Fault codes po420 and po430

Yesterday, when I started my car, the check engine light came on. The car seemed to be running good, and I was far from any shop or city (Hwy 126) in california so I drove the car home slowly (15miles). This morning my friend has a duramatic or something like that and checked and the codes that came up are po420 and po430. His machine cleared the check engine light. Does anyone know these codes or where I can translate those codes??

Quotes source post: 9755485

Renntech if you join -- highly recommended! -- has a section where you can search DTC (diagnostics trouble codes). No need for me to search; I know these by heart (and besides I have other references at my disposal). P0420 - TWC (3-way converter) efficiency low, cylinders 1-3. P0430 - TWC (3-way converter) efficiency low, cylinders 4-6. Sometimes an error on one bank triggers a similar error on the other bank. But in this case I think there is a common failure. First though the guidelines are to if there are any error codes associated with aging O2 sensors to replace the indicated sensors, clear the codes, then drive the car long enough and in such a way to give the DME plenty of time to flag the converters. Be sure the test equipment your friend used read all the codes and he also checked for any pending codes. If he did not you may not have the full picture. There are 5 tests the test steps too lengthy to type in. But they all end testing some aspect of the EVAP system. Test 1 tests the installed position of the canister purge valve; Test 2 tests the triggering of the EVAP canister purge valve; Test 3 tests the voltage supply and leads of the canister purge valve; Test 4 tests the purge valve (using a vacuum load); and Test 5 tests the hoses between the EVAP canister purge valve and intake system. There's a common thread in the above, to state the obvious. The EVAP canister, or its valving, or its electrical connections, or its associated hoses are suspect. This is a common failure and would account for the concurrent appearance of the faults on two different cylinder banks. If you supply me with a suitable email address -- use private email -- with a request for the test steps for all the tests I listed above I'll make a PDF copy of the test steps and send it to you. Sincerely, Macster.

Thank you, I sent you a PM

I have come to the conclusion that I may have overfilled my oil at the last oil change several days ago. Is it possible that this caused those fault codes Appreciate any advice or suggestions

Quotes source post: 9757681

Whether the overfill caused the codes or not I can't say with any certainty. My advice would be to first remove the excess oil. Unless you know by how much you overfilled the engine and can remove this amount my advice would be to drain the oil as you would at a regular oil change then add in the required amount of oil minus the amount that the oil filter housing would add to this amount. By way of an example if the engine requires say 8.5 quarts of oil with an oil filter change instead add just 8 quarts. Or a bit less. Count the empty bottles twice to be sure you have added this amount. Then check the oil level according to the owners manual and top off the oil to bring the level up if adding the lesser amount left the oil level too close to the low end of the level. Clear the codes. Drive the car. See if the codes come back. Now if you severely overfilled the engine with oil it can take time for this oil residue to make its way out of the engine. Thus while you drive the CEL can come back on. It might be due to same codes or they might be different, perhaps related to the 02 sensors. How much to drive the car? Allow roughly 50 miles of driving. A long story goes with this number, but I won't post it here. Also, not all cases of dousing of the engine internals with oil results in sick converters or O2 sensors. The converters maybe just be bad because it is their time. Correctly address the overfilling of the engine with oil. Get that oil level down to between the low and high lines. Drive the car and see what happens. What happens or doesn't happen determines what you do next. Sincerely, Macster.

Quotes source post: 9760051

Macster, I took you advice and drove to a local VW shop and asked them to remove about a half quart of oil from the car. They did it, and then I had my buddy remove the check engine light and drove the car very gingerly. That seems to be the trick. No more check engine light, and the car seems to be running as it was before the fault codes. I took it out yesterday to Pomona and jumped on it a little and it responded like a new car. Thanks for all your help and advice

Don't want to rain on your parade but that gingerly drive may not have given the DME the drive cycle it requires to perform a full check of all systems. With an OBD2 code reader/data viewer you could query the DME and the readiness monitor statuses and if these are set to complete then you would have a higher degree of confidence things are indeed ok. But don't sweat it. Just continue to drive the car and see what happens. My caveat to the preceding advice is to always pay attention to the engine and how it runs/sounds/acts. If at any time it starts acting up shut off the engine as soon as you can and avoid starting it again. I do not expect anything serious to go wrong, I just like to cover all bases. Oh, are you sure the oil level is ok? Not too high still? And not too low? Sincerely, Macster.

The oil level is fine, keep a close watch on it Thanks again, Macster