I'm getting a check engine light from a code #11 (Air Injection System).
I went ahead and changed out the air injection (smog) pump with a good used one (made sure the clutch engaged when energized and made sure to clean out the check valve and other parts of hose system that connects to it). The pump clutch engages at warm-up and then turns off. After about 5 minutes at idle, it will turn on again for just about 10 seconds, and then repeat the interval going forward.

Any info on what tells the pump to turn on? What conditions triggers it turning on? What I need to check next?

In case it makes a difference, I also changed the EGR and the OXY sensor with new parts last week so that it would pass smog. It did pass smog with acceptable emission levels, but also because we reset the check engine light just before the test.

Thanks.

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03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio