P0420 (0702)
Thread Starter
Joined: Jan 2007
Posts: 4,508
From: Wrentham,MA/Smithfield,RI
P0420 (0702)
Ok, I had both these codes about a month ago and decided to reset the ECU and see how long it took to come back. Well a month later both codes are right back at me.
P0420 (Catalyst Efficiency Below Threshold Bank 1) and P0325 (Knock Sensor and Wiring Harness). I am going to replace the KS and the wiring harness tomorrow as that code has been there over the last month (I checked periodically and only the KS code was there...)
The 0420 code has me a little confused. I have heard from some people that it is an 02 sensor that does the trick, and on others it is the actual catalytic converter. What is your input on the code and what should be done to fix it. I am currently getting about 19-20 mpg city and 25-26 mpg highway.
Thanks for your help again!
P0420 (Catalyst Efficiency Below Threshold Bank 1) and P0325 (Knock Sensor and Wiring Harness). I am going to replace the KS and the wiring harness tomorrow as that code has been there over the last month (I checked periodically and only the KS code was there...)
The 0420 code has me a little confused. I have heard from some people that it is an 02 sensor that does the trick, and on others it is the actual catalytic converter. What is your input on the code and what should be done to fix it. I am currently getting about 19-20 mpg city and 25-26 mpg highway.
Here is what the stickies say:
0702
Diagnostic Trouble Code 0702 points to a problem with the three-way Catalytic Converter.
The Cat is one of the principal components of the emissions control system. The Engine Control Module monitors the signals from the two front Oxygen Sensors and the one rear Oxygen Sensor. The signal frequency of each sensor indicates something about the condition of that sensor. A comparison of the frequency of the front sensors with the rear sensor indicates something about the condition of the Cat.
This malfunction was detected when the ratio of the signal frequency from the right bank front Oxygen Sensor to the signal frequency of the rear Oxygen Sensor exceeded a critical threshold value. This indicates that the Cat does not have enough oxygen storage capacity. The right cylinder bank is also called the rear bank. It is cylinders 1,3,5. Possible causes of this DTC include ...
- Three-way catalyst
- Exhaust tube
- Intake air leaks
- Fuel injectors
- Spark plugs
- Ignition timing
0702
Diagnostic Trouble Code 0702 points to a problem with the three-way Catalytic Converter.
The Cat is one of the principal components of the emissions control system. The Engine Control Module monitors the signals from the two front Oxygen Sensors and the one rear Oxygen Sensor. The signal frequency of each sensor indicates something about the condition of that sensor. A comparison of the frequency of the front sensors with the rear sensor indicates something about the condition of the Cat.
This malfunction was detected when the ratio of the signal frequency from the right bank front Oxygen Sensor to the signal frequency of the rear Oxygen Sensor exceeded a critical threshold value. This indicates that the Cat does not have enough oxygen storage capacity. The right cylinder bank is also called the rear bank. It is cylinders 1,3,5. Possible causes of this DTC include ...
- Three-way catalyst
- Exhaust tube
- Intake air leaks
- Fuel injectors
- Spark plugs
- Ignition timing
Thanks for your help again!
Thread Starter
Joined: Jan 2007
Posts: 4,508
From: Wrentham,MA/Smithfield,RI
I bought the car 3 months ago and since have put 2000 troublefree miles on it. It has 110K miles, and it is possible that it had a misfire before I got it (coils gone bad). I was thinking that it was the cat also, because I don't think I would have passed emissions with a bad 02 sensor.
im going to say its your cat for the fact that i got an O2 sensor code for my rear O2 once. so i would think they would be smart enough to not through a code that says "catalyst efficiency" if it was an O2. plus the O2 has nothing to do with how efficient the cat is. the rear o2 only monitors cat efficiency it does not make the cat efficient. therefore, if it were my car i would replace the cat.
EDIT: you can pass emissions with two or less monitors in the 'not ready' status. that may have been the case for you when you went because a bad cat certainly wouldnt pass emissions either. either that or the place just didnt give a crap haha
another edit: any idea how long those plugs have been in there? because if theyre bad then they wont be igniting the fuel completely(if at all) causing a rich mixture and sending liquid gasoline out the tailpipe. so if you have checked them out, you might want to do that.
EDIT: you can pass emissions with two or less monitors in the 'not ready' status. that may have been the case for you when you went because a bad cat certainly wouldnt pass emissions either. either that or the place just didnt give a crap haha
another edit: any idea how long those plugs have been in there? because if theyre bad then they wont be igniting the fuel completely(if at all) causing a rich mixture and sending liquid gasoline out the tailpipe. so if you have checked them out, you might want to do that.
Thread Starter
Joined: Jan 2007
Posts: 4,508
From: Wrentham,MA/Smithfield,RI
Well at least it gives me an excuse to get the y-pipe while I am at it. 
I was thinking it was the cat as well....and it is working alright, maybe not 100%, but enough to pass emissions. I will look into getting a new cat sometime over the summer. I think Warpspeed has a high-flo cat and y-pipe for $285. I'll look into it some more.
I was thinking it was the cat as well....and it is working alright, maybe not 100%, but enough to pass emissions. I will look into getting a new cat sometime over the summer. I think Warpspeed has a high-flo cat and y-pipe for $285. I'll look into it some more.
Thread Starter
Joined: Jan 2007
Posts: 4,508
From: Wrentham,MA/Smithfield,RI
Originally Posted by willard00
another edit: any idea how long those plugs have been in there? because if theyre bad then they wont be igniting the fuel completely(if at all) causing a rich mixture and sending liquid gasoline out the tailpipe. so if you have checked them out, you might want to do that.
not too hard. all you do is pop the coils out and then pop the plugs out and inspect the end. the back bank is a little harder than the front bank but still isnt bad as long as you have a socket set. i doubt your mechanic would check them for free though. unless he just used a spark tester to see if they were sparking. that would be an easy way to tell.
edit: you could probably even smell the raw fuel coming out the tail pipe if one cylinder wasnt firing.
edit: you could probably even smell the raw fuel coming out the tail pipe if one cylinder wasnt firing.
Thread Starter
Joined: Jan 2007
Posts: 4,508
From: Wrentham,MA/Smithfield,RI
I think that I would be able to tell as far as performance wise also. I am assuming that the coils were replaced (has 110K on a 99) and the car must of misfired during the period when the coils went....so that could of blown the cat. I'm in no rush to replace the cat....and I may just keep resetting it because it is not making a difference in my car's performance.
i wouldnt bother resetting it. it will just keep coming back. if its just a fluke and your cat is actually good, the computer will recognize it and shut the light off itself. if youre resetting it to pass inspection, dont bother. all the OBDII monitors will go to the 'not ready' status and you will fail and be told to come back in a couple weeks.
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