Codes p 0410, 0411, 0412 all refer to the secondary air injection system--malfunction, incorrect flow detected and circuit malfunction ===causes are --wiring--sir valve---air solenoid--ECM--air pump, air hose/s--ECM
code p 0491 refers to secondary air injection bank 1 --malfunction or insufficient flow=== causes are the same with a mechanical fault added
so to analyze -- the most common cause is air hoses, followed by valve or solenoid of the air injection system followed by ECM which be as little as a bad pin connection in the wiring
SOURCE: I FAIL THE EMISSIONS CODE# P0410- SECONDARY AIR INJECTION
I have a 2001 STS that had the same problem - Service Engine light and returned the P0410 code. It ended up being a small rubber hose that had pulled off one of the plastic lines in the secondary air system. In fact, I just fixed this last night.
Pull off the top engine shield (the one covering the motor and the fuel injectors, not the plastic one at the front of the car) and look for loose lines, hoses or wiring.
Also - if you remove the shroud under the engine (you just have to pull out a bunch of plastic retaining plugs) you can get at the lower elements of the SAS. Look for loose lines, hoses or wiring.
You could be fortunate and just have a loose line. Does the caddie run OK?
SOURCE: Diagnostic trouble codes P0410, P0491 and P2257
I believe it could be a faulty oxygen sensor or blocked air tubes. Check to make sure air pump is operating.Check green and black wires between pcm and pump relay. Check for 12v power between these two wires with key on check the wires for damage as this has been a problem area on these vehicles. Hope this helps.
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