Old thread, but I'll post up my solution for a future lurker (like I was).

I had the same code - and there is a second mass air flow sensor as indicated in the prior post. I tried to clean mine as well - no resolution.

I then removed the valve to make sure that it wasn't stuck. It wasn't so that removed that as being possible.

I then removed the hose that attaches to the air pump to the valve and started the car (it has to be cold). The pump ran for about 30-45 seconds and sounded like a vacuum cleaner as it should.

Final possibility was the mass air flow sensor as well. With the car running I backprobed the wiring harness with a DVM. The ground was good, the 12V supply was good, but the third wire (which was the signal wire) was reading 0V - meaning it was not returning a signal to the computer and triggering the SES code.

No cleaning would take care of that - so I had to replace it. I really didn't want to shell out over $100 for a new one. So I searched around and found a rebuilt one at RockAuto for around $50 after core return. I tried it thinking I could return it if it was a POS. But 1 week later no issues. Time will tell but so far - so good.

Hope this helps someone else.