CEL 0418 & 0419 Secondary Air Injection issue

[grover]

Edit: 491 & 492, not 418/419. (Should have written it down instead of thinking I'd rememebr it!) 2004 986S.

I replaced my AOS in July (mostly squealing vacuum in the crank case as the symptom with very little oil in the intake) and the oil that did suck into the intake manifold has long ago worked itself out, but CELs 0491 & 0492 come back every time I clear them. The timing can't be a coincidence (well, I suppose it could...), but I can't figure out how the AOS could have caused any issues with secondary air injection. Nor do I really understand what these codes mean, besides "secondary air injection". The code reader says 0491 is Bank A, and 0492 is Bank B. I'm pretty sure I can hear the air pump's whine on startup. The 40A fuse in the trunk is OK. Concerned that I might have knocked something loose during the AOS repair, I've double-checked the connectors on the pump and they seem good. The secondary air injection valves are buried, though, and I haven't dug them out to check for residual oil; logic applies that the vaccum should have been pulling oil OUT of the system, though, not sucking it in.

Q1: What are Banks A and B? Left and right cats? Signifying an issue with a common point of failure between the two?

Q2: How is the computer determining there's a failure? Could it be something completely unrelated causing the issue that the computer is misdiagnosing as secondary air injection?

Edited November 29, 2010 by grover

[wvicary]

There is a main vacuum line from the intake that connects to a junction fitting for the vacuum tank,secondary air and intake flap that can easily be broken or not connected. It is located very near the AOS so inspect it for damage.

[grover]

Double post

Edited November 29, 2010 by grover

[grover]

There is a main vacuum line from the intake that connects to a junction fitting for the vacuum tank,secondary air and intake flap that can easily be broken or not connected. It is located very near the AOS so inspect it for damage.

Is it the fitting right above the yellow circle in this photo? I disconnected it when I changed the AOS; I just inspected it and saw no flap, just a quick disconnect fitting. Nothing on the intake manifold side but a hole, either. Should there be a flap here? There's no signs of any oil in the line at least, that's always a good sign. The pump came on for about 40 seconds after I turned the car on. Exhaust was clear while the pump was running, but a bit of smoke (normal exhaust smoke I'm used to seeing on any car at startup) after it shut down.

Edit: and it's actually CEL 491 & 492, not 418. And I found another thread about it on the 996 forums that sheds a bit of light. Man, I hate troubleshooting vacuum leaks.

Given that the pump is running and exhaust is clear while it's running and only started afterward, can I assume the vacuum valves are actuating properly and the secondary air system is, indeed, pumping air into the headers, and the problem is somewhere else? Would a missing flap or a vacuum leak allow the vacuum switch to work properly, but cause other issues?

Edited November 29, 2010 by grover

[mikefocke]

I think you might want to go back and read the codes again and write them down.

418 exists, 419, 491 and 492 don't in my factory 5.2 and 7.2 DME docs for 986s.

It is usually a good idea to post the model and year of your car when posing code interpretation requests as it can make a difference..

[wvicary]

Directly above the yellow circle is a small black plastic vacuum line that connects to a black rubber junction fitting. These are the lines I'm referring to.

[grover]

I think you might want to go back and read the codes again and write them down.

418 exists, 419, 491 and 492 don't in my factory 5.2 and 7.2 DME docs for 986s.

It is usually a good idea to post the model and year of your car when posing code interpretation requests as it can make a difference..

Mike, that's why I got confused and said 418/419. But 418/419 were NOT the codes, 491/492 were. They're real codes, the reader says "secondary air injection bank A" and "secondary air injection bank B" but they're not in the Bentley guide. The 996TT thread I linked to above lists the codes as legit Porsche codes. In their case, it was a vacuum leak, caused by various failures of parts, roughly half of which don't exist on the 986S, but some do. I double-checked and cleared the codes again today and they haven't come back (yet), but always have within a few days of driving. (I'll take photos next time if you still don't believe me!) 5 months ago, I thought it was just excess oil from the AOS failure working its way through, but that was 6 months ago so I'm having a hard time convincing myself it will just go away for good if I ignore it long enough... Edited November 30, 2010 by grover

[grover]

Directly above the yellow circle is a small black plastic vacuum line that connects to a black rubber junction fitting. These are the lines I'm referring to.

I inspected these pretty closely, and didn't see anything amiss, aside from not seeing the check valve you mentioned. Where should it be?

[infocusf8]

If you suspect a vacuum leak perhaps it's time to do a smoke test on your system. The problem with codes is they rarely point you to a specific part but to a system. I had to have three smoke tests done to find a pin sized hole in the rubber bellows that is attached to the secondary air system vacuum tank. Replacing that only got rid of some of the codes and it took a really good mechanic to figure out that it was a small vacuum line under the intake manifold that had come loose from the diaphragm. Because it was under the intake manifold it could not be seen and eluded the smoke test.

[mikefocke]

I think you might want to go back and read the codes again and write them down.

418 exists, 419, 491 and 492 don't in my factory 5.2 and 7.2 DME docs for 986s.

It is usually a good idea to post the model and year of your car when posing code interpretation requests as it can make a difference..

Mike, that's why I got confused and said 418/419. But 418/419 were NOT the codes, 491/492 were. They're real codes, the reader says "secondary air injection bank A" and "secondary air injection bank B" but they're not in the Bentley guide. The 996TT thread I linked to above lists the codes as legit Porsche codes. In their case, it was a vacuum leak, caused by various failures of parts, roughly half of which don't exist on the 986S, but some do. I double-checked and cleared the codes again today and they haven't come back (yet), but always have within a few days of driving. (I'll take photos next time if you still don't believe me!) 5 months ago, I thought it was just excess oil from the AOS failure working its way through, but that was 6 months ago so I'm having a hard time convincing myself it will just go away for good if I ignore it long enough...

I understand and that is why I'm confused and looked at 2 different versions of the DME diagnostic manuals. What may be a code for the 996TT may have nothing to do with the year and model car/engine you drive. Readers can be wrong, or the manuals can be wrong. Good luck.

[Loren]

P0491 Secondary Air Injection System, Bank 1 - Insufficient Flow

P0492 Secondary Air Injection System, Bank 2 - Insufficient Flow

Possible cause of fault

- Electrical fault in power supply or line between relay and secondary air injection pump

- Secondary air injection pump relay mechanically faulty

- Mechanical fault in electrical secondary air valve

- Pneumatic secondary air valve faulty/sluggish

- Electrical fault in secondary air injection pump

- Mechanical fault in secondary air injection pump or secondary air injection pump blocked

- Vacuum system leaking

- Air hose to secondary air injection pump slipped off or constricted

Usually when you get both of these faults the air pump is not running at all. Start by checking the fuse and the wiring connection.