SwayBar

Nothing measures the air flow in the SAI ports themselves.

If any number of SAI ports are clogged, proportionately less air will flow into the exhaust system, thus less air will be sensed by the O2 sensor in that bank of cylinders.

mlucas70

Aha, so potentially an SAI fault code like P0410, in theory, could actually be triggered by a dirty O2 sensor, but as the sensor is 'working', albeit badly, you dont get an error code for the 02 sensor itself.
Having changed the Check Valve, next job will be the O2 sensors to see if that makes a difference to getting the CEL.
Will try everything before a flush and top end job.

SwayBar

Along those lines, you can swap the existing O2 sensors with one another and reset the codes; if the next error occurs on the other bank, then it is a weak/faulty O2 sensor. Boy, wouldn't that be great!

Gary Perry

The original bypass solution also included a replacement of one 02 sensor because the Hammer codes indicated there was a problem on the passenger side exhaust with one of those sensors.

99three

Bump. Just wondering if anyone has additional insight on this topic.

Gary Perry

Turns out the vacuum canister is cracked and has to be ordered from Germany. The car will be down for a week waiting for the part to arrive.

99three

Can you give more info on this canister and where it's located.

Gary Perry

The reservoir is in the left rear wheelwell behind the plastic liner. Part number 993 110 060 00

cdmdriver

So let me get this straight.. If you are getting both 1411 and 0410 SAI related codes, the problem could be a cracked vacuum canister or vacuum line. I will have to check that out.

flatsixforme

That could potentially save some people A LOT of money!

hoggel

The SAI check is a cycle. Here's some blah blah I posted in a previous thread.

On cold start the secondary air pump is turned on by the ECU. The ECU also sends a signal to open a vacuum control valve that operates a vacuum valve allowing the secondary air into the plumbing. The secondary air is injected into the exhaust before the pre cat O2 sensor.

The ECU monitors the pre cat O2 sensor. It is a closed loop control system that adjusts the air fuel mixture to make the engine operate as close to the stoichiometric point as possible.

On cold start the fresh air from the secondary air pump creates a very lean condition at the pre cat O2 sensor. The ECU compensates by injecting more fuel resulting in a fuel rich condition in the exhaust from the head. That unburned fuel in the exhaust combines with the oxygen from the SAI system and burns thereby heating the catalyst up to operating temperature.

In an OBDII car the ECU checks for the presence of the pump. On cold start the ECU checks that the O2 sensor signal goes through the stoichiometric, lean, rich, stoichiometric cycle with the SAI.

mlucas70

I dont see how the vacuum reservoir from the throttle (993 110 060 00) can have any bearing on the SAI or the codes its can throw.... the SAI takes its air from the hole in the lower left side of the air filter...
Any follow up Gary ??

Cheers
Martin

ReinerFink

If your vaccume canister is cracked, then this valve won't open, and the air cannot flow through the SAI port.

-reiner