Help Diagnosing O2/Catalytic Converter
11-12-2017, 10:15 AM
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Help Diagnosing O2/Catalytic Converter
I believe this is a commonly researched issue, but for some reason when I searched for 'O2' (titles only) nothing came up. So if this particular problem has been discussed, feel free to redirect me to another thread.
My wife's 2005 V6 4Runner is throwing the following codes:
C1201 - Engine Control System Malfunction
P0420 - Catalytic System Efficiency Below Threshold Bank 1
P0430 - Catalytic System Efficiency Below Threshold Bank 2
Anyone have experience with this particular group of codes? Does it seem odd that BOTH P0420 and P0430 codes are thrown? I'm not very familiar with emissions systems, so forgive me. I have also researched the issue and it seems pretty complicated - especially if you don't have a good OBDII scanner. Anyone have any tips on diagnosing the problem without a nice scanner? Feel free to tell me I didn't research it enough. I did search. And I didn't find anything conclusive.
Thanks.
My wife's 2005 V6 4Runner is throwing the following codes:
C1201 - Engine Control System Malfunction
P0420 - Catalytic System Efficiency Below Threshold Bank 1
P0430 - Catalytic System Efficiency Below Threshold Bank 2
Anyone have experience with this particular group of codes? Does it seem odd that BOTH P0420 and P0430 codes are thrown? I'm not very familiar with emissions systems, so forgive me. I have also researched the issue and it seems pretty complicated - especially if you don't have a good OBDII scanner. Anyone have any tips on diagnosing the problem without a nice scanner? Feel free to tell me I didn't research it enough. I did search. And I didn't find anything conclusive.
Thanks.
11-12-2017, 02:04 PM
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11-12-2017, 08:08 PM
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Jumping straight into the idea of a bad cat certainly is bad way of diagnosis, but with the details provided, it is the most likely cause. Your codes.is simply an efficiency code. If you had a wiring problem you'd find circuit codes.
The likeliness of having bad downstream O2 sensors is extremely slim but possible. It's is however very likely to have bad upstream O2s. It's good practice to replace O2s every 75k or so. Over time they will begin foul and give inaccurate readings. The down stream O2s are less likely to foul as the cats usually burn up any extra fuel in the exhaust. The the upstream O2s however will begin to foul. When they do they usually will make your AFM richer when it doesn't need to be. This causes worse fuel mileage, less power, O2s to foul more and quicker and cats to over heat and quickly die out. A fouled downstream sensor is unlikely to set an efficiency code. Its actually less likely to set one even if it is inefficient.
The only other test you could do is check the cat temp with a infrared thermometer. Drive the car around for a while and make sure it's fully up to temperature. Aim the thermometer around the exit of the cats. It should be around 500*f or so. More is ok but it can be too high. Of your seeing close to 1000*f it's likely your car is running way to rich.
rich. If it's too cold then the cat is bad. If it's way to then the cat may not be shot yet but overheated and it's life has been significantly shortened. Check it and see.
Chances are you have bad cats. To do a proper repair you'll want to replace your cats and at least the upstream O2s. As stated before, a fouled O2 will quickly burn up a brand new cat.
The likeliness of having bad downstream O2 sensors is extremely slim but possible. It's is however very likely to have bad upstream O2s. It's good practice to replace O2s every 75k or so. Over time they will begin foul and give inaccurate readings. The down stream O2s are less likely to foul as the cats usually burn up any extra fuel in the exhaust. The the upstream O2s however will begin to foul. When they do they usually will make your AFM richer when it doesn't need to be. This causes worse fuel mileage, less power, O2s to foul more and quicker and cats to over heat and quickly die out. A fouled downstream sensor is unlikely to set an efficiency code. Its actually less likely to set one even if it is inefficient.
The only other test you could do is check the cat temp with a infrared thermometer. Drive the car around for a while and make sure it's fully up to temperature. Aim the thermometer around the exit of the cats. It should be around 500*f or so. More is ok but it can be too high. Of your seeing close to 1000*f it's likely your car is running way to rich.
rich. If it's too cold then the cat is bad. If it's way to then the cat may not be shot yet but overheated and it's life has been significantly shortened. Check it and see.
Chances are you have bad cats. To do a proper repair you'll want to replace your cats and at least the upstream O2s. As stated before, a fouled O2 will quickly burn up a brand new cat.
