Secondary Injection Pump

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Dec 9, 2004 | 10:04 AM

RWLib3

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Secondary Injection Pump

How can I test the Secondary Injection Pump? VAG-COM? I keep getting a CEL stating insufficent flow. Had it worked on and a pipe was loose, so now I dont get the hissing on cold startup, but still get the code?!?

TIA

Dec 9, 2004 | 10:16 AM

DashingMax

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Hissing on cold startup is...

...something you SHOULD hear. When the car is cold, the secondary air pump pushes extra air (oxygen) through the exhaust system. This is because the catalytic converters are cold and cannot clean all bad exhaust air.

The air pump dilutes the air during the initial minute or so, while the cats are warming up.

This pump is triggered by selenoid, which in turn is triggered by your vaccum line. These vaccumm lines rupture frequently & the air pump never turns on...triggering the CEL.

Double check that "loose pipe" again. Check all vaccum lines to and from the air pump selenoid.

Good luck.

Dec 9, 2004 | 11:17 AM

Non-Audi Tom

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Re: Hissing on cold startup is...

Also check to ensure the casing on the pump itself hasn't split. On my former car (New Beetle w/ 1.8t several rivets had failed and the case was splitting so it was pumping some air out to atmosphere vs to the exhaust. I presume the pumps are all the same.

I just replaced rivets with small screws/ lock nuts. Another person simply used zip strips since it's a plastic housing and that worked fine too.

Dec 9, 2004 | 11:26 AM

RWLib3

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Re: Hissing on cold startup is...

I know...but when the pipe was loose it was MUCH louder than it is now..so I know its not that pipe again.

Dec 9, 2004 | 04:34 PM

A6Gary

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From: Lake Tapps, WA

The Secondary Air Injection pump runs for 100 secs on cold start-up. You can test it using the...

output diagnostic test mode (DTM) of VAG-COM (Function 03 under "Engine"). The pump is activated by a solenoid (activated by the ECU). The combination valve, which mixes the pump air into the exhaust, is activated by vacuum that is triggered by a solenoid valve that opens a vacuum circuit to the combination valve. Which VAG Code number are you getting? Insufficient flow could mean a bad MAF. Some other VAG Codes that may apply to the secondary air injection system are:

17536: Bank1, System too lean
17538: Bank2, System too lean
17822: Sec Air Inj Sys, Bank2 Leak Detected
17832: Sec Air Inj Sys, Bank1 Leak Detected

Without knowing which VAG Code the CEL is showing, your problem could be one or more of several items.