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Jerry Newton
Jerry Newton, Cadillac Technician
Category: Cadillac
Satisfied Customers: 4430
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Cadillac STS: I have a Cadillac STS 2006 4.6Liter where I

Customer Question

I have a Cadillac STS 2006 4.6Liter where I received an error code P0430. I have replace all four 02 sensors. My reading using a scanner is the same as before. Below are the readings at idle:
O2 B1 S1 (V) .037
O2 B2 S1 (V) .037
O2 B1 S2 (V) .680
O2 B2 S2 (V) .640
What do I need to do to fix the P0430 code?
Submitted: 1 year ago.
Category: Cadillac
Expert:  Ron Z. replied 1 year ago.
Unfortunately, the P0430 is a fairly straight forward code, and a fairly common problem. This code points to a failing Catalytic Converter for Bank2 (the one built into the exhaust manifold closest to the front of the vehicle). . Make sure there are no current cylinder misfires. Make sure there are no leaks in the exhaust system. Which, if there were, you should be able to hear. Sounding like a repeating "tick" or "puff" from the exhaust. Usually more prodominate when the engine is cold. Make sure to include the exhaust manifold when checking for leaks/cracks. If these check ok, then most commonly, the Converter is "on it's way out" and will need replacement in the near future. Keep in mind, you will need a replacement converter that meets specs. Those "universal" or "discount" converters sold at some after market parts stores do not meet specs, and will not cure a P0430. Please do the right thing and remember to leave a rating using the rating system at the top of this page or accept the answer so I may be credited for this Q&A. You can ask follow-up questions any time, even after you rate or accept.
Customer: replied 1 year ago.
I have a Cadillac STS 2006 4.6Liter where I received an error code P0430. I have replace all four 02 sensors. My reading using a scanner is the same as before. Below are the readings at idle:O2 B1 S1 (V) .037O2 B2 S1 (V) .037O2 B1 S2 (V) .680O2 B2 S2 (V) .640What do I need to do to fix the P0430 code?oscillateMy O2 B2 S1 sensor is reading .037 volts, straight line. Is this correct? Please comment on the values above.
Expert:  Jerry Newton replied 1 year ago.
.037 straight line is not a good thing, O2 sensor values should be a sine wave pattern on a scope. Scan tools are sometimes not fast enough to register this rapid cycling, so looking at static voltage numbers is not a good indicator of O2 sensor activity. You have to scope it to see it. We can't assume anything based on static voltage, and further, your ECM would be setting a code if the voltage was actually fixed lean. However, as the last expert noted, P0430 has nothing to do with oxygen sensors. P0430 sets when the ECM tests the converter by looking at pre vs post O2 values. Converters should add oxygen to the exhaust stream, so the computer anticipates seeing lower voltages on the post sensors than the pre sensors. This isn't the sort of thing that you'd be able to notice on a scan tool, the computer tests this under very specific conditions during the drive cycle, and monitors the sensor activity much the way a scope would report it. The computer software is savvy enough to detect a bad oxygen sensor, and it's exceedingly rare to fix a P0420 or P0430 code by replacing an oxygen sensor. People do this out of desperation, because it's cheaper to buy some oxygen sensors in hopes that it will fix it, but it almost never does. P0430 means you need to buy a new catalytic converter. That really is the long and short of it.

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