I noticed the other day that when I start the car(first time) that the SAI is only kicking on intermittently. One morning it will come on, another it won't. It has been pretty cold here in the North East US, so I am wondering if the SAI kicks on only when it is warmer out, say above 40*.
Any thoughts?

 

Mine kicked on at 25* this morning.

 

Maybe a bad coolant temp sensor or connector?


From RAVE: " "The engine control module (ECM) checks the engine coolant temperature when the engine is started, and if it is below
60º C (131F), the SAI pump is started. Secondary air injection will remain operational for a period controlled by the
ECM (76 seconds for NAS vehicles, 64 seconds for EU-3 vehicles). The SAI pump operation can be cut short due to
excessive engine speed or load."

 

i'll have to check them, I think coolant temp sensor is OK because the numbers on my ultra gauge seem to be normal.

 

I'm not sure how it is "supposed" to work, but mine only comes on intermittently as well. When it is REALLY cold, it doesn't come on. But then again, I think mines a little messed up, because sometimes even after I have been driving a while, it will come on while I stopped at a light or something.

 

The function of SAI is to add oxygen to the exhaust to make the reaction in the catalytic converters more complete when they are cold. Once the converters get hot, they are more effective and the exhaust is much cleaner. Gasoline engines pollute more after startup than they do for the rest of the time they are running so this system helps alleviate that. The blower should kick on and operate every time the engine starts cold.

 

I checked the connections and they seem fine. Does anyone know which fuse the SAI is associated with? Is it possible that since there is an association between the SAI and the O2 sensors would this be an indicator it is time to replace the O2 sensors? I know that with 104K on the car they are probably due anyway, but since it is so friggin' cold here I have just put it off.

 

I'm not a ton of help here, but it looks like fuse 2 under hood box. Check the relay too.


RAVE:




Secondary air injection system




When the engine is started, the engine control module checks the engine coolant temperature and if it is below 55






C, the ECM grounds the electrical connection to the coil of the secondary air injection (SAI) pump relay.


A 12V battery supply is fed to the inertia switch via fuse 13 in the engine compartment fusebox. When the inertia


switch contacts are closed, the feed passes through the switch and is connected to the coil of the Main relay. An earth


connection from the Main relay coil is connected to the ECM. When the ECM completes the earth path, the coil


energises and closes the contacts of the Main relay.


The Main and Secondary Air Injection (SAI) pump relays are located in the engine compartment fusebox. When the


contacts of the Main relay are closed, a 12V battery supply is fed to the coil of the SAI pump relay. An earth connection


from the coil of the SAI pump relay is connected to the ECM. When the ECM completes the earth path, the coil


energises and closes the contacts of the SAI pump relay to supply 12V to the SAI pump via fusible link 2 in the engine


compartment fusebox. The SAI pump starts to operate, and will continue to do so until the ECM switches off the earth


connection to the coil of the SAI pump relay.


The SAI pump remains operational for a period determined by the ECM and depends on the starting temperature of


the engine, or for a maximum operation period determined by the ECM if the target engine coolant temperature has


not been reached in the usual time.


When the contacts of the main relay are closed, a 12V battery supply is fed to the SAI solenoid valve via Fuse 2 in


the engine compartment fusebox.


The ECM grounds the electrical connection to the SAI vacuum solenoid valve at the same time as it switches on the


SAI pump motor. When the SAI vacuum solenoid valve is energised, a vacuum is provided to the operation control


ports on both of the vacuum operated SAI control valves at the exhaust manifolds. The control vacuum is sourced


from the intake manifold depression and routed to the SAI control valves via a vacuum reservoir and the SAI vacuum


solenoid valve.


The vacuum reservoir is included in the vacuum supply circuit to prevent vacuum fluctuations caused by changes in


the intake manifold depression affecting the operation of the SAI control valves.


When a vacuum is applied to the control ports of the SAI control valves, the valves open to allow pressurised air from


the SAI pump to pass through to the exhaust ports in the cylinder heads for combustion.


When the ECM has determined that the SAI pump has operated for the desired duration, it switches off the earth paths


to the SAI pump relay and the SAI vacuum solenoid valve. With the SAI vacuum solenoid valve de-energised, the


valve closes, cutting off the vacuum supply to the SAI control valves. The SAI control valves close immediately and


completely to prevent any further pressurised air from the SAI pump entering the exhaust manifolds.


The engine coolant temperature sensor incurs a time lag in respect of detecting a change in temperature and the SAI


pump automatically enters a 'soak period' between operations to prevent the SAI pump overheating. The ECM also


compares the switch off and start up temperatures, to determine whether it is necessary to operate the SAI pump.


This prevents the pump running repeatedly and overheating on repeat starts.


Other factors which may prevent or stop SAI pump operation include the prevailing engine speed / load conditions.

 

The SAI solenoid is a common failure point and a cheap fix.

 

I just found this little gem in the RAVE for those who care:
The ECM checks the engine coolant temperature when the engine is started in addition to the elapsed time since the
engine was last started. The engine coolant temperature must be below 55°C (131°F) for the SAI pump to run.

NOTE: The ambient air temperature must also be above 8°C (46°F) for the SAI pump to run.
One this it has not been here in the Northeast lately is above 46*
This explains things a little, but bballjames said his was coming on randomly.