What did you do to your NBS GMT800 Tahoe/Yukon Today?

yukon-coRn · Apr 26, 2026

mountie said:
Maybe the headlight switch??

Could be that, or the relay. Going to poke around today once the crotch goblins are fed

yukon-coRn · Apr 26, 2026

Lo and behold, everything is working normally today. ‍

mountie · Apr 26, 2026

yukon-coRn said:
Lo and behold, everything is working normally today. ‍

Take today off.

6speedblazer · Apr 26, 2026

Jumped on another project today. I was determined to save my ext back glass over buying a Chinese replacement.

This is avalanche/ext specific but the rear window frames crack and eventually leak. We'll its a real soft plastic trim on the glass and all I can think is that it shrinks over time because mine was broken and did not fit over the glass. I had no missing pieces as the frame off the glass fits together perfect.

So I took the frame off and cleaned everything real good and figured out my cuts and put it back together. Then used 2 part epoxy to fill in the gaps from where it shrunk. After the epoxy dried i did a skim coat of rtv to level the surfaces and fill in any imperfections in the expoy.

Also fixed my defrost tabs, as the solder joints failed as the frame walked around.

Waiting for everything final cure over night then I will give it a good once over and put it back in the truck.

mikez71 · Apr 28, 2026

Checked codes today with VCM Scanner (HPTuners) instead of the Tech2..
Only showed P0332 knock sensor code.. (Ohmed the harness, definitely bad sensor)

Took a closer look at my Tech2 freeze frame screen shots..

My P0332 Knock Sensor code says 'Freeze Frame Data' on top.
My P0101 MAF code says 'Failure Record Data' on top.

They were shown on the same screen in the Tech2...
Hoping it was just a history code from my old MAF, that doesn't clear until enough drive cycles?!

yukon-coRn · Apr 28, 2026

Yanked this 9" screen monstrosity from the dash. My trim bezel had a few pre-broken tabs too

mountie · Apr 28, 2026

yukon-coRn said:
Yanked this 9" screen monstrosity from the dash. My trim bezel had a few pre-broken tabs too

View attachment 483886

No more “Tesla look” anymore !!

Brrdog93 · Apr 29, 2026

Today I replaced plugs, wires and coils on my 05 Tahoe LT.

Fless · Apr 29, 2026

Drove it to do some errands, and to top off the fuel with 20.4 gallons of premium (91 octane here). It'll get emissions done in a month or so and we'll see how it does if they do the treadmill test like they have the past two times, although those were on E85 and it passed with flying colors.

For now, at 9% alcohol, the fuel trims are within 3% all around. Won't be long until it hits 119k on the clock.

mattbta · Apr 29, 2026

Fless said:
Drove it to do some errands, and to top off the fuel with 20.4 gallons of premium (91 octane here). It'll get emissions done in a month or so and we'll see how it does if they do the treadmill test like they have the past two times, although those were on E85 and it passed with flying colors.

For now, at 9% alcohol, the fuel trims are within 3% all around. Won't be long until it hits 119k on the clock.

I know you've traditionally used the corn - is the switch to e10/15 a hedge on them putting the sniffer on and potentially being out of compliance?

I filled with e85: 22.087 gal @ $2.639. Same fuel cost $2.199 exactly two months ago.

Also not happy as with the Bosch fuel pump/sensor and upgraded OS, that was way more empty than I like.

Fless · Apr 29, 2026

mattbta said:
I know you've traditionally used the corn - is the switch to e10/15 a hedge on them putting the sniffer on and potentially being out of compliance?

I filled with e85: 22.087 gal @ $2.639. Same fuel cost $2.199 exactly two months ago.

Also not happy as with the Bosch fuel pump/sensor and upgraded OS, that was way more empty than I like.

Well, we have a temporary change of fuel, since my son just did a round trip to Dallas to help a friend move, and haul a trailer. We didn't want him to have to try to keep using E85 so he used premium all the way, since that's the canned tune that's on it and the mpgs towing are bad enough without the even worse E85 numbers.

Today's pump price for 91 octane was $4.89, but I had a 90 cent discount from grocery store points, so I used it. I haven't seen what E85 is costing lately, but I know that it's up. It doesn't get driven much so I doubt that it'll use any more than a half tank or so before emissions.

Our emissions tests are required every other year; the past two times they've put the Hoe on the treadmill and used the sniffer. I don't mind that so much since I get to see real numbers (same cost, but up now to $35 for the test). But sometimes they just use the OBD data to verify. I'm not worried at all about it since it runs fine on either fuel, but after this year's test we'll switch back. And I'd like to see how the emissions do on gas. Just curiosity on my part.

mikez71 · Apr 30, 2026

Drove my Suburban thinking things were finally going to get better.

No P0332 (because I spliced front knock sensor for both signals. temp fix. still saw 2.4 degrees of knock earlier in the day)
No P0101 (because I replaced the MAF and it was hopefully just a history code afterwards)

-BUT- the TRANSMISSION decides to slam shift 1-2 and 2-3..
Felt like the drivetrain was going to fall out of the truck.. Could feel it through my steering wheel..
Shifted like that about a mile before it went back to normal..

It's going to be a long road before I can trust this vehicle.. Probably won't be worth the fix..
Guess it's time to start logging transmission parameters....?

mattbta · Apr 30, 2026

Fless said:
Well, we have a temporary change of fuel, since my son just did a round trip to Dallas to help a friend move, and haul a trailer. We didn't want him to have to try to keep using E85 so he used premium all the way, since that's the canned tune that's on it and the mpgs towing are bad enough without the even worse E85 numbers.

Today's pump price for 91 octane was $4.89, but I had a 90 cent discount from grocery store points, so I used it. I haven't seen what E85 is costing lately, but I know that it's up. It doesn't get driven much so I doubt that it'll use any more than a half tank or so before emissions.

Our emissions tests are required every other year; the past two times they've put the Hoe on the treadmill and used the sniffer. I don't mind that so much since I get to see real numbers (same cost, but up now to $35 for the test). But sometimes they just use the OBD data to verify. I'm not worried at all about it since it runs fine on either fuel, but after this year's test we'll switch back. And I'd like to see how the emissions do on gas. Just curiosity on my part.

We've never had sniffer test in the counties I've lived in since starting driving, just the OBD-II checks. I would also be curious to see actual results, too.

mikez71 · Apr 30, 2026

The best results I've ever had on a sniffer test was a 1979 Dodge powerwagon! Carb'd 360 engine 727 trans.

I don't know how or why, but the numbers were super low. Engine did run very smoothly.. And I don't remember the tech having to rev the piss out of the engine or anything.. but maybe my memory is off..

And I had an '85 MR2 1.6L not pass! (But found the cat was replaced with one that had a 1" thick core, passed after replaced)

They got rid of sniffer test here in CA around 20 years ago I think?

strutaeng · Apr 30, 2026

mikez71 said:
Drove my Suburban thinking things were finally going to get better.
No P0332 (because I spliced front knock sensor for both signals. temp fix. still saw 2.4 degrees of knock earlier in the day)
No P0101 (because I replaced the MAF and it was hopefully just a history code afterwards)

-BUT- the TRANSMISSION decides to slam shift 1-2 and 2-3..
Felt like the drivetrain was going to fall out of the truck.. Could feel it through my steering wheel..
Shifted like that about a mile before it went back to normal..

It's going to be a long road before I can trust this vehicle.. Probably won't be worth the fix..
Guess it's time to start logging transmission parameters....?

It's doing hard shifting?

If there's a problem with the MAF (for example, if you accidently leave it unplugged when removing/reinstalling the intake tube), the transmission get maximum line pressure commanded and those are the hard shifts. Once I removed my transmission on my 06 to do a RMS and one of the speed sensors wiring insulation had cracked and the wires shorted out, with similar results on the shifting, but I did have a code set for that.

But you just stated the MAF code was gone, so IDK why it did that?

Fless · Apr 30, 2026

mikez71 said:
The best results I've ever had on a sniffer test was a 1979 Dodge powerwagon! Carb'd 360 engine 727 trans.

I don't know how or why, but the numbers were super low. Engine did run very smoothly.. And I don't remember the tech having to rev the piss out of the engine or anything.. but maybe my memory is off..

And I had an '85 MR2 1.6L not pass! (But found the cat was replaced with one that had a 1" thick core, passed after replaced)

They got rid of sniffer test here in CA around 20 years ago I think?

Our sniffer test is always done with the vehicle doing varied rpms on a treadmill. The plain OBD test is just that, nothing in the tailpipe.

mikez71 · Apr 30, 2026

Fless said:
Our sniffer test is always done with the vehicle doing varied rpms on a treadmill. The plain OBD test is just that, nothing in the tailpipe.

Same, they used to test on the rollers here, but now it's mostly a bunch of visual and obd checks. But it's possible they didn't put 4WD's on rollers.. Maybe just AWD, but I wouldn't be surprised if they applied that to 4WD just in case..

I don't even know if they check the tailpipe now, because I get bored watching them poke around the engine compartment and quit paying attention...

mikez71 · Apr 30, 2026

strutaeng said:
It's doing hard shifting?

If there's a problem with the MAF (for example, if you accidently leave it unplugged when removing/reinstalling the intake tube), the transmission get maximum line pressure commanded and those are the hard shifts. Once I removed my transmission on my 06 to do a RMS and one of the speed sensors wiring insulation had cracked and the wires shorted out, with similar results on the shifting, but I did have a code set for that.

But you just stated the MAF code was gone, so IDK why it did that?

Just for a stretch last night. Otherwise shifts perfectly fine as far as I can tell.

P0894 code..

Tech 2 says 'transmission component slipping'.... online searches mention possibility of sticky valves...
Only thing I notice in my logs so far, sometimes the 1-2 nd 2-3 shift time error will be 6.4s, usually 0s.. I don't notice any 6 second delay!
I saw another thread where half the wires going into transmission connector lost all insulation! LS1tech thread showed this....

But I don't see in that thread mention of any codes..
And I see nicktransmissions mention on another board that slip codes in a 4l80 are usually TCC or valve body related.

I may start a thread and ask his input after I crawl under there and inspect the harness...

mikez71 · May 1, 2026

I tried wiring up a radio output splitter, like I did in my GMT-900 to bypass the chimes...
BUT on the GMT-800 the stinking chimes come through EVERY door..

Off to disable the key-in-ignition switch I suppose..
When I'm done with all this low hanging BS, I get to look for a transmission.. Yay!

mountie · May 1, 2026

I just ordered that cargo liner from Canvasback….. ( One piece, 8’ long w/ the 60-40 split for the 2nd row seats. )
Goody…...

What did you do to your NBS GMT800 Tahoe/Yukon Today?

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