Oxygen Sensor/ P0420/430 code C6
Thread Starter
8th Gear
Joined: May 2023
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Oxygen Sensor/ P0420/430 code C6
Hi guys,
In my 07 C6, error P0420 and 430 showed up. The obd diagnosis shows that there's a problem with one downstream oxygen sensor (bad voltage). I've changed both downstream Ox sensors but the code showed up again. What can casue it now?
In my 07 C6, error P0420 and 430 showed up. The obd diagnosis shows that there's a problem with one downstream oxygen sensor (bad voltage). I've changed both downstream Ox sensors but the code showed up again. What can casue it now?
Racer
Joined: Mar 2019
Posts: 382
Likes: 68
Hi, a failed catalytic converter will cause that.
Thread Starter
8th Gear
Joined: May 2023
Posts: 8
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Ok, it might be that thing but.... Can someone tell me how is it possible to get catalytic converter fail after 31k miles? To be honest, the car was "abandoned" for about 4 years from now. I mean, I buy it from a guy who wasn't using the car for such a long time. It was standing in a parking lot. But I can't imagine how can this happen to a car with so low milage.
Racer
Joined: Mar 2019
Posts: 382
Likes: 68
Ok, it might be that thing but.... Can someone tell me how is it possible to get catalytic converter fail after 31k miles? To be honest, the car was "abandoned" for about 4 years from now. I mean, I buy it from a guy who wasn't using the car for such a long time. It was standing in a parking lot. But I can't imagine how can this happen to a car with so low milage.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Ok, it might be that thing but.... Can someone tell me how is it possible to get catalytic converter fail after 31k miles? To be honest, the car was "abandoned" for about 4 years from now. I mean, I buy it from a guy who wasn't using the car for such a long time. It was standing in a parking lot. But I can't imagine how can this happen to a car with so low milage.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
What do you mean by “bad voltage” ???
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Ok, after the car is off for a few hours what millivoltage do your downstream O2 sensors show with the ignition on ??…they should show 450 millivolts which is their “bias voltage”…if they show 100 millivolts unplug the O2 sensor…if the reading now shows 450 millivolts on the scan tool the O2 sensor is bad…if it REMAINS at 100 millivolts you have a wiring issue…are your upstream sensors oscillating between 200-800 millivolts with the engine running at operating temperature??…the downstreams should be steady around 600-700 millivolts.
Last edited by C5 Diag; May 24, 2023 at 04:09 PM.
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Thread Starter
8th Gear
Joined: May 2023
Posts: 8
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Ok, after the car is off for a few hours what millivoltage do your downstream O2 sensors show with the ignition on ??…they should show 450 millivolts which is their “bias voltage”…if they show 100 millivolts unplug the O2 sensor…if the reading now shows 450 millivolts on the scan tool the O2 sensor is bad…if it REMAINS at 100 millivolts you have a wiring issue…are your upstream sensors oscillating between 200-800 millivolts with the engine running at operating temperature??…the downstreams should be steady around 600-700 millivolts.
I’m wondering if those new sensors need to be „reset” somehow?
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Safety Car
Joined: May 2016
Posts: 4,662
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From: Erlanger, Kentucky
Check your exhaust gaskets for leaks. Check all exhaust connections in the exhaust system, even downstream of the 02 sensors.
Check your exhaust manifold bolts for tightness. Re-torque them.
While it could be a bat cat, more commonly P0420 and P0430 are from exhaust leaks.
Check your exhaust manifold bolts for tightness. Re-torque them.
While it could be a bat cat, more commonly P0420 and P0430 are from exhaust leaks.
Team Owner
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From: Plantation Florida USAF(Retired) 1966-1990
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St. Jude Donor '05 thru '26
NCM Sinkhole Donor
I had the same code and clear it and it would return. I took the car to muffler shop, to check my catalytic converter they put it on lift and took there temperature to find my left was cool, and the right 400 degrees.
They didn't charge me cause they wanted my business and took it another shop, and it came with reading.
Might want to get it checked?
They didn't charge me cause they wanted my business and took it another shop, and it came with reading.
Might want to get it checked?
Thread Starter
8th Gear
Joined: May 2023
Posts: 8
Likes: 0
Check your exhaust gaskets for leaks. Check all exhaust connections in the exhaust system, even downstream of the 02 sensors.
Check your exhaust manifold bolts for tightness. Re-torque them.
While it could be a bat cat, more commonly P0420 and P0430 are from exhaust leaks.
Check your exhaust manifold bolts for tightness. Re-torque them.
While it could be a bat cat, more commonly P0420 and P0430 are from exhaust leaks.