What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[George B]

I have been in the back with the panels off and my tech2 in hand it worked as commanded with the tech2, there are only 2 actuators in the rear. the one nearest the rear blower motor controls hot/cold and the one further up at the Y in the vents controls air up/down, you can put in the wrong actuator it will fit, plug in and everything, it just will not work right (i know because I tried it lol). so assuming you have the correct actuators in there it could something else like a bad control module or faulty sensor in the vent, there are 2 thermistors in the same rear vent area where the actuators are, they should have 5volts power at the harness and the sensor should change resistance when heat is applied (like from a hair dryer or heat gun), it's unlikely one of them would be bad but if you are in there may as check them to rule it out.View attachment 265748 View attachment 265749

Thanks, I will have to play with it more I guess. It’s confusing because it works to a point and heats/cools when it should but not as warm as it should in my opinion. I will have to figure out which sensor is which back there. The tech 2 lists 4 of them.

I could swear I remember someone mentioning something working backwards with the tech2 clone in special functions.

 

[Doubeleive]

Thanks, I will have to play with it more I guess. It’s confusing because it works to a point and heats/cools when it should but not as warm as it should in my opinion. I will have to figure out which sensor is which back there. The tech 2 lists 4 of them.

I could swear I remember someone mentioning something working backwards with the tech2 clone in special functions.

I was back there troubleshooting mine because I was getting cold air in the back when I put it on heat, unless I had it set all the way up to full heat, if I turned it down 1 degree it would blow cold, the tech2 kept telling me there was a sensor feedback error, I searched high and low for that dam "sensor", even paid for a diagram which oddly enough came from a amazon website that showed a air sensor up in the headliner drivers side rear near the rear hatch which did not exist on my truck. I finally figured out that the main hvac control I had bought from rockauto had the wrong firmware and I had to have it reprogrammed to my vin, this was before I had ever tried to program with the tdsweb and the tech2 and didn't want to brick my bcm or something, once the hvac control was reprogrammed everything worked fine again.
one thing I learned from that is if you do a full scan with the tech2 it will try to find ANY option that may exist on a gm vehicle and if it does not find one of those options it will tell you no communication with that module. It does not know if you have it or not it just say's hey can't communicate, so this can be misleading if you are not sure if you have that module, sensor, etc or not.
getting back to those little sensors I pictured there is like 6-8 or even 10 of them in these trucks I am still not sure exactly it depends on if it is swb or lwb, they are all over most of them are in the front air vents. I found 2 in the rear vents one is pretty accessible when you have the rear hvac passenger side panel off the other is more forward and you have to take the passenger side mid pillar cover off to access it, if the tech2 say's there are 4 there could be 2 more in the vents more up in the headliner or down under the carpet.
previous experience tells me you may just have a lazy actuator if you are not getting warm enough air, especially if the tech2 says there is a "feedback error" I had that problem on the front passenger side it would not blow the same temperature as the drivers side, replaced the actuator and problem solved.

 

[Doubeleive]

what you can do is just watch the actuator as you control the hvac without tech2 connected, manually adjust your heat/cold and watch the actuator move, if you set the hvac to full heat the door should be fully closed at the mark on the actuator, if it isn't then the actuator motor is probably funky.

 

[1BADI5]

Well I'm off to the dyno.

Since they did not confirm til this morning, I did not install the injectors or set up a tow.

I'm just going to drive to the shop and hot swap the injectors in the parking lot before the tune. I guess the upside is I'm saving $125 on not having a tow.

Numbers to follow later gents

 

[1BADI5]

Well I'm off to the dyno.

Since they did not confirm til this morning, I did not install the injectors or set up a tow.

I'm just going to drive to the shop and hot swap the injectors in the parking lot before the tune. I guess the upside is I'm saving $125 on not having a tow.

Nu

 

[iamdub]

Well I'm off to the dyno.

Since they did not confirm til this morning, I did not install the injectors or set up a tow.

I'm just going to drive to the shop and hot swap the injectors in the parking lot before the tune. I guess the upside is I'm saving $125 on not having a tow.

Nu

You're so excited you double-tapped the Post button.

 

[George B]

I was back there troubleshooting mine because I was getting cold air in the back when I put it on heat, unless I had it set all the way up to full heat, if I turned it down 1 degree it would blow cold, the tech2 kept telling me there was a sensor feedback error, I searched high and low for that dam "sensor", even paid for a diagram which oddly enough came from a amazon website that showed a air sensor up in the headliner drivers side rear near the rear hatch which did not exist on my truck. I finally figured out that the main hvac control I had bought from rockauto had the wrong firmware and I had to have it reprogrammed to my vin, this was before I had ever tried to program with the tdsweb and the tech2 and didn't want to brick my bcm or something, once the hvac control was reprogrammed everything worked fine again.
one thing I learned from that is if you do a full scan with the tech2 it will try to find ANY option that may exist on a gm vehicle and if it does not find one of those options it will tell you no communication with that module. It does not know if you have it or not it just say's hey can't communicate, so this can be misleading if you are not sure if you have that module, sensor, etc or not.
getting back to those little sensors I pictured there is like 6-8 or even 10 of them in these trucks I am still not sure exactly it depends on if it is swb or lwb, they are all over most of them are in the front air vents. I found 2 in the rear vents one is pretty accessible when you have the rear hvac passenger side panel off the other is more forward and you have to take the passenger side mid pillar cover off to access it, if the tech2 say's there are 4 there could be 2 more in the vents more up in the headliner or down under the carpet.
previous experience tells me you may just have a lazy actuator if you are not getting warm enough air, especially if the tech2 says there is a "feedback error" I had that problem on the front passenger side it would not blow the same temperature as the drivers side, replaced the actuator and problem solved.

what you can do is just watch the actuator as you control the hvac without tech2 connected, manually adjust your heat/cold and watch the actuator move, if you set the hvac to full heat the door should be fully closed at the mark on the actuator, if it isn't then the actuator motor is probably funky.

I am going to start a thread on this one I guess.
I suspect a control issue but will try to work through all the settings from each control and report findings. It will probably be a slow moving thread since my Wife has little appetite for me doing too much wrenching right now.

 

[Just Fishing]

Dropped off my head at the welder yesterday.
I was hoping he was going to give it a quick try to extract the bolt with me waiting, but nope!
Looks like I'm in line behind a transfer case or something along those lines.

His new backyard shop is pretty amazing.
His old shop was amazing but this one is much bigger.

Maybe my cylinder head will get a video, if that's the case then i wish i cleaned up the exhaust ports before dropping it off.

Here is hoping it's done sometime this weekend...

 

[Geotrash]

It will probably be a slow moving thread since my Wife has little appetite for me doing too much wrenching right now.

It's a good thing to have a wife who enjoys your company enough to want you around. I have that too, and so the work on the trucks happens when I can get to it. Sometimes she comes out and helps, just to be together.

 

[pwtr02ss]

Dropped off my head at the welder yesterday.
I was hoping he was going to give it a quick try to extract the bolt with me waiting, but nope!
Looks like I'm in line behind a transfer case or something along those lines.

His new backyard shop is pretty amazing.
His old shop was amazing but this one is much bigger.

Maybe my cylinder head will get a video, if that's the case then i wish i cleaned up the exhaust ports before dropping it off.

Here is hoping it's done sometime this weekend...

That should take like 2 minutes. My heads had two broken bolts. My brother had them out in no time. Welded a nut on and the came right out. Good luck with it