355 Secondary Air Pump Wiring Check (5.2)

I've noticed that it's difficult to tell if your secondary air pump is running above all the other noises in the engine bay. The pump only runs when the engine is running and the coolant temperature is low. However, thanks to an accidentally discovery by @Bertocchi , you can hear the pump operating with just the key turned on if you pull the injector relay in the passenger footwell.

This should also check all the wiring from the Motronic ECU to the secondary air relay and the wiring from the relay to the secondary air pump.

Somehow by pulling the injector relay, the Motronic ECU goes into some kind of default mode and turns on the secondary air system (including sending a signal to the secondary air solenoid valve). Unfortunately, without vacuum from the engine, it won't test the solenoid valve or the secondary air valve.

This is applicable to the 5.2 engine. It may or may not work if you pull the injector relay for the RH bank on the 2.7 car.

Just wondering what other systems are turned on by doing this.

 

Maybe some pumps are noisier than others ..... or some engines are noisier than others ... or some folks like me are just deaf

 

Here's another interesting recent observation. The 5.2 has a fuel pump priming circuit when you turn on the key. The pump runs for 4~5 seconds when the ECU commands it on. However, if you cycle the ignition key, the pump won't run again until you actually start the car. After running my car for 30 seconds today, I pulled the fuel pump relay and put a test light across the relay socket (coil pins). When I turned on the ignition, the test light only illuminated for a second. Subsequent cyclings of the ignition key didn't illuminate the light again.

It's like the ECU is estimating the pressure in the rail (even though there is no pressure sensor).

 

My IAC seems to be noisier than my secondary air pump.