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Re: Service light came on, connected a scanner and got
There won't be - the secondary air injection system is strictly for cold-start emissions. You won't see any effects in driving, but if you have any sort of emissions check in your state's inspection, you will fail.
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CODE PO411 - SECONDARY AIR SYSTEM INCORRECT UPSTREAM FLOW DETECTED. POSSIBLE CAUSES, AIR PUMP OUTPUT IS BLOCKED, AIR BYPASS SOLENOID LEAKING OR BLOCKED, AIR BYPASS SOLENOID IS STUCK OPEN OR STUCK CLOSED. AIR INJECTION PUMP HOSES LEAKING, PCM HAS FAILED.
CODE PO411 SECONDARY AIR SYSTEM INCORRECT UPSTREAM FLOW DETECTED.POSSIBLE CAUSE / AIR PUMP OUT PUT IS BLOCKED./ AIR BYPASS SOLENOID LEAKING OR BLOCKED./AIR BYPASS SOLENOID IS STUCK OPEN OR STUCK CLOSED./ AIR PUMP INJECTION PUMP HOSES LEAKING. / OR PCM HAS FAILED.
Funny that they changed the temp guage sensor....known problem on pre-2001 Audi TT and VW engines. Maybe yours was an early build 2002, so they helped you avoid a future problem.
As for the air flow, another known problem is the MAF (mass airflow) sensor. Don't panic, as this is a do it yourself job. Very likely problem if you ever installed a K&N type aftermarket air filter. These oiled filters cause buildup on the sensor. Free fix is to take the sensor body off (its the big ring/pipe coming off the air filter box before the rubber air intake hose) and clean the senor with isopropyl alcohol. Sensor body comes off by loosening the hose clamp on one end, and two screws into the filter box on the other. Don't forget to release the wiring harness plug by gently releasing the tab with a flat head screwdriver.
If your not comfortable with the cleaning, just find the MAF part on-line...about $200 bucks for a new one from Bosch. Very easy to do it yourself and a common failure point on the Audi.
For those still having the coolant sensor problem, also easy to replace yourself....about $10 bucks with a new o-ring.
Like GURU said, a code reader tool will tell if you have these problems, after the engine light comes on.
Secondary AIR System Incorrect Upstream Flow Detected Possible cause: Electric air injection pump hoses leaking Air pump blocked AIR bypass solenoid leaking or blocked AIR bypass solenoid stuck open or stuck closed