2002 GMC Envoy exhaust leak

[Wano]

Does anyone know what this plate is ? It has a crack in it and my Envoy failed visual inspection at smog station. Smog report also says OBDII monitors "not ready" and "oxygen sensor" is listed.
Location is passenger side. Thanks for any help you can provide.

 

[Mooseman]

That is the SAIS block off plate. This was before the SAIS was installed at the factory so it is legal for you. Part numbers are here:

eBay Listing - Air Check Valve delete parts: GM 2574378 & GM 24577193

These are used when deleting the Air Pump Check Valve, which is part of the SAIS: Air Check Valve: ------------------------------------------------------------------------------------------ Check Valve Gasket - GM 24577193 & AC Delco 219-351: -$4.94 - Free Shipping...

gmtnation.com

As you can see they did improve that part.

An alternative if the part is NLA is to make one yourself with some plating or get one from a pick-n-pull yard. The gasket should still be available for later years that do have the SAIS.

 

[Wano]

Man you guys are great and this site is just wonderful. So glad I found it.
Much thanks. I really appreciate your help. I feel better already.
Will be on the quest to find this part first thing in the morning.

 

[c good]

My 2002 Envoy does not have this at all. No check valve or even a place for a check valve. I wonder why his 2002 is different? Mine is a 50 state model. USA.

 

[Wano]

I went to the GMC dealer here today and the plate is no longer available. I checked the links that were posted here and no luck. I also checked various sites for GM parts and nope. I don't have the tools to machine the plate or make one.
This is a rebuild from Jasper in Texas. 38K on the rebuild and this is the first year it didn't pass smog.
AutoZone has the gasket for $16, but that plate is tough to find. .... and I'm still hoping that when I do replace this plate then the 02 sensor "not ready" will go away and the smog test will get past that point.

 

[budwich]

can you remove the plate? IF so, get a tube of "muffler cement" and make a "patch" over the crack. Make sure that the patch is total hardened before putting is back on.

 

[Mathoran]

https://www.gmpartsdirect.com/oem-parts/gm-secondary-air-injection-pipe-cover-12574378

12574378 - Genuine GM Cover, Secondary Air Injection Pipe

GMPartsGiant.com offers the great deal for genuine GM parts, 12574378. Cover, Secondary Air Injection Pipe for $4.89. All parts are backed by the GM's warranty.

www.gmpartsgiant.com

Aren't these the right part?

 

[Mooseman]

My 2002 Envoy does not have this at all. No check valve or even a place for a check valve. I wonder why his 2002 is different? Mine is a 50 state model. USA.

My 02 did have one (I kept the block off plate from it and is currently on my 07). Maybe yours was an early production model that didn't have it but my 02 definitely did have it.

can you remove the plate? IF so, get a tube of "muffler cement" and make of "patch" over the crack. Make sure that the patch is total hardened before putting is back on.

That's an idea. I'd bet even JB Weld would work. Mine was also cracked exactly like @Wano 's. I'm still using it on my 07. All I did was use a large washer to push down on the cracked portion. I don't recommend this as a solution alone as I might have a leak. I'd take it off, JB Weld it back together, after curing re-install it with a new gasket and two large washers (one on each stud) to prevent breaking again.

https://www.gmpartsdirect.com/oem-parts/gm-secondary-air-injection-pipe-cover-12574378

12574378 - Genuine GM Cover, Secondary Air Injection Pipe

GMPartsGiant.com offers the great deal for genuine GM parts, 12574378. Cover, Secondary Air Injection Pipe for $4.89. All parts are backed by the GM's warranty.

www.gmpartsgiant.com

Aren't these the right part?

Sometimes it's listed online but can be NLA in reality. You order it and they later cancel the order as NLA. Most parts for this platform from GM are out of production.

However, they seem to be plentiful on eBay:

12574378 for sale | eBay

Get the best deals for 12574378 at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

And again, another option is to find a used one from a yard.

 

[TollKeeper]

There are a bunch of them available on eBay..

12574378 in eBay Motors for sale | eBay

www.ebay.com

Edit: This appears to be the cheapest one, at just at $10 bucks shipped, with decent transit time.

Pardon Our Interruption...

 

[Wano]

I saw that part number (12574378) from earlier responses here, but when I entered the vehicle information on Ebay it said "does not fit your vehicle"... so that kinda threw me off so I didn't order it. But hey... you guys know a hell of a lot more than this old dude so I'm ordering that right now. Again, I appreciate everyone's help. It really helps my situation and how my day goes.

 

[budwich]

I'm still hoping that when I do replace this plate then the 02 sensor "not ready" will go away and the smog test will get past that point

I think you might want to get your codes read somewhere / somehow. I am not sure that the "plate issue" would cause a monitor (o2) to not set. It might but there should be codes of some type associated with the issue. My guess is that you have some sort of o2 issue. Further, was the engine work done in CA or in another state? Not a US person, but I would have thought that there would be an issue running without that system or "modding" the truck to over come it... but maybe the 02 model didn't have the air injector system.

 

[Mooseman]

The 2002 did not have the air injection system. In fact, it didn't appear until 2006. And it could cause an O2 sensor issue as a leak could allow air into the exhaust stream and throw it off. If that doesn't fix it, then yes, look into why that monitor isn't setting but it does take a little while. The evap system usually takes the longest time to complete.

 

[christo829]

My 04 has/had it. It was a complete nuisance when the exhaust valve developed a leak that allowed moisture to build up down at the air injection pump which then froze and rusted. It was delightful to delete it.
I did notice back then that it took quite a while for the O2 sensors to report ready. Unfortunately, I did not take before and after deletion "time to ready" readings. Things seem fairly normal now, and it did just pass VA emissions.

 

[Mooseman]

My 04 has/had it.

My bad. I went by RA's parts listing and it showed 06+ because I went according to my 07. Looking deeper, some of the valves show 2002-2005 for particular part numbers from the cheap/unknown brands and 2004-2005 for ACDelco and known brands. Very odd but not surprising that part compatibility lists being wrong . I am fairly certain that 02-03 did not have it.

 

[budwich]

The 2002 did not have the air injection system. In fact, it didn't appear until 2006. And it could cause an O2 sensor issue as a leak could allow air into the exhaust stream and throw it off. If that doesn't fix it, then yes, look into why that monitor isn't setting but it does take a little while. The evap system usually takes the longest time to complete.

I was referring to the monitor not being set / ready. The issue of cracked plate Is likely to cause an O2 issue (leaning report).... but not sure how there are no codes, hence the suggestion of checking.

Further, I don't see how a CA truck has this "mod" without some form of pcm flash.

 

[Mooseman]

It's not a mod. It came from the factory like that. My 02 EXT was the same. The SAIS wasn't introduced until 2004. His is a 2002.

 

[TollKeeper]

Might be an 02, but the manifold could have been replaced?

 

[Wano]

This 2002 Envoy SLE was purchased here in CA, and the rebuild/install from Jasper was completed here as well. It passed smog during registration when I purchased it of course, and it also passed last year. This year has been the headache. Ordered the block plate and gasket separately from Ebay and just waiting on the parts. Would a 50-100 mile drive after replacing the block plate allow enough drive time to see if the computer attempts or "trys" to correct the 02 sensor "not ready" ?

 

[mrrsm]

Welcome to GMT Nation...

FWIW... Here are the... OEM Drive Cycle Procedures Specific to YOUR Vehicle ...as presented in the Snap-On Modis Diagnostic Scan Tool... Professional Instructions. YMMV with variations in Pro-Grade Scan Tools... but THIS information is generally nested within your GMC 2002 Envoy Service Shop Manual...which may be MORE complete. Refer to Yours after downloading it from THIS Link:

Need service manuals? Get them here!

*********************************************************** The password below is no longer required. I am unable to edit that post to remove that info. Please note that the FireFox browser has issues with the password handling and because these downloads are not under HTTPS, flagging them as...

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[mrrsm]

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[Mooseman]

Might be an 02, but the manifold could have been replaced?

The SAIS port is in the head just above the manifold.