Secondary Air Diagnosis

[insite]

my car is throwing some codes on secondary air issues. working on diagnostics; i have diagrams, etc.

one thing i haven't ever seen is a SIMPLE description of the logic behind the system, i.e. how EXACTLY does it work and what EXACTLY does the triggering?

for instance, under what conditions is the pump triggered? i know it's supposed to be cold start, but what sensors does it look at to get a 'start' or 'no start' condition? does it generally come on IMMEDIATELY when the car is started, or is there some delay?

under what conditions will it turn off? what sensors are monitored to make this decision?

basically, the only diagnostic checklists for this system that i've seen are pretty poor IMO. i think that if i knew exactly how the system was SUPPOSED to work, i could design a better diagnostic plan before i dive in. any help is greatly appreciated.

[Loren]

my car is throwing some codes on secondary air issues. working on diagnostics; i have diagrams, etc.

one thing i haven't ever seen is a SIMPLE description of the logic behind the system, i.e. how EXACTLY does it work and what EXACTLY does the triggering?

for instance, under what conditions is the pump triggered? i know it's supposed to be cold start, but what sensors does it look at to get a 'start' or 'no start' condition? does it generally come on IMMEDIATELY when the car is started, or is there some delay?

under what conditions will it turn off? what sensors are monitored to make this decision?

basically, the only diagnostic checklists for this system that i've seen are pretty poor IMO. i think that if i knew exactly how the system was SUPPOSED to work, i could design a better diagnostic plan before i dive in. any help is greatly appreciated.

I sent you a PM with some information.

[pk2]

Sounds like a great Idea. You might see if you can get some fundamental layout diagrams. Bosch used to publish such. How tight Porshe keeps the lid on the details of there adaptation of the motronic I don't know. Actually, thinks there still are somewhat generic Bosh manuals.

Regards, PK

Edited February 16, 2009 by pk2

[Loren]

Sounds like a great Idea. You might see if you can get some fundamental layout diagrams. Bosch used to publish such. How tight Porshe keeps the lid on the details of there adaptation of the motronic I don't know. Actually, thinks there still are somewhat generic Bosh manuals.

Regards, PK

I have added the Bosch tech book here.