2007 Trailblazer w/ LL8 - P0418 - Secondary Air Injection (AIR) Pump Relay Control

[griffincox]

I can't believe that either a) a topic on this does not exist, or b) that I couldn't find it. Searched here and trailvoy.

Anyway, 2007 Trailblazer with LL8. 103,500 miles. In Denver where it just got down to 10-20° F.

Never had any issues up until this point. Now getting P0418. I can also here the pump or valve making way more noise than normal for the first ~30 seconds after startup.

I think the more popular code is P0410??? I only get P0418. Also, after clearing it comes right back. No more than 1 drive cycle required.

Any ideas? Clean or replace the silver thing on the passenger side of the motor? Sorry I haven't kept up. I owned a 2002 TB a while back and since then my energy has been spent on my 2008 AWD SS. Way more simple motor. Haha.

Any help is appreciated!

 

[The_Roadie]

Hilarious that the most recent thread on trailvoy was in April, and both responses included sneaky references to come over here.

Anyway, I think the reason there aren't many hits in a search is that it's a relatively new feature on relatively new vehicles and not many of them are failing.

The original SAIS like mine in 2004, just had a solenoid valve on the exhaust manifold to let the injected air in while the turbine pump was running. So many of there were getting jammed by exhaust gas crud buildup, and the system getting ineffective, that the EPA must have noticed and leaned on GM for a change. What they did was add a pressure sensor to the solenoid valve to confirm that the airflow from the pump was getting to the manifold. So my 2004 shop manual doesn't discuss this extra function, but I think I saw a schematic either here or elsewhere online. Your code is related to that pressure sensor or is a circuit inthe PCM that monitors the relay control for the solenoid valve.

I'd pull the hose off the solenoid valve first, and listen there on the next cold start. Make sure you can hear exhaust noises coming out of the valve, and that there's a lot of airflow out of the hose from the pump under the driver's seat. Depending on what you hear, then remove and clean the valve or replace it to get a new pressure sensor. Also inspect the wiring harness and connector carefully for abrasion or broken wires or a bent pin.

 

[griffincox]

To clarify, this is the system in question:

View attachment 31455

And the pump is GM 10373306 (#6), while the solenoid is GM 12619110 (#2). What exactly does this system do? What is it purging? Directly into the exhaust manifold? Is this part of the PCV system?

Thanks!

 

[The_Roadie]

That's it, the part numbers look right, and I *have* discussed the system's purpose 20-30 times over the years.

Mostly in threads containing "P0410".

Short answer: It's an EPA-mandated system that only started in 2003-2004 that blows filtered air in from the intake tube through a solenoid valve in the exhaust manifold that will react with unburned fuel that's being sent through the cylinders in "open loop" mode on a cold start. The system only actuates for 30 seconds, and the air pump sounds like a shop vac, and it draws 25-30 Amps! The purpose is to get the catalytic converter up to operating temp faster during start-up times, before you drive off and put a LOT more unburned fuel through the cat.

 

[The_Roadie]

Oh, and the I6 engine has no PCV. That's why the back side of the throttle body gets gunked up like a 200 year old spittoon and needs removal and cleaning every 30-50K.

 

[griffincox]

Great info roadie!

So it's just effectively mixing filtered air with overly rich exhaust gas. The pump probably has to be powerful to overcome the pressure from the exhaust manifold.

I will remove the hose first and then probably the solenoid. For cleaning or replacement.

I need to clean my throttle body too.

Out of curiosity, if no PCV, is there anything else in place to vent the crank case?

 

[griffincox]

Also, to add a little more fuel to the fire, here is the solenoid for 2006-2009 trucks. Probably the best price around. ACDelco 214-2151 Air Check Valve : Amazon.com : Automotive

 

[AtlWrk]

As Roadie mentioned there was an upgrade to the SAIS system around the 2006 year and the DTCs have changed a bit as a result. The P0410 of earlier years is now P0411 (SAIS incorrect airflow detected).

Fortunately GM has done a fairly remarkable job with electrical DTCs in that they are quite specific. For the later systems, P0418 points to an electrical fault in the pump relay control circuit:

Battery Positive---Ignition Switch---Fuse 54---Pump Relay Coil---C101---PCM

(C101 is the big connector mounted to the side of the under hood fuse block)

The fault could be an open, short, weak connection or failing component (the relay). Good news is this doesn't indicate a problem with the SAIS valve or pump.

(1) Check is fuse 54 "Air Sol" in the underhood fuse block.
(2) Disconnect the relay that's mounted to the pump on the frame under the driver's door and inspect for corrosion. Simply removing it and plugging it back in may clean it up enough to restore an iffy connection.
(3) The relay itself may be on it's way out.
(4) You can test the system by grounding the brown wire in C101 (terminal B7 in the middle of the connector) with the ignition in "Run"


Also, I believe Roadie meant that the 4.2Ls have no PCV valve. We do have a PCV system that uses a metered orifice in the head gasket instead of a valve. While this means there's no valve to replace, it also means there is nothing to trap the gunk before it gets to the intake and fouls up the the throttle plate.

 

[griffincox]

As Roadie mentioned there was an upgrade to the SAIS system around the 2006 year and the DTCs have changed a bit as a result. The P0410 of earlier years is now P0411 (SAIS incorrect airflow detected).

Fortunately GM has done a fairly remarkable job with electrical DTCs in that they are quite specific. For the later systems, P0418 points to an electrical fault in the pump relay control circuit:

Battery Positive---Ignition Switch---Fuse 54---Pump Relay Coil---C101---PCM

(C101 is the big connector mounted to the side of the under hood fuse block)

The fault could be an open, short, weak connection or failing component (the relay). Good news is this doesn't indicate a problem with the SAIS valve or pump.

(1) Check is fuse 54 "Air Sol" in the underhood fuse block.
(2) Disconnect the relay that's mounted to the pump on the frame under the driver's door and inspect for corrosion. Simply removing it and plugging it back in may clean it up enough to restore an iffy connection.
(3) The relay itself may be on it's way out.
(4) You can test the system by grounding the brown wire in C101 (terminal B7 in the middle of the connector) with the ignition in "Run"


Also, I believe Roadie meant that the 4.2Ls have no PCV valve. We do have a PCV system that uses a metered orifice in the head gasket instead of a valve. While this means there's no valve to replace, it also means there is nothing to trap the gunk before it gets to the intake and fouls up the the throttle plate.

Wow. If that code truly is narrowed down to that single circuit that is impressive.

I just checked fuse. It looks good. That was all I was up for tonight. Haha.

I'll have a look at the relay and test the circuit tomorrow.

After roadie mentioned the pcv or lack thereof I did a little research. It does have one of course. Unrelated to this system as stated. This is the first car I have owned with air injection though. So new concept. The rest of them have been big V8s. Haha. Emissions were at the bottom the concern list for those engines.

Seems like a simple system. Thanks for narrowing down the points of issue. Should be no problem to solve.

 

[griffincox]

Well. That was pretty easy to track down. It was damaged by driving over something. I think this must have happened a while back and the cold making the wiring brittle plus salt corroding it finally broke the conductors.

You would think GM would get the wiring above the fame rail...

All is well now. Soldered it back together with heat shrink tubing and taped it up and got it out of the way.

Thank you very much roadie and AtlWrk!