Southern Man

CEL came on yesterday, although car runs fine. Plugged in friend's OBD and it threw out code 491, "secondary air injection, bank one". Reset it and so far so good. Any suggestions on the cause?

Petersa9

Check the hose from the air pump in left rear of engine bay. There are also some schematics lurking around the forums. I had the same code and the hose just popped off after replacing my AOS.

Southern Man

Thanks, but that connection seems fine. Checking everything I can see in that area, but may have to get under it.

kromdom

Ahsai

Do you have a scanner that can diaplay O2 sensor voltage in real-time?

If the hoses are fine, you need to monitor the O2 sensors to diagnose it further. It could be bad O2 sensors or secondary air ports clogged from carbon.

Southern Man

i don't have access to scanner that reads O2 in real time.

Thanks for the schematic Kromdom. I'll check everything I can.

Drove about 20 miles today with no issues. This will return, I'm sure, so I know it isn't over.

Ahsai

The one kromdom showed above is for 996 turbo. You should use this ones instead
http://www.renntech.org/forums/topic...l-p0410-p1411/

If yours a MkII, the valves #2 and #4 are combined as one (merged into #4). After voltage visual inspection, there's not a whole lot to go on without reading the O2 sensors.