Air pump on a 99 Tahoe

[99whitehoe]

I tried using the search option but couldn't find what I was looking for so here goes.

My air pump constantly runs in my truck no matter if the motor is running or not. I have to take the positive battery cable off to make sure my battery does not run down. Someone said I should try to reset the air pump. How do I do that?

[SunlitComet]

:welcome:

You don't. The electric system is controlled by a relay that is triggered by the drivetrain computer(PCM). Your relay may be shorted out or your pcm might be faulty or is commanding it on all the time for a reason. At any rate the power feed to the pump thru relay control should be the AUX B Maxi fuse under the hood if you want to disable it until the primary problem is solved. Relay is in the same electrical box. Are you not showing any other problems or warning lights? Can you test your relay?




The electric motor Secondary Air Injection (AIR) system is used on the 5.7L to reduce Carbon Monoxide (CO) and Hydrocarbons (HC) .

The AIR system adds air (oxygen) to the exhaust manifold to continue oxidation after the exhaust gasses have left the combustion chamber. The heat from this reaction brings the catalytic converter (http://www.alldatadiy.com/alldata/AFI%7EV26446285%7EC33210%7ER0%7EOD%7EN/0/70910848/78153753/78154197/78154199/34853741/34857029/34857699/34856671) up to operating temperature taster when the engine is cold. This system consists of an electric AIR pump, check valves, and necessary plumbing.






An electric motor AIR pump (http://www.alldatadiy.com/alldata/AFI%7EV26446285%7EC33210%7ER0%7EOD%7EN/0/70910848/78153753/78154197/78154199/34853741/34857029/34857699/34872073) supplies filtered air from the air intake system to the AIR injection pipes.

The check valves, on the AIR injection pipes, prevent backflow of exhaust gasses in the AIR pump (http://www.alldatadiy.com/alldata/AFI%7EV26446285%7EC33210%7ER0%7EOD%7EN/0/70910848/78153753/78154197/78154199/34853741/34857029/34857699/34872073).

When the engine is started with a coolant temperature above approximately 15°C (45°F) or if the fuel system is in the Decel Mode, the VCM (http://www.alldatadiy.com/alldata/AFI%7EV26446285%7EC33210%7ER0%7EOD%7EN/0/70910848/78153753/78154197/78154199/34853741/34857029/34857030/101367125) energizes the AIR relay. The AIR relay then energizes the AIR clutch, which directs air into the exhaust manifold ports.

The control module (http://www.alldatadiy.com/alldata/AFI%7EV26446285%7EC33210%7ER0%7EOD%7EN/0/70910848/78153753/78154197/78154199/34853741/34857029/56218937/97115128) may turn the AIR pump (http://www.alldatadiy.com/alldata/AFI%7EV26446285%7EC33210%7ER0%7EOD%7EN/0/70910848/78153753/78154197/78154199/34853741/34857029/34857699/34872073) OFF when any of the following conditions occur:


The system is in the Closed Loop mode
Any DTCs are set
The system is in Power Enrichment mode for more than a short period of time
Low manifold pressure (over run)
Quick vacuum rise (rapid decel)

[99whitehoe]

Thanks for the info. I did have a blown fuse at first and replaced it and noticed the pump running constantly. I disconnected the positive terminal on the battery to look for pinched wires or anything obvious. Didn't see anything so I connected my positive and heard no noise. Thought it was funny but figured maybe it was a fluke thing and tried to fire it up. Nothing...fuel pump not coming on. Same fuse blown again. Took a spare and plugged it in and it blew it instantly. Took the fuel relay out and tapped it and put the fuse back in without the relay plugged back in. No blown fuse. Went to plug the relay back in assuming it would probably blow the fuse and it didn't.

Unplugged the relay and tried to start it up and it fired up. I couldnt figure out how the truck fired up with out the relay plugged in. Maybe something else shorted out?? Once I figure it out I'll post the results just in case someone else has this same issue in the future.

Sorry for the long post... Oh and thanks for the welcome!! Didn't find a newbie introduction section.

[SunlitComet]

which fuse was this that was blowing. How did you get to the fuel pump relay from the air pump relay. Maybe I missed something here.

BTW we users make your first thread or post the introduction section usually.

Don't fret over long posts the more info the better.

[99whitehoe]

Well when I noticed the air pump staying on all the time I also noticed the fuel pump itself sounded like it never would shut off. So I disconnected the battery too look for something obvious which I didn't see. I went to hook the batt back up and now had nothing. No air pump making noise no fuel pump....nothing. So I began to look around at different things like fuses and noticed the fuel pump fuse(red 30 amp) was blown. Once I saw that then I got to thinking that maybe the fuel pump relay was stuck causing the air pump to run constantly. So I unplugged the relay for the fuel pump assuming that the fuel pump would not come on and if my assumption was correct neither would the air pump. Unplugged the relay and turned on the key and the fuel pump and air pump came on just like before..even with the fuel pump relay not installed. Then I plugged the relay back in thinking that the fuse that had previously blew would do it again. Well it didn't. I'm gonna pull the distributor to see if any wires behind the motor may be shorted or something. If not I guess I'll take it to a shop since I'm out of ideas.. Some reason I'm thinking I have a wire broke or shorted out. Gonna be something simple I know!

[SunlitComet]

I would check underneath the engine bay fuse/relay box for a broken circuit

[99whitehoe]

Found what the problem was. I had an O2 sensor wire shorted to my oil sending unit wires.. Don't ask me how they got together but thats what it was. I cut them and rewired it and everything seems to be good to go.

[msark]

I just bought a 97 Tahoe. Inspecting it today and found that my A.I.R. relay is not installed.... Do I need to put it in?? Also found the Brake Lamp Relay missing as well as the 30A Stop Hazard fuse... Help??