E36 P1421 P1423 codes

1998 E36 M3 check engine light came on a few weeks ago
Autozone code reader found P1421 & P1423: BMW specific codes
A search of the net finds that these codes indicate low oxygen in both
exhaust manifolds. Nothing serious though - the oxygen is delivered by the secondary air pump for about 100 seconds after a cold start - now I know what that thing is that sounds like a vacuum cleaner.
The pump is actually fine and has no signs of corrosion which can be caused by exhaust gases coming back through a defective non-return valve on the manifold.
So I browsed around some more, and found that a relay in the main power distribution box can be bad, giving these codes. Pulled it and re-installed the same one, went to Autozone and had the codes reset.
Codes came back a few weeks later - pump still hums normally during a cold start, so I know it's not a serious problem, but does anyone have an idea what the problem is. Intermittently bad relay is my best guess.
Cheers
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While I agree with you completely that electronic woes can often be resolved by simply unplugging things and plugging them back in, you can't really expect it to work every time. I think you're right that the relay is bad and is probably also the least expensive possibility.

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On Sat, 28 Oct 2006 16:25:00 -0700, derek_mcquarrie wrote:

On mine ('99 328is E36 2-door) the vacuum hoses that actuate the valve on the exhaust manifold had rotted, causing the valve to open partially or not at all. The computer set the same codes you're experiencing... Replacing the hoses fixed the problem, and it's been trouble free for about 18 months since. Cheap fix!
Good luck with yours...
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P1421 and P1432? (not P1423)
These codes say that the secondary air system is not working correctly. The secondary air is the Air Pump and its plumbing that punps fresh air into the exhaust stream immediately after the exhaust leaves the head and enters the exhaust mainfold.

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Thanks. I know what the codes mean from the wonderful internet.
Even when the codes first appeared, there were no other symptoms of trouble; the pump was actually running during a cold engine start, there was no sign of pump corrosion, all the hoses looked OK.
The check engine light went out by itself about a week ago and has stayed off. I thought one needed an OBD reader to reset these warnings. any comments?
Jeff Strickland wrote:

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