Emissions System

[oldandslowformula]

Did those procedures advise on which temperature sensor to check?



I assume that this is at the inlet to the air control valve? Did you ever check to confirm that the air control valve is actually operating, not stuck open or stuck closed? The description of the DTCs implies that the ECU monitors the air control solenoid valve ( which controls the air control valve); but, does not directly monitor the operation of the air control valve. If you have a hand vacuum pump you could apply it to the air control valve control line and then blow on the inlet to the valve to see if it opens and closes as you apply a vacuum.

Did some more testing yesterday and today. I first did a reset of the ECU by disconnecting battery to start fresh. Went for a drive, and again most of the monitors cleared fairly quickly. It took only 2 drive cycles and about 20-30 miles to notice that everything cleared again except for the secondary air monitor.

This morning I pulled the pipe again at the control valve. I connected an external air pump (air bed blower) to the control valve inlet and it doesn't seem like there is a control valve issue. I did a cold start and the valve seemed to open correctly by letting airflow through from the external pump, then when the secondary air pump turned off, it closed the valve where now restricted airflow from the external pump. The vacuum is cut off correctly by the solenoid (I checked the line) and there is no leaks backing out from the control valve inlet once the secondary air is not running. Then it threw a P0411 for "Secondary Air System Incorrect Flow".

So to me, this means the secondary air system is running fine. The solenoid, check valve, pump is operating as it should. I'm assuming it threw the code from getting a signal at the pump, no resistance. Something else is causing the monitoring system not to run...

 

[maximeskybase]

Try parking outside overnight if possible to get a real cold start
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[Old Guy]

Did some more testing yesterday and today. I first did a reset of the ECU by disconnecting battery to start fresh. Went for a drive, and again most of the monitors cleared fairly quickly. It took only 2 drive cycles and about 20-30 miles to notice that everything cleared again except for the secondary air monitor.

This morning I pulled the pipe again at the control valve. I connected an external air pump (air bed blower) to the control valve inlet and it doesn't seem like there is a control valve issue. I did a cold start and the valve seemed to open correctly by letting airflow through from the external pump, then when the secondary air pump turned off, it closed the valve where now restricted airflow from the external pump. The vacuum is cut off correctly by the solenoid (I checked the line) and there is no leaks backing out from the control valve inlet once the secondary air is not running. Then it threw a P0411 for "Secondary Air System Incorrect Flow".

So to me, this means the secondary air system is running fine. The solenoid, check valve, pump is operating as it should. I'm assuming it threw the code from getting a signal at the pump, no resistance. Something else is causing the monitoring system not to run...

Well that would seem to close the loop on everything working mechanically and confirms that the ECU is able to detect an air flow problem associated with the disconnected pump. Complete mystery as to why the monitor will not set. The last man standing does seem to be the ECU; but, that almost implies some kind of firmware problem which seems highly unlikely unless the monitor has never been able to set since day 1.