway last week and check engine light came on. Based on a troubleshooting video I saw on Eric the Car Guy, I used a scanner with live data to see how the O2 sensors were working...see video below.

http://youtu.be/cFhLm7pC8z8

Temperature at Cat is (at idle speed):

Inlet: 195-252 degrees
Outlet: 240-300 degrees

Previous owner said forward O2 sensor was replaced about a year ago. The rear O2 sensor (36532-RAA-A02 SENSOR, OXYGEN-DENSO) has a frayed covering; not sure what effect that is having on the situation. See pic.

Any input is greatly appreciated. Again, 193,000 miles on '07 Accord EXL 4 cyl MT.

Funny thing though... Right after videoing the live scan results, the check engine light went out after having been on for 1 week. (Not sure if it's something I did with my scanner or not).

BTW, I just got this scanner--what does the "G" and the "?" mean on the right side of the screen?
 

Attachments

·
Registered
Joined
·
1,279 Posts
The frayed wire covering should not be a problem.
At your mileage the converter is likely not able to always meet the efficiency test run by the car's ECM. The converter may still be operating at 90+% but Honda set the P0420 alarm limits quite high compared to some other cars.
The alarm may come and go for a while but eventually it will stay on unless you change the converter or take other measures.
 

·
Registered
Joined
·
39 Posts
Discussion Starter · #3 ·
Thanks for the response. Any idea what the general life expectancy of a Honda cat is?
 

·
Registered
Joined
·
1,279 Posts
I think the life span varies a lot depending on factors like fuel quality, driving conditions (short or long trips), engine oil consumption, etc. My sons 98 started throwing efficiency codes at 100k, my 2000 now at 168k has never had a converter problem. Assuming yours is the original converter it has done well to go nearly 200k.

If you are considering a replacement, I hear the Honda dealer replacement converters are more costly but last longer than the aftermarket converters.
 

·
Registered
Joined
·
4,851 Posts
According to the what I read “G” -- Indicates graphic viewing is available. So you can view a graph of the O2 sensor on the scanner. That is good information to see as the readings are not too helpful but the graph of the second O2 sensor will show the story as only the second 02 sensor is used to determine if the Catalytic Converter is below efficiency.

While Catalytic Converter do fail, it is more likely it that some problem caused it to fail. The biggest issue is too much fuel or a rich mixture issue. Take a look at the freeze frame data, this will show the conditions at the time the DTC was set. I would concentrate on the fuel trim at make sure that it is closer than + or - 8% anything above and below that there is some other issue else going on and the ECU is compensating.

If the fuel trim looks within range it is time to look at the O2 values. The front O2 sensor should be switching from rich (over 600mV) to lean (under 300mV) and the rear O2 sensor, or converter monitor, should be a nice, smooth line with minimal variance in mV. When looking at the values of the O2 sensors pay particular attention to the switching rate of the sensors and be sure that neither the front nor rear sensor drops out or spikes for extended amounts of time. If either a slow switching rate or spike/drop-out happens, but the O2 then recovers and appears to be operating normally, the O2 sensor may be starting to deteriorate – or as a lot of people say, “It has become lazy” and may need to be replaced.
 

Attachments

·
Registered
Joined
·
39 Posts
Discussion Starter · #6 ·
All I can say is...wow! That will prove very helpful. When I get a chance, I'll post the results you talked about.

Thanks again!
 

·
Registered
Joined
·
39 Posts
Discussion Starter · #7 ·
Freeze Frame Data

Freeze Frame Data attached 1
 

Attachments

·
Registered
Joined
·
39 Posts
Discussion Starter · #8 ·
Freeze Frame Data

Freeze Frame Data attached 2
 

Attachments

·
Registered
Joined
·
39 Posts
Discussion Starter · #9 ·
Freeze Frame Data

Freeze Frame Data attached 3
 

Attachments

·
Registered
Joined
·
4,851 Posts
So it looks like the car was fully warmed up and the long term fuel trim was 8.6%, that is a little high, also short term fuel trim was at 8.6% so combined that is 16.2%, it will not set a code until the long term fuel is + or - 20%. The only thing I could not tell from the pictures is if it was + or - ? I suspect that it is + or positive. That means the long term has moved the base 8.6% leaner and the short term moved it another 8.6%. The Long term fuel trim is the coarse adjustment and is stored in the ECU the short term fuel trim is learned while the engine is running, and is erased when you turn off the car. The long term tries to keep the short term fuel trim in acceptable ranges. Short Term Fuel Trim (STFT1 and STFT2) is the computer’s immediate response to adjust the air/fuel ratio. In positive corrections, fuel is added to adjust for a lean condition, while negative corrections respond to a rich condition. STFT corrections represent the current engine run cycle and react very quickly to O2 sensor input.

So it would seem to me that you have a lean condition going on and the system is adding more fuel to compensate. I think if you get the lean condition fixed your P0420 code may disappear. Here are the things that create the lean condition.

Running too lean – High positive fuel corrections can be traced to MAF and O2 sensor faults, vacuum leaks from intake gaskets/hoses, unmetered air (intake snorkel leak), clogged or dirty fuel injectors, fuel delivery issues, EGR valve leaking and exhaust restrictions such as a clogged catalytic converter.

So I would look to make sure you have no vacuum leaks something as small as the dipstick having a missing o-ring seal can cause this, if all vacuum lines look good and no visible vacuum leaks, I would clean the MAF sensor with the approved cleaner first using CRC/Mass airflow sensor cleaner part #05110. Graph the O2 Sensor 1 looking to see if it has drop outs and or is lazy switching. I would be concerned if when that O2 sensor was replaced before it was replaced with an aftermarket O2 sensor, it has been my experience that the manufacturer product is higher quality. I would concentrate on getting the Long term fuel trim down to around 1% or 2% and see if that cures the code P0420. It is entirely possible the catalytic converter is clogged creating this condition as well, if you could drop the catalytic converter and look down the inside to visually inspect that would give a quick answer.
 

·
Registered
Joined
·
4,851 Posts
A quick way to check to see if it is a Vacuum leak or a MAF sensor issue, is to look at the Long term fuel trim at idle and then increase the RPMS to 2500 and hold and watch the Long term fuel trim if it goes down it is a vacuum leak, if they go up it is a MAF sensor issue.
 

·
Registered
Joined
·
39 Posts
Discussion Starter · #12 ·
I've got some homework to get to!

Thanks again
 

·
Reverse Gear
Joined
·
989 Posts
curiously, I also have a 2007 manual transmission accord with CEL and p0420. Curious if you got to the bottom of the issue. I can't believe that the CC would go at my mileage of 107,000 mostly highway miles. My CEL will only come on when doing highway driving. It will go off after a day or two of non-highway driving.
 

·
Registered
Joined
·
39 Posts
Discussion Starter · #14 ·
Sorry BenzAccord, I was away from the site for a while. No I didn't solve the problem. I now that winter is over I need to clean the maf sensor and run some sea foam through the engine. The light has been coming on less frequently now, so it hasn't been a pressing issue.
 
1 - 14 of 14 Posts
Top