Secondary Air System Monitor Incomplete!

[blue62]

Originally Posted by piper6909

I think SAI test happens at idle. Did you let it idle for at least 2-1/2 minutes?

It only does the EVAP test if your fuel tank is between 1/4 and 3/4 full, so check your fuel level.

My current understanding of the SAI test is that it happens in closed loop. When the ECU decides it is ready to test the SAI it turns on the air pump while in closed loop. the ECU then looks for a voltage drop to .200 millivolts at the pre cat o2 sensor within 2 seconds. This voltage drop is conformation to the ECU of the correct excess o2 in the exhaust in the correct time frame Thus the SAI is working properly.
If the ECU fails to see those changes it throws a SAI related code.

The SAI function in open loop at start up is to help the cats warm up faster and help burn off hydrocarbons.

This is my current understanding of how the SAI works and how the ECU tests it.

I have not researched the EVAP system yet so my understanding of it is damn little.

[piper6909]

Originally Posted by blue62

My current understanding of the SAI test is that it happens in closed loop. When the ECU decides it is ready to test the SAI it turns on the air pump while in closed loop. the ECU then looks for a voltage drop to .200 millivolts at the pre cat o2 sensor within 2 seconds. This voltage drop is conformation to the ECU of the correct excess o2 in the exhaust in the correct time frame Thus the SAI is working properly.
If the ECU fails to see those changes it throws a SAI related code.

The SAI function in open loop at start up is to help the cats warm up faster and help burn off hydrocarbons.

Good information to keep in the memory bank. Thanks.

So, in that case maybe Speedyspaghetti should let it run a few minutes for it go into closed loop, and THEN let it idle for 2-1/2 minutes to do the SAI test?

[blue62]

Originally Posted by piper6909

Good information to keep in the memory bank. Thanks.

So, in that case maybe Speedyspaghetti should let it run a few minutes for it go into closed loop, and THEN let it idle for 2-1/2 minutes to do the SAI test?

I am not sure what conditions have to be met before the ECU "decides" to test SAI readiness or operation.
I just know from research "how" the ECU tests SAI readiness or operation.

The more research I do on how OBDII is set up, how various sensors actually work, how the sensors are related to each other and OBDII as a complete system the more interesting it becomes.
I also find out I know less and less. LOL
Certain information on OBDII (probably more correct to say ECU operation) is difficult to find.