Two Engine Codes.

Mossyoakglock · November 26, 2009

I tried posting this in the SUV forum but I never got an responses and figured that these codes are universal to all GM vehicles.

Our 06 Envoy had the check engine light come on and threw two codes. They are P2431 (Secondary air injection system pump stuck on and P2444 (secondary air injection system pressue senor signal performance fault).

The problems that Autozone showed in their system are either a failed air pressure sensor or open or short circuit condition on the air pressure sensor circuit.

Is it a sensor that is bad? What are other probable causes and fixes for this issue? The car runs great with no signs of anything wrong. It will go off for a day or two and then come back on for a day and then go off.

I have read that the canister pictured can be the cause of it, but I'm not sure what exactly it is. What is it and could this be the cause?

Thanks.

minibike132 · November 26, 2009

I tried posting this in the SUV forum but I never got an responses and figured that these codes are universal to all GM vehicles.

Our 06 Envoy had the check engine light come on and threw two codes. They are P2431 (Secondary air injection system pump stuck on and P2444 (secondary air injection system pressue senor signal performance fault).

The problems that Autozone showed in their system are either a failed air pressure sensor or open or short circuit condition on the air pressure sensor circuit.

Is it a sensor that is bad? What are other probable causes and fixes for this issue? The car runs great with no signs of anything wrong. It will go off for a day or two and then come back on for a day and then go off.

I have read that the canister pictured can be the cause of it, but I'm not sure what exactly it is. What is it and could this be the cause?

Thanks.

Sorry, I did not see your response in the other thread after I last posted in it. You will not notice any difference in running, fuel mileage etc. other then the light.

The secondary air injection system is designed to reduce emissions during cold starts by injecting fresh air into the exhaust to heat up the catalyst to operating temp faster. The picture is of the actual pump.

On a cold start the pump should run anywhere from a few seconds to a few minutes. You can check to see that it turns on (which I'm sure it is given the codes) and that it turns off in a few minutes. You can follow the tube up into the engine compartment to the valve which is mounted above the exhaust manifold just below the air intake. When the pump is on air should be blowing out of the tube that goes into the valve, if not there is a restriction in the tube (I'm sure there is no restriction, again given the codes you have).

When the pump turns on the valve should also open to allow that air into the exhaust, if it either does not open or is open all of the time one or both of those codes may set.

On to what could your problem be. This isn't an overly complex system and neither is the diagnostics, if you have a bi-directional scan tool capable of controlling the system which you do not. It is not something that is always on or always off or that you can make turn on and off without some expensive tools. The other problem is that just about every part of this system is something that gets replaced on many vehicles so I can't say "it's usually this".

You can check to see that the pump turns on and off withinn a few minutes of a cold start. If it does then we can forget about the motor, the relay, and the wiring to the pump. If it doesn't turn on then you could check some fuses, other wise you would need to be able to command the system on for testing. If it never turns off there is a short to voltage somewhere and we could track that down.

If it works fine you can disconnect the tube going into the valve during a cold start and if you have flow in but not out it is most likely a valve. Valves are very common, the electrical circuits controlling it are not common issues.

That all sounded clear coming out of my head but I know sometimes I can get confusing, let me know if you have any questions.

Mossyoakglock · November 26, 2009

It was a little confusing but I think I got the most of it. Tell me if I'm right or wrong with this...basically, in the morning when I go to start it, get by the pump and see if it comes on, stays on, or doesn't come on at all. After that, track down the hose from the pump to the engine compartment and remove the tube from the valve and see if the valve opens and if it is either sucking or blowing air.

So, am I correct on the procedure and what to look for?

minibike132 · November 26, 2009

It was a little confusing but I think I got the most of it. Tell me if I'm right or wrong with this...basically, in the morning when I go to start it, get by the pump and see if it comes on, stays on, or doesn't come on at all. After that, track down the hose from the pump to the engine compartment and remove the tube from the valve and see if the valve opens and if it is either sucking or blowing air.

So, am I correct on the procedure and what to look for?

Yes but I would track down and disconnect the hose from the valve before starting it. That way you can verify that the pump turns on and pushes air to the valve before the pump shuts off, it may only run for 10 seconds.

Mossyoakglock · November 27, 2009

I disconnected the hose and had my sister start it. I heard the pump turn on, at least I think it was the pump. It made a raspy noise and air was being sucked in the tube. She cut the car off to soon and when I had her restart the car it didn't do it again. I also found a big gray fuse in the engine fuse box, number 54 or 55 which is the Air Injection Reactor Solenoid. Could that be the problem? I checked all the other fuses and they were all good.

I'm going to let the car sit for about another hour and have her restart it and let it run and see when the pump shuts off. Could it be the fuse, or what else could it be?

minibike132 · November 28, 2009

I disconnected the hose and had my sister start it. I heard the pump turn on, at least I think it was the pump. It made a raspy noise and air was being sucked in the tube. She cut the car off to soon and when I had her restart the car it didn't do it again. I also found a big gray fuse in the engine fuse box, number 54 or 55 which is the Air Injection Reactor Solenoid. Could that be the problem? I checked all the other fuses and they were all good.

I'm going to let the car sit for about another hour and have her restart it and let it run and see when the pump shuts off. Could it be the fuse, or what else could it be?

If the pump runs the fuses are fine. An hour may not be enough, I would try it after sitting overnight.

Mossyoakglock · December 6, 2009

I tested the pump and it runs and blows air for about 10-15 seconds and then shuts off. So I'm guessing that the problem is at the valve/solenoid. Can those usually be purchased at any autoparts store, or maybe rockauto.com?

Is it the valve?

VRSCA1 · December 8, 2009

I tested the pump and it runs and blows air for about 10-15 seconds and then shuts off. So I'm guessing that the problem is at the valve/solenoid. Can those usually be purchased at any autoparts store, or maybe rockauto.com?

Is it the valve?

Check for water intrusion into the relay and connector near the air pump under the vehicle,if dry so signs of water replace the solenoid up top under the hood follow the hose from the pump to the solenoid,sometimes you find water in the solenoid water/moisture from exhaust ruins solenoid rusted/corroded shut.

When the pump comes on the PCM monitors the o2 sensor for a change expects to see voltage low under 400 millivolts generally speaking if not MIL light on thinks the pump is inoperative but the solenoid/check valve is inoperative in a nut shell.

So check the relay near the air pump for water intrusion if dry and pump works,put a solenoid/check valve on.

Mossyoakglock · December 8, 2009

I'm guessing the relay is dry since the pump is working. I might take the check valve off and clean it and see if there is anything siezing it up and see if that works before dropping the money on it. Funds are tight right now, especially with the holidays.