Bates

Check engine light came on after a 4 minute warm up and a 2mile drive to the soccer fields this morning. These are the codes it's throwing off:
- PO491: secondary air injection system
- PO492: secondary air injection system

I have the "996 Turbo vacuum system" diagram. Do i just sort of nose around and look for something out of sorts?

Seems like a lot of folks run into these codes from a quick Google search.

wross996tt

Secondary Air Injection System, Bank 1 & 2 – Below Limit

Possible fault cause
♦ Secondary air injection pump is not triggered
♦ Secondary air injection pump does not work
♦ Air supply lines restricted
♦ Electric change-over valve does not function
♦ Air change-over valve does not function
♦ Vacuum system leaking

Yep, I'd guess vacuum system leak

JG 996T

I had those codes, cracked valve

Land Jet

I had those codes. Mine was a loose top on one of the diverter valves.

daytrip00

Same codes... cracked diverter valve...

Bates

All fixed. Cause was a worn out rubber seal on the shut off valve: 993-110-337-50. $78.15 for the part. $340 labor to chase down the problem.

Kevin

This is the DV > diverter vales, or bypass valves or Cut off valves (OEM definition)

Kevin

BTW, didn't you hear the honking sound on boost??

Bates

Uhhh...huh? Honking?

adam_

What he was asking was 'did you hear a honking noise when you accelerated hard- such that the boost gauge was showing boost?'

When a diverter valve fails, the internal rubber diaphragm ruptures and under boost this flaps about causing a 'honk'...think whoppee cushion like.

$340? Hmmm. And a stock replacement? Only one? First thing I did was prophylactic replacement with aftermarkets- both of them.

Bates

I did not notice the noises you described above. Thanks for the clarification.