maarp

My B5 threw me my first CEL last week. Took it to my local indie, he retrieved the code, and reset the light for me. Didn't do anything else, other than to tell me to come back if it comes back on. (Gotta love the indies )

Anyway - I've researched a bit, sounds like it's the secondary air pump. Ok, first question: What the hell is that and what does it do? From what I gather, it helps increase airflow on cold start-ups, which makes sense since the CEL came on just after leaving home on a freaking cold morning last week. Other than that, does it do anything? Should I be checking into anything else?

I appreciate the insight.

maarp

Anyone? Anyone? Beuller?

vgorous

iTrader: (1)

A4Cragman
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"Sounds like it could be two things. My first intuition tells me its just the secondary air pump clicking on. That pump is designed to run for the first couple minutes you start the car when the engine is 'cold' (specifically, I believe this is something along the lines of the coolant temp being below some specific temperature) and the function is purely for emissions, it pumps a little extra air into the exhaust mani to make the post-cat O2 sensors think the car is running rich so that the warm up stage doesn't spew as much unburned fuel while things are getting up to normal operating temp (at least that's what I've gathered the function to be, if anyone else can correct me, I'd like to know). "


dragonrage
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"The SAI is actually meant to warm and provide air for the catalytic converter. The rear O2 sensors help determine whether the system is working correctly or not."



High pitched straining noise? help? - AudiForums.com


hope that helps!

maarp

Thanks. That thread describes exactly what I'm hearing on a cold start. My wife was actually asking me last week what the high-pitched noise was when I started teh car.

I guess if the CEL keeps popping up, I'll have to look into it. As of today, all is well still.

K04-S4

SAI introduces additional ambient air into the exhaust system during the engine warm up phase while the ECU programming is intentionally running the engine rich. SAI does not trick O2's etc. The introduction of extra oxygen into the exhaust system permits the catalysts to minimize emissions while engine temporarily runs rich. Post Cat O2's on the B5's monitor health of front metal substrate cat(s) only and trip CEL if / when cat fails. Cats can fail early if SAI has not been working properly for a long period of time.

maarp

So does this mean I have a potential cat failure?

K04-S4

If SAI is broken and not repaired for some time then a premature cat failure is pending.

Ensure the SAI system is operating normally and not throwing recurring codes and your car will be fine.

maarp

Thanks for the help. Pretty much what my mechanic told me.

Audible B5

hey my car just had the Cel pop up the dreaded p0411.

just so im on the right page.. i heard that a faulty kombi valve can cause water build up in the secondary air pump due to leaking combustion gas condensating in the line.
my direction was to replace the kombi valve?
the SAI has already been replaced on the vehicle,but it is still throwing the codes.
if i check the line going from the kombi valve to the SAI and there is water in it? should i replace the kombi valve automatically or assume it could be something else?