Tech2 Expert help needed. Question about HVAC on '04 Denali

[chevy529]

I'm not good with mine yet. By a long shot! So I need a little help here.
I'm not getting heat from my HVAC ... again.

When I command the Air inlet door to move (sitting at 6 count) it doesn't.

The Mode door goes up in count instead. What am I missing?

 

[Rocket Man]

I haven't messed with the HVAC with my texh2 yet but maybe @swathdiver will chime in. I'm pretty sure he has.

 

[swathdiver]

I haven't seen the exact screens for the NBS. If you're in special functions, it will have a section for each door to command. If your in the section to command the air inlet door, even though the others can be seen, they cannot be controlled unless you go into their section. Does that make sense? Then again, if the motor is bad or really stuck, it's not going to move. There are three symptom codes that can follow each trouble code to explain why the actuator is not working. Did you try the reset?

 

[chevy529]

I tried a re-calibration first and it "seemed" to work. As in, it changed to the starting temp. then changed from defrost to panel to floor etc. I couldn't hear the actuators moving exactly as it was raining.

I think I understand what you mean. You are saying that you have to enter the exact screen for that particular door? I controlled the others from the main screen.
On the main screen I can control the others by highlighting them and commanding them on, then off. The count raises to equal desired state. EXcept the Air Inlet Door. When I try to command THAT door, the Mode door count goes up instead.

Baffled me.

I'm old and easily confused.

No heat but no codes.
Antifreeze is fine. Heater lines are equal temp. Intermittent. Engine temp at desired degrees

But I'm gonna hook it up again today and try something else.
I quit before I punched my window out. Seemed prudent.

 

[swathdiver]

Does the manual shed any light on the heating issue? Remember on the old GM cars, it was that brass valve with the vacuum line hose, sometimes the vacuum line would rot away, sometimes the valve got stuck and needed a little finesse from a channel lock to get going again. I don't even know how ours works yet.

 

[chevy529]

I followed the diagnostic steps in the manual and it led me to ... flush the heater core. What?!

Which is probably what led the shop I took it to last winter to do the same thing. Who charged me $385 after I told them it had to be an actuator problem. I was choked!
If your lines in and out are the same temp it isn't the heater core unless this has a TRULY unique system.

I think it must be a chafed wire occasionally touching, but what I don't understand is why it doesn't set a code ... of some kind. Maybe they don't?

I'm in the wrong mood to get on it again today. When I'm frustrated I stop thinking critically.

 

[chevy529]

I tried to come at it from a different way last night. Got into HVAC/Data Display/Sensor Data. The Sensor Data screen came up for 1 second then it disappeared and it said "wrong vehicle". So I backed out of the screens to double check I had the correct vehicle. I did. Walked though the screens and the same thing happened. WTH! So I tried a CAdillac Escallade. Same thing.

@swathdiver Have you ever been into that screen?

Oh and Happy National Holiday weekend to everyone in North America!

 

[swathdiver]

I tried to come at it from a different way last night. Got into HVAC/Data Display/Sensor Data. The Sensor Data screen came up for 1 second then it disappeared and it said "wrong vehicle". So I backed out of the screens to double check I had the correct vehicle. I did. Walked though the screens and the same thing happened. WTH! So I tried a CAdillac Escallade. Same thing.

@swathdiver Have you ever been into that screen?

Yes! Just to be sure, I went outside fired up the truck and Tech2 and tried it out. Went right in to that and every other menu option there. Any DTCs in the HVAC module? If you back out of there to the main menu, select the last option F3, Vehicle Control Systems, and let it run through all of your modules. Now my trucks lists 29 modules and says I cannot communicate with some. The reason is, they are not there! I do not side blind zone alert, retractable running boards, electronic suspension, the smart amp, etc. But if it cannot communicate with your HVAC, I would say then that the module is bad. While you're there, let the Tech2 look for trouble codes which you can then look up in each module.

Thanks Shannon, looking forward to Independence Day! As I type, my neighbors are already celebrating, lots of fireworks going off! Should I join them?

 

[chevy529]

Yes! Just to be sure, I went outside fired up the truck and Tech2 and tried it out. Went right in to that and every other menu option there. Any DTCs in the HVAC module? If you back out of there to the main menu, select the last option F3, Vehicle Control Systems, and let it run through all of your modules. Now my trucks lists 29 modules and says I cannot communicate with some. The reason is, they are not there! I do not side blind zone alert, retractable running boards, electronic suspension, the smart amp, etc. But if it cannot communicate with your HVAC, I would say then that the module is bad. While you're there, let the Tech2 look for trouble codes which you can then look up in each module.

Thanks Shannon, looking forward to Independence Day! As I type, my neighbors are already celebrating, lots of fireworks going off! Should I join them?

Thanks James! Did you join them? Have all your hair?
I feel sorry for families with little kids where I live. The city fireworks show is on tonight up here but full dark doesn't come till 11:00 p.m. I'm betting there will be some cranky kids tomorrow. IF they manage to stay awake for it.

There aren't ANY DTC's. After I fixed my ride height sensor I cleared that one. Nothing there now. For anything.
I'm going to use my phone to see what that screen says before it disappears. Too fast for me to focus on. I've done a full diagnostic run a few times. I'm guessing you are probably right about it being the control module. Now I just have to figure out how to test it to be sure. Multi meter time I guess.

I just remembered something. When I go into that module a screen comes up that says digital radio not responding. Continue?
I press yes and it carries on. It does that when I look at a few modules.
I have the Premium amp and my radio works. Does everything run through it?

I want my '97 back! lol

EDIT: I lied. I have one for ABS but one thing at a time. The sensor is probably rust jacked as there is no signal lol So, let's see, fix sunroof that won't close properly, fix ABS that isn't getting a signal or the EBCM is fubared, fix HVAC that isn't getting heat to the front.

I just fixed the bent front bumper arm and broken fog light holder. Thanks RockAuto. My Father must have pulled too close to a snow bank and didn't notice it.
The broken control arm on the RR ride height sensor was $64 CDN and only available from GM. Screw that. A piece of 1/8" Redi-Rod and 4 - 1/8" ball joints. Drilled out the Metric holes to 1/8". Cut to length, install, threadlock the nuts and Boom Bang, both sides better than new. Plastic ball joint ends on factory arm? Brilliant! Not!

All in ... about $45 and a couple hours messing around.

 

[swathdiver]

Thanks James! Did you join them? Have all your hair?
I feel sorry for families with little kids where I live. The city fireworks show is on tonight up here but full dark doesn't come till 11:00 p.m. I'm betting there will be some cranky kids tomorrow. IF they manage to stay awake for it.

There aren't ANY DTC's. After I fixed my ride height sensor I cleared that one. Nothing there now. For anything.
I'm going to use my phone to see what that screen says before it disappears. Too fast for me to focus on. I've done a full diagnostic run a few times. I'm guessing you are probably right about it being the control module. Now I just have to figure out how to test it to be sure. Multi meter time I guess.

I just remembered something. When I go into that module a screen comes up that says digital radio not responding. Continue?
I press yes and it carries on. It does that when I look at a few modules.
I have the Premium amp and my radio works. Does everything run through it?

I want my '97 back! lol

I think I'm staying inside this year, save for cooking on the grill! I saw that pile of rockets in the back of @Doubeleive Denali and decided I better not go near them! LOL

The screen that comes up and goes away real quick is the regular screen. It goes away quick because there's a problem or if you do not have that option. That happens to me when I pull up the amp, side blind zone, etc. Yours is disconnected, bad wire, or broken. As for the digital radio, I get that with our 2004 Montana. The radio works and van runs fine so I never bothered to investigate.

As for the Premium Amp, all the speakers connect to it and then goes to the radio if memory serves. You should have the wiring diagrams for that in your shop manual. @kbuskill