Hi:
I've got a 1991 190E 2.6 (California car). I got a check engine light. I checked the code using the blinking light method and got a code 11 which I believe indicates an air injection system problem. I have checked the pump clutch by applying 12v. at the wiring connector and determined that the clutch works. What component turns the pump on / off? Where is it located?

Thanks

Steve

 

it is of course the engine control unit that actuates it.

the KE injection system control unit supplies a control signal to the air injection and transmission shift point retard relay. the air pump electro magnetic clutch and air pump switchover valve are actuated at the same time.

i think you know the purpose already.

 

What conditions does the ECU read that tells it to turn on the pump? Does the shift point retard relay control BOTH the transmission, pump and switchover valve? This sounds like it would likely be occuring during warmup since the engine will be running richer and could use the extra O2 to deal with higher HC levels and the transmission shifts later to speed the warmup process. If the pump doesn't come on then the O2 sensor will see a higher F/A ratio which combined with other sensor signals (coolant temp?) tells the ECU that the air injection is not taking place and produces the fault condition. Am I on the right track here?

If the shift point retard relay is what causes my transmission to shift at a higher rpm / speed when the engine is cold and that still happens then the relay is at least partly working. Is the air pump switchover valve electrically operated? Is it physically located in the plumbing between the pump and the manifold? Is its purpose to prevent exhaust gas from entering the pump when the pump is off? Where is the shift point retard relay located on this car?? With this information I think I can determine the problem and fix it.

Thanks

Steve