P0410 Olds Silhouette Strange voltage readings at air pump and vacuum solenoid

My 2000 Silhouette has a P0410 "Secondary Air Injection System" DTC. I replaced pump, and one of the diverter valves that did not hold vacuum. Still have the DTC. Strangely, I took some voltage readings at the pump and noticed it reads like 5 volts or so with Key Off Engine Off. Then, with Key On Engine Off, it read like 11.98 volts, and then with Engine running it dropped back to about 5 volts. Pump does not come on. I also took some voltage measurements at the vacuum solenoid, and did not get any voltage on any of the three wires with key off, but got like 5 volts on one of the wires with key on engine off. Also, when you start the engine, there is no vacuum present in the lines going to the diverter valves. Both related fuses appear fine....

Darn emissions stuff, but I need to pass inspection this month, which I cannot do with the "service engine" light on the dash.
Any ideas? Thank you so much!

That doesn't make sense.....

The air pump should have no voltage to it, until the air pump relay is grounded by the PCM, and then it should get BAT voltage.....

The air pump is not commanded to run all the time, on start up(start up is the only time the pump runs).......that is determined by coolant temp......on a cold engine, the pump will be commanded on and the diverter valve opened, and like I said, run time is predetermined by coolant temp.....so if coolant temp is 32 degrees, run time will be long......40 degrees less time....50 degrees even lesser.......a car that has reached normal operating temp, and is shut off, will have a high coolant temp....and if restarted within minutes, the air pump will not even be commanded on by the PCM.....

Thanks for the reply. I don't think the air pump comes on at all. It's July in New Jersey, temps in the 80's. The car sat all night. Is 80 too warm for the ECM to call for secondary air injection? Could the temp sending unit be bad? It seems to be working fine based on the dash board temp gauge? again, thank you.

I am not exactly sure at what min coolant temp, an air pump will be commanded on.....

However, I would think, that on a cold engine, first thing in the morning, it would be commanded on(the duration will be determined by coolant temp).......but if that code is set, it will not come on.

The code will have to be cleared......you have to realize, that that code is set, when the PCM does not see a lean condition in the exhaust on startup.....

Normally, it will see a rich condition on startup......but because the pump is blowing air through the solenoid valve into the exhaust, the O2 sensor will see this oxygen, and give a lean reading, so the PCM knows the air pump AND the solenoid valve is working......for example, the pump may run, but if the solenoid valve does not open, the O2 sensor will not sense the oxygen in the exhaust, and the code is set....

There is something wrong if you are reading 5 volts to the air pump....

Thank you again for the input. I verified that the air pump is good by taking 12 volts directly to it. It runs. Both check valves are good, as they both hold vacuum. I cleared the codes from the computer, and then started the engine. The air pump did not come on, nor do I feel any vacuum being applied to the check valves. I verified that all fuses under the hood are good. I wonder if there is a relay somewhere for this secondary air system? I do not see any relays under the hood labeled as such....

Unfortunately, I can't find schematics for this....

I was able to find some information, including a schematic. But no one seemed able to tell me where under the hood to find the air pump relay. Finally, I found it. I had to remove the passenger side front wheel, and then remove part of the plastic wheel well, and there was the relay hidden behind the front fender. That is the exact opposite location of the air pump itself, which is behind the front fender on the driver's side! The relay was visibly burnt up and corroded. I replaced it, erased the codes, and started the car. The air pump ran for the usual 30 seconds or so, and then cut off, as it should. So, hopefully, this issue is resolved. If not, well, I'll keep posting on this forum! Thanks. (I tried to attach the schematic, but can't seem to figure out how....)

Good job on finding that relay.......a bad relay contact would explain you getting 5 volts, instead of 12 volts to the air pump....

Strangely, the mystery continues....
Still throwing P0410. The air pump runs for about a minute as expected on cold start-ups. But not always.
My wife tried to tell me the other day that the air pump was running for no apparent reason during normal driving. I explained that she must be mistaken, as it doesn't work that way, but only runs on a cold start-up. But yesterday, I experienced this myself, as I heard the air pump run two or three times in short bursts for no apparent reason in a completely warmed up engine. Some kind of gremlins, I guess. Additionally, and possibly unrelated....The other day I turned off the engine, exited the vehicle, and went inside the house. I heard the car horn beep, and then I went outside to see the turn signals flashing dimly. Weird! I inserted the key in the ignition, turned it to run, and then off again. The weird behavior ceased. Gremlins, I say....

Update. I decided to try to take a look at the vacuum solenoid and make sure it was working properly....While accessing it, I realized that I had failed to connect one of the two vacuum lines last time I was working on the car....(In my defense, the thing is really buried behind the engine and hard to see)....As a result, the air pump was working, but the check valves were not opening, and hence, the P0410 trouble code continued. The solenoid checked out okay, and with the vacuum lines properly connected, the code is gone and seems to be working just fine....

Last month I had to replace one of the coolant 'T' fittings behind the engine that supply the heater cores. I bumped the vacuum line off the air valve and got the 410 code as well as a rough idle when the air pump was running. Scratched my head for a while until I remembered those vacuum lines on the valves! Good job finding that relay--its down there where water from the radiator cap can fall on it if the overflow tube leaks or you have the cap off. Not a great spot, but near the battery I suppose.

Hi!
Secondary pump relay is located under the wing, front, right