Q: air pump check valve on 2002 Cadillac DeVille DTS

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code 0410 air pump is working fine good air flow. code comes on .was told to check the check valves where are tey located & how much of a problem are they to replace if neccessary. what is the procedure to replace or how do I check them to see if they are good or not spud 40
(1) Answer
Really, the best way to deal with a Secondary Air System code, P0410, is to fully inspect the whole system. Since you most likely do not have a scanner, you will need to cold start your car and then test the system while the car is cold.
The Check Valves are not too hard to replace, but they may not be what is wrong. I do Emissions work in CA and some of the GM cars with P0410 are check valves problem, but sometimes the system is plugged with carbon, or the air control solenoid is fried or ....... you get the idea.
Here is link to a Website that has very good online repair manual information, there is small fee but it is well worth it.