Secondary Air Pump Operation
 

Most likely the forum has discussed this but I cannot find an answer to my specific question.

Does anyone know the trigger points for when the secondary air pump operates or not?

My understanding is the pump turns on and runs for a minute or so when two conditions are met: 1) the engine is cold and 2) the outside air temperature is below a certain value. Is this true?

Does the pump have to meet both conditions at the same time or is one enough? My pump runs whenever the engine is started cold regardless of the outside temperature.

Thanks

Not sure about your car as you didn't specify model year. On the newer cars (987), input signals for the SAI pump to run include coolant temp, intake air temp, altitude, and if the front O2 sensor is operating to allow closed-loop operation. All these values are part of the algorithm the DME uses and when it figures out when and how long the pump should run.

Regards,
paul...

My car is a 2001 S. The O2 sensors are brand new.

Bentley doesn't go into any other detail about the SAI operation, but it seems to be tied to when the engine is started and it's below normal operating temperature, and runs for approximately 60 seconds. And it doesn't seem to care what the outside air temperature is.